Count 'em, that's five occultations, signals Marc Buie, leader of the mission.
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Incredibly, the astronomers managed to capture not one but five occultations of MU69.
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And to make it even tougher, the occultations are happening during daytime hours.
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But be aware that only certain parts of the world will be able to see particular occultations.
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Here are the best places to see the lunar occultations, according to the International Occultation Timing Association.
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These eclipsing events, known as occultations, have allowed the mission scientists to better understand the true shape and size of the object.
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They also used the Cassini spacecraft&aposs voyage to Saturn to study occultations of the moon until the mission&aposs end last September.
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Even if you have no shot at spotting this event, consider how useful occultations can be for scientific study of our solar system.
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There will be four more Moon-Mars occultations this year, although this is the only one that will be visible from North America.
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Occultations can occur between the moon and planets, with pairs of planets and also when planets or the moon cross paths with far away stars.
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Hazy eclipses at SaturnWith 21990 confirmed moons, Saturn's skies offer myriad eclipse-viewing opportunities, from tiny solar transits to massive occultations to moons stacked atop other moons.
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Arimatsu and his colleagues examined the observations for signs of occultations, the term for slight dips in stellar brightness caused by objects passing in front of stars.
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This year, astronomers observed several occultations of a distant star by a space rock called 2014 MU69, which is floating about a billion miles away from Pluto.
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Members of the New Horizons team crisscrossed oceans and continents, hoping to observe these occultations when the stars briefly vanished as MU69 passed in front of them.
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Just remember: orbital alignments used for occultations are rare and usually don't repeat, so they take a huge amount of planning—which means you'll only get one shot.
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When you're in the right place, with the right viewing equipment, lunar occultations can be quite breathtaking, like the one that occurred in 2007 when the moon occulted Saturn.
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And indeed, Buie said the occultations made earlier this week wouldn't have been possible without the help of Argentinian scientists, government officials, and locals—many of whom went beyond the call of duty.
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As a consolation for those in North America who won't be able to see the occultations, you can still try to catch a celestial alignment between Mercury, Mars, Regulus and Venus, in that order, before sunrise.
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Image: NASA/JPL/Space Science InstituteIn 2014, analyzing visible and infrared spectra collected by Cassini during solar occultations, researchers demonstrated that Titan absorbs, refracts, and scatters sunlight in ways that may obscure information about deeper parts of the atmosphere.
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"A binary with a smaller moon might...help explain the shifts we see in the position of MU69 during these various occultations," said Marc Buie, a New Horizons team member from the Southwest Research Institute in Boulder, Colorado, in a statement.
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It turned out that a bonanza of three such events, which are known as occultations, were expected to occur within a two-month period this year, on June 269, July 123 and July 212, as MU269 passed in front of three different stars.
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To date there have been two reported Philomelian stellar occultations.
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There have been 9 occultations observed since 1988, many of which are multichord occultations. The best is the July 19, 2011 event observed from 57 stations spread out along the western USA coast where 46 stations recorded positive occultations and 11 stations observed misses. However many of the misses were important to clearly separate the two components of 90 Antiope. Alas, many planned stations were clouded.
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The archive of lunar occultations observations, (1623 to the present day) are maintained at VizieR.
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Malena Rice and Gregory Laughlin have proposed that a network of telescopes be built to detect occultations by Jupiter Trojans. The timing of these occultations would provide precise astrometry of these objects enabling their orbits to be monitored for variations due to the tide from Planet Nine.
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Previous occultations had been observed in 1983 and 1990, which produced a much larger size estimate of 81.4 km.
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The angular diameter of X Cancri has been measured using both lunar occultations and very long baseline interferometry, both methods giving a diameter around .
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Such occultations occur when the Moon's ascending node is near the autumnal equinox. A series of 49 occultations occurred starting on 29 January 2015 and ending at 3 September 2018. Each event was visible from points in the northern hemisphere or close to the equator; people in e.g. Australia or South Africa can never observe an Aldebaran occultation since it is too far south of the ecliptic.
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Some members take part in regular observations of variable stars, lunar occultations, sunspots, meteors, comets, and other phenomena; others develop special skills such as astroimaging at workshops.
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It is 5.39 degrees north of the ecliptic, so it can be occulted by the Moon. Such occultations occur when the Moon's ascending node is near the vernal equinox, as was the case in 2007. Most occultations are visible only in the Southern Hemisphere, because the star is at the northern edge of the lunar occultation zone. Rarely, it may be occulted as far north as southern California.
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This group is named after 234 Barbara, which polarimetric properties and observed occultations suggest that such bodies have an unusual shape and topographic features with large concave areas.
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In 1947 he was elected the first official president of the Astronomical League. Besides his numerous variable star observations he was interested also in solar astronomy and occultations.
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David Stanley Evans (28 January 1916 – 14 November 2004) was a British astronomer, noted for his use of lunar occultations to measure stellar angular diameters during the 1950s.
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Publications by Slocum included "Occultations of the Pleiades by the moon on February 14, 1932" (Astronomical Journal 1932), and "The eclipsing binary WW Aurigae" (Lick Observatory Bulletin 1942).
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An occultation diameter of ~170 km was measured from the observations. Since then two more occultations have been observed, which give an estimated mean diameter of ~150 km for diameter.
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Occultations with the moon have not yet confirmed the existence of the second suspected companion. However, component A is a barium star which would tend to confirm this unseen component.
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Lightcurve data from Hertha indicates a flattened body, and radar observations indicate that Hertha is non-metallic. Five occultations of stars by the asteroid have been observed between 2000 and 2015.
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HST Saturn portrait from 20 June 2019 From time to time, Saturn is occulted by the Moon (that is, the Moon covers up Saturn in the sky). As with all the planets in the Solar System, occultations of Saturn occur in "seasons". Saturnian occultations will take place monthly for about a 12-month period, followed by about a five-year period in which no such activity is registered. The Moon's orbit is inclined by several degrees relative to Saturn's, so occultations will only occur when Saturn is near one of the points in the sky where the two planes intersect (both the length of Saturn's year and the 18.6-Earth year nodal precession period of the Moon's orbit influence the periodicity).
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These transits and occultations can be used to analyse both the nebula and the object passing in front of it, by observing how radiation from the nebula is altered by the transiting body.
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Another 7-inch refractor of newer design, a special H-alpha telescope and a 16-inch Newtonian telescope are located in separate sheds on the terrace between the two astrodomes. The latter telescope is frequently used by the members of the association for their scientific research – predominantly the observation of star occultations by minor planets. The results are sent to a Japanese institute. For observations made by the Stuttgart Observatory concerning occultations, the observatory code given by the Minor Planet Center is 025.
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Existence of the atmosphere of Pluto was proven via stellar occultation. If a star is occulted by a body without an atmosphere, its light disappears sharply, but occultations by Pluto show a gradual decrease.
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Since 1991, the asteroid has been observed in stellar occultation a total of 6 times, all but one were single chord occultations. A 2006 double chord observation indicated a diameter of 126.6 +/-8.3 km.
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Mutual occultations or transits of planets are extremely rare. The most recent event occurred on 3 January 1818, and the next will occur on 22 November 2065. Both involve the same two planets: Venus and Jupiter.
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From Germany, this total eclipse could not be seen with clouded sky except by few observers at Pomerania only.ON THE ECLIPSES AND OCCULTATIONS SEEN IN GERMANY IN THE PAST Capel Lofft observed this eclipse from Ipswich.
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In 1861, the brightness of 56 Melete was shown to vary by German astronomer Friedrich Tietjen. To date, two stellar occultations by Melete have been observed successfully (in 1997 and again in 2002). Melete has been studied by radar.
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Since 1999 there have been four stellar occultations by the asteroid. The first three were single chord observations, and the fourth was a 3-chord observation, and a miss. The best fit ellipse measures 60.0x74.0 kilometres at PA -14degrees.
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Antares B can sometimes be observed with a small telescope for a few seconds during lunar occultations while Antares is hidden by the Moon. Antares B appears a profound blue or bluish-green color, in contrast to the orange-red Antares.
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The word "transit" refers to cases where the nearer object appears smaller than the more distant object. Cases where the nearer object appears larger and completely hides the more distant object are known as occultations. In astronomy, planetary transits and occultations occur when a planet passes in front of another object, as seen by an observer. The occulted object may be a distant star, but in rare cases it may be another planet, in which case the event is called a mutual planetary occultation or mutual planetary transit, depending on the relative apparent diameters of the objects.
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Later occultations in 2013 and 2014 yielded mean diameters of and , respectively. The mean diameter of , calculated from both chords from the occultations, appears seemingly consistent with the Spitzer and Herschel thermal measurement of . While the apparent oblateness of Varuna could not be determined from the single chord obtained from the 2014 occultation, the 2013 occultation yielded two chords, corresponding to an apparent oblateness of approximately 0.29. The imposed oblateness for the 2013 chord length of as Varuna's diameter corresponds to a polar dimension of approximately , somewhat consistent with the calculated 2010 minimum polar dimension of .
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Both northern and southern poles spend 42 years in a complete darkness, and another 42 years in continuous sunlight, with the sun rising close to the zenith over one of the poles at each solstice. The Voyager 2 flyby coincided with the southern hemisphere's 1986 summer solstice, when nearly the entire southern hemisphere was illuminated. Once every 42 years, when Uranus has an equinox and its equatorial plane intersects the Earth, mutual occultations of Uranus's moons become possible. In 2007–2008 a number of such events were observed including two occultations of Titania by Umbriel on August 15 and December 8, 2007.
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The actual observations revealed none of the four predicted occultations, likely due error measuring orbital period of Thorondor, although photometry data gathered during observation campaign have allowed to determine Manwë is highly bilobate contact binary, likely surrounded by rapidly orbiting moonlets besides Thorondor.
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It was predicted that 449 occulted the star HIP 1424 in July 2013.Asteroid Occultation Updates Stellar occultations can allow a chord to be calculated An asteroid occulation was predicted for 18 Oct 2018 with the magnitude 12 star UCAC4-557-042266.
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In 1927 the light was modified to a fixed white light, with regular occultations. For this purpose a mechanical clockwork device was installed. In 1953 the lighthouse began to use gas to fuel the light, with acetylene gas being introduced in 1958.
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TAOS is sensitive to occultations by Kuiper Belt Objects (KBOs) larger than about 500 m in diameter Z.-W. Zhang, F. B. Bianco, M. J. Lehner, N. K. Coehlo, J.-H. Wang, S. Mondal, C. Alcock, T. Axelrod, Y.-I. Byun, W.-P.
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3 Geminorum can be occulted by the Moon. Observations of these occulations can give information about the angular diameter of a star, or about close companions. Occultations of 3 Geminorum have been observed, but no double or diameter information has been published.
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The second part contained data for the meridian of Washington on the Sun, Moon, planets, principal stars, eclipses, occultations, and other phenomena. Beginning in 1882, data for Mercury, Uranus, and Neptune was added to the first part, with eclipses, occultations, and other phenomena forming a separate third part. In 1916, The American Nautical Almanac ceased to be a reprint of the first part of the American Ephemeris and Nautical Almanac, becoming a separately prepared volume for the navigator. In 1937, the American Ephemeris and Nautical Almanac was divided into seven parts, with data for the meridian of Washington substantially reduced, then eliminated beginning in 1951.
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Four first magnitude stars, Regulus, Spica, Antares, and Aldebaran, are sufficiently close to the ecliptic that they may be occulted by the Moon. In addition, two star clusters visible to the naked eye, the Beehive Cluster and the Pleiades, are often occulted. Depending on one's location on the Earth, there are usually several occultations involving naked eye objects every year and many more that can be observed using binoculars or a telescope. Accurate timings (accuracy at least +/-0.02 seconds) of lunar occultations are scientifically useful in fields such as lunar topography, astrometry, and binary star studies and are collected by the International Occultation Timing Association - IOTA.
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As a result of a 1997 lunar occultation, a companion star was discovered at an angular separation of 21 mas. It appears to be an A-type main sequence star with a class of around A5. This companion was not detected during prior occultations by the Moon.
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The spectrum of this asteroid matches a M-type asteroid. It may be the remnant of an asteroid that had undergone differentiation, with orthopyroxene minerals scattered evenly across the surface. There is no indication of hydration. To date, there have been at least two observed occultations by Liberatrix.
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The second book is on astronomy. Here Theon affirms the spherical shape and large size of the Earth; he also describes the occultations, transits, conjunctions, and eclipses. However, the quality of the work led Otto Neugebauer to criticize him for not fully understanding the material he attempted to present.
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Unusual light variation during these occultations has been explained as the result of a possible close companion. The companion would be just over one magnitude fainter and separated by 0.01 arcsec. The companion has not been detected by any other means although it should be easily detected with modern observations.
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In this way, a solar eclipse is an occultation of the Sun. Because the Moon is comparatively close to Earth, occultations of individual stars are not visible everywhere on the planet, nor at the same time. Because of the precession of the lunar orbit, each year different stars are occulted.
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It is consistent with theoretical data, which predict fast mixing of the atmosphere. But there is evidence for small vertical heterogeneities in temperature. They reveal themselves in sharp and brief spikes of brightness during stellar occultations. Amplitude of these heterogeneities is estimated to be on the scale of a few km.
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He was a professor at Faculdad de Ingeniera de San Juan from 1948 until 1955. His astronomical studies included southern double stars, variable stars, occultations, asteroids and comets. On November 8, 1942 he may have discovered Nova Puppis 1942. In 1958 he became the first president of the Asociación Argentina de Astronomía.
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Eight kilometers high in the atmosphere near the tropopause, the winds change direction. They now flow to the west and are driven by differences in temperature between the poles and equator. These high winds may distort Triton's atmosphere making it asymmetric. An asymmetry was actually observed during star occultations by Triton in 1990s.
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A diagram of the SUSIM instrument. SUSIM measured ultraviolet (UV) emissions from the sun. The observations are made both through vacuum and through occultations of the sun through the atmosphere. This allowed a comparison of the amount of UV light that reaches the earth and the amount absorbed by the upper atmosphere.
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A stellar occultation by in December 2018 gave a minimum diameter of 458 km. In 2018, two stellar occultations by were observed on 3 February and 24 December. Observations of the February occultation yielded a single chord length of . Observations of the December occultation yielded two positive chords, which suggest an approximate diameter of for .
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Following claims by David Dunham in 1978 to have detected satellites for some asteroids (notably 532 Herculina) by examining the light patterns during stellar occultations, Van Flandern and others began to report similar observations.Van Flandern, T. C., Tedesco, E. F. & Binzel, R. P. in Asteroids (ed. Gehrels, T.) 443–465 (Univ. Ariz. Press, Tucson, 1979).
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Peitho (minor planet designation: 118 Peitho) is a main-belt asteroid. It is probably an S-type asteroid. It was discovered by R. Luther on March 15, 1872, and named after one of the two Peithos in Greek mythology. There have been two observed Peithoan occultations of a dim star: one was in 2000 and the other in 2003.
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Both Atala and Céluta are American Indian fictional characters.; An occultation of a star by Atala was observed from Japan on 11 March 1994. Subsequent occultations have been observed as recently as 2006. Photometric of this asteroid made in 1981 gave a light curve with a period of 5.282 ± 0.004 hours with a brightness variation of 0.50 in magnitude.
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The star is situated near the ecliptic and thus is subject to lunar occultations. This is an aging K-type giant star with a stellar classification of K4III. Having exhausted the supply of hydrogen at its core, it has cooled and expanded off the main sequence. At present it has 41 times the girth of the Sun.
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10µ radiometric data collected from Kitt Peak in 1975 gave a diameter estimate of 114 km. Since 1985, a total of three stellar occultations by Antigone have been observed. A favorable occultation of a star on April 11, 1985, was observed from sites near Pueblo, Colorado, allowing a diameter estimate of 113.0 ± 4.2 km to be calculated.
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Stellar occultations by Fortuna have been observed several times. Fortuna has been studied by radar. It was discovered by J. R. Hind on August 22, 1852, and named after Fortuna, the Roman goddess of luck. Fortuna has been perturbed by the 80 km 135 Hertha and was initially estimated by Baer to have a mass of 1.08 kg.
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Minnesota Astronomy Review Volume 18 – Fall 2003/2004 Audio Version of Star of Bethlehem by Karlis Kaufmanis Archaeologist and Assyriologist Simo Parpola has also suggested this explanation.Simo Parpola, "The Magi and the Star," Bible Review, December 2001, pp. 16-23, 52, and 54. In 6 BC, there were conjunctions/occultations (eclipses) of Jupiter by the Moon in Aries.
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Daniel Barbier (10 December 1907 – 1 April 1965) was a French astronomer born in Lyon. Between 1930 and 1965 he published nearly 100 scientific papers on astronomy. Among his works were studies of stellar atmospheres and lunar occultations and eclipses. He performed studies of the upper atmosphere, Aurora Borealis, the zodiacal light and the night airglow.
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50 Aquarii, abbreviated 50 Aqr, is a single star in the zodiac constellation of Aquarius. 50 Aquarii is its Flamsteed designation. It is a faint star with an apparent visual magnitude of 5.76 that is barely visible to the naked eye under good seeing conditions. The star is located near the ecliptic and thus is subject to lunar occultations.
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Over the years there have been various activities related to astronomy: observation of sunspots, variable star observing, astrophotography, supernova search, observation of comets, occultations, teaching courses, the public open days, etc. Undoubtedly the main activity of the Observatory San Jose, faithful to the purpose for which it was founded, is the teaching and dissemination of astronomy.
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They also determined the distances of stars from their parallaxes - the very small apparent annual motions as the Earth orbited the Sun. Many of these results were published as star catalogues. Spencer Jones's own research concentrated on the motions of the Earth and the Moon. He refined knowledge of the Moon's orbit using observations of occultations of stars.
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Tupman maintained his interest in astronomy, and reported numerous occultations between 1885 and 1900. He was on the Council of the Royal Astronomical Society (1873–1880), and was also appointed its Secretary (1884–1889). He also established the Hillfoot Observatory in Harrow, and enjoyed helping visitors to make observations. Tupman's interests later in life included wireless telegraphy.
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The Amateur Astronomers Association of Pittsburgh, Inc. (AAAP) has promoted popular astronomy in western Pennsylvania for over seventy five years. With over 500 members, it is one of the larger astronomy clubs in the nation. At monthly meetings (open to the public) upcoming celestial events such as meteor showers, comets, occultations, and rare planetary alignments are announced.
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The symmetry of the secondary occultations and multiple observations of the event in various locations helped reconstruct not only the shape and size of the object, but also the thickness, orientation, and location of the ring planes. The relatively consistent ring properties inferred from several secondary occultation observations discredit alternative explanations for these features, such as cometary-like outgassing.
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Kamil Hornoch became interested in astronomy in 1984. One year later he started with his scientific observations of comets, meteors, the solar photosphere, variable stars, the planets and occultations. He lives in Lelekovice, a village in the South Moravian Region, the Czech Republic. Hornoch makes most of his observations from a small observatory in Lelekovice with a reflector telescope.
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74 Virginis is a single star in the zodiac constellation of Virgo. It is visible to the naked eye as a faint red-hued star with an apparent visual magnitude of 4.69. The star is positioned near the ecliptic and thus is subject to lunar occultations. The measured annual parallax of provides a distance estimate of around 400 light years from the Sun.
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On 19 February 2019, between 5:11 and 5:32 UTC, Jürgenstock occulted the star Sirius in the constellation Canis Major, the brightest star in the night sky. The shadow crossed Southern Argentina, Southern Chile, Central America, and the Caribbean. Occultations are typically an excellent method to determine a minor planet's dimension (cross-section) by exactly measuring the duration of the event.
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Near the altitude it reaches , and then slowly decreases. Pluto is the only trans-Neptunian object with a known atmosphere. Its closest analog is the atmosphere of Triton, although in some aspects it resembles even the atmosphere of Mars. The atmosphere of Pluto has been studied since the 1980s by way of earth-based observation of occultations of stars by Pluto and spectroscopy.
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During later occultations (when the atmosphere of Pluto was already denser) this kink was absent. Another evidence of the haze was obtained in 2002 due to a new occultation. The stellar light which managed to reach Earth during the occultation (due to refraction in Pluto's atmosphere), demonstrated an increase of intensity with wavelength.At least, in infrared range — from 0.75 to 2 µm.
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Tau2 Aquarii (τ2 Aqr, τ2 Aquarii) is the Bayer designation for a star in the equatorial constellation of Aquarius. It is visible to the naked eye with an apparent visual magnitude of +4.0. Because the star lies near the ecliptic it is subject to occultations by the Moon. This is an orange-hued giant star with a stellar classification of K5 III.
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The proposed Whipple spacecraft mission is designed to determine the outer limit of the Kuiper belt and directly detect Oort cloud objects out to 10,000 AU. Such objects are too small to detect with current telescopes except during stellar occultations. The proposal involves use of a wide field of view and rapid recording cadence to allow detection of many such events.
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An example of an occultation is when the Moon passes between Earth and the Sun, causing the Sun to disappear either entirely or partially. This phenomenon is commonly known as a solar eclipse. Occultations in which the larger body is neither the Sun nor the Moon are very rare. More frequent, however, is an occultation of a planet by the Moon.
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It is located near the ecliptic and thus is subject to lunar occultations. The cluster is located 2,050 light years away. Estimates for the number of cluster members range from 169 up to 414, with a directly-counted mass of ; by application of the virial theorem. The cluster is around 330 million years old with a near-solar metallicity of [Fe/H] = −0.04.
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The mean diameter of this object is estimated as 45.6 km. It has a rotation rate of 26.5 hours, or a little over a day. Observations of light curves and stellar occultations suggest the surface exhibits large concave areas. Polarimetric study of this asteroid reveals anomalous properties that suggests the regolith consists of a mixture of low and high albedo material.
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In addition, occultations at solstices probe hotter equatorial stratosphere. The visible magnitude of Uranus in two spectral bands (upper graph) adjusted for the distance, effective microwave temperature (middle graph) and the stratospheric temperature (lower graph). Blue band is centered at 470 nm, yellow at 550 nm. However, there are some reasons to believe that seasonal changes are happening in Uranus.
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Alauda has been observed to occult stars on several occasions, providing important information on its size and shape. It produced occultations on 2001-07-12 and 2004-04-21. It may have occulted an apparent magnitude 9.5 star in the constellation of Gemini on 2009-10-17 at 08:18 UT. This event should have been visible from Uruguay, Argentina, and Chile.
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Kelvin Mariner's Compass Charles Babbage had been among the first to suggest that a lighthouse might be made to signal a distinctive number by occultations of its light, but Thomson pointed out the merits of the Morse code for the purpose, and urged that the signals should consist of short and long flashes of the light to represent the dots and dashes.
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Another radio source, 3C 273, was predicted to undergo five occultations by the Moon. Measurements taken by Cyril Hazard and John Bolton during one of the occultations using the Parkes Radio Telescope allowed Maarten Schmidt to find a visible counterpart to the radio source and obtain an optical spectrum using the Hale Telescope on Mount Palomar. This spectrum revealed the same strange emission lines. Schmidt was able to demonstrate that these were likely to be the ordinary spectral lines of hydrogen redshifted by 15.8%, at the time, a high redshift (with only a handful of much fainter galaxies known with higher redshift). If this was due to the physical motion of the "star", then 3C 273 was receding at an enormous velocity, around , far beyond the speed of any known star and defying any obvious explanation.
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This unique feat brought worldwide acclaim and publication of his photographs. Tezel's other specialty in night sky photography is capturing rare conjunctions and occultations of bright stars, planets and bright clusters near the Moon. He also creates dramatic all-sky and time-lapse photographs that capture meteors and the motions of the cosmos. Photographing retrograde motions of planets has been one of his trademarks.
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A total of 17 stellar occultations by Hygiea have been tracked by Earth-based astronomers, including two (in 2002 and 2014) that were seen by a large number of observers. The observations have been used to constrain Hygiea's size, shape and rotation axis. The Hubble Space Telescope has resolved the asteroid and ruled out the presence of any orbiting companions larger than about in diameter.
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75 Tauri is a single, orange-hued star in the zodiac of constellation Taurus. It is a dim star but visible to the naked eye with an apparent visual magnitude of 4.96. Based upon an annual parallax shift of 17.47 mas as seen from Earth's orbit, it is located around 187 light years away. Due to its position near the ecliptic, it is subject to lunar occultations.
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Bardwell graduated from Mount Holyoke College in 1866 and remained to teach there for 33 years. She taught algebra, trigonometry, physics, and astronomy. She was also the director of the John Payson Williston Observatory at the college from its opening in 1881 until 1896, during which time she oversaw its growth. Improvements in telescopes allowed her and her students to observe sunspots, lunar occultations, and variable stars.
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The rings were thoroughly investigated by the Voyager 2 spacecraft in January 1986. Two new faint rings—λ and 1986U2R—were discovered bringing the total number then known to eleven. Rings were studied by analyzing results of radio, ultraviolet and optical occultations. Voyager 2 observed the rings in different geometries relative to the sun, producing images with back-scattered, forward-scattered and side-scattered light.
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Rochester Institute of Technology Observatory is a small astronomical observatory owned and operated by Rochester Institute of Technology. It is located in Henrietta, New York, United States. The observatory is primarily used to teach undergraduate astronomy labs, although some research relating to cataclysmic variables and asteroid occultations also takes place. There are one telescope dome and one roll-off shed on the premises, both housing telescopes.
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Based upon photometric observations made between 2010 and 2014, this asteroid has a rotation period of 21.812 ± 0.001 hours and a brightness variation of 0.08 ± 0.01 in magnitude. At opposition, the absolute magnitude was measured at 7.45 ± 0.01. It displays a hemispheric albedo dichotomy similar to that on 4 Vesta. As of 17 September 2020, there have been thirteen observed occultations of stars by Eunike.
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In 1906 astronomer Vesto Slipher of Lowell Observatory discovered that Delta Capricorni A was a spectroscopic binary. The orbit was determined in 1921 by Clifford Crump using 69 radial velocity measurements obtained at Yerkes Observatory. However the eclipsing binary nature of the system was not discovered until 1956 by Olin J. Eggen at Lick Observatory. Lunar occultations have been observed in 1951, 1962, and 1988.
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Artemis (minor planet designation: 105 Artemis) is a main-belt asteroid that was discovered by J. C. Watson on September 16, 1868, at Ann Arbor, Michigan. It was named after Artemis, the goddess of the hunt, Moon, and crossways in Greek Mythology. Several Artemidian stellar occultations have been reported. An occultation of the star HD 197999 was observed in 1982, which gave an estimated chord length of 110 km.
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The star is drifting further from the Earth with a heliocentric radial velocity of +15.2 km/s. It is located near the ecliptic and thus is subject to lunar occultations. This is an aging giant/bright giant star with a stellar classification of G8II-III, and is most likely (97% chance) on the horizontal branch. It is around 350 million years old with 3.3 times the mass of the Sun.
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It is moving closer to the Earth with a heliocentric radial velocity of -3 km/s. 40 Aquarii is positioned near the ecliptic and thus is subject to lunar occultations. See p. 256. The stellar classification for 40 Aquarii is G5 IV, matching a G-type, yellow-hued subgiant star that has exhausted the supply of hydrogen at its core and has begun to evolve into a giant.
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This minor planet was named in memory of American astronomer Tom Van Flandern (1940–2009), expert in lunar occultations and on the dynamics of binary minor planets at USNO in the 1970s. Van Flandern also participated in the refinement of the Global Positioning System and published the Meta Research Bulletin for non-mainstream views on cosmology. The approved naming citation was published by the Minor Planet Center on 9 February 2009 ().
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The rings were investigated in detail during the Voyager 2 spacecraft's flyby of Neptune in August 1989. They were studied with optical imaging, and through observations of occultations in ultraviolet and visible light. The spaceprobe observed the rings in different geometries relative to the Sun, producing images of back- scattered, forward-scattered and side-scattered light.Forward-scattered light is light scattered at a small angle relative to solar light.
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Every several years, a period of mutual occultations occurs when the asteroid is viewed from Earth. Using Kepler's third law, the mass and density of the components can be derived from the orbital period and component sizes. The axis of the mutual orbit of the two components points towards ecliptic coordinates (β, λ) = (200°, 38°)Descamps et al., 2007, Icarus article published in April 2007 with 2 degrees uncertainty.
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Since 1988 there have been 8 reported stellar occultations by Juewa. From the occultation on 31 August 2013 the best fit ellipse measures 148.3+/-4.3 km x 142.3 +/- 15.6 km. 13-cm radar observations of this asteroid from the Arecibo Observatory between 1980 and 1985 were used to produce a diameter estimate of 172 km. Based upon radar data, the near surface solid density of the asteroid is 1.5.
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The SPA has a number of observing sections whose work members can participate in. These cover observations of aurorae, comets, deep sky, the Moon, meteors, occultations, the planets, the Sun and variable stars. The society publishes a magazine, Popular Astronomy, which from 2011 is being published every two months. Previously it was a quarterly publication, but it now includes material that was carried in now- defunct separate regular printed News Circulars.
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It is located 0.7 degree north of the ecliptic, and thus is subject to lunar occultations. The blue-white hued primary, component Aa, is a B-type main-sequence star with a stellar classification of B3V. It was found to be a close spectroscopic binary in 1903 by American astronomers Edwin B. Frost and Walter S. Adams. The pair have an orbital period of 2.96 days and eccentricity of 0.05.
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AEEA (Activities of Exhibition and Education in Astronomy) 天文教育資訊網 2006 年 7 月 11 日 Mu Ceti is an A9 giant star. It has been suspected to be a δ Scuti variable, but most studies find it to be of constant brightness. Three companions were all discovered during occultations of Mu Ceti by the Moon. An orbit was derived for the brightest with a period of 1202 days.
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Photometric observations of this asteroid in 1985 gave a light curve with a period of 9.127 ± 0.009 hours and a brightness variation of 0.29 ± 0.03 in magnitude. The curve is symmetrical with a single maxima and minima. This object has a spectrum that matches an XC classification; occupying the transition range between an X-type and a C-type asteroid. Eight occultations of stars by Lomia have so far been observed, between 2000 and 2018.
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The radar data produced an estimate of a maximum equatorial diameter of 94 km, which is consistent with earlier estimates based upon infrared data if the shape is assumed to be slightly elongated. The rotation period was further refined to during observations through 2010. Six stellar occultations of this asteroid between 2004 and 2007 produced chords ranging from 13–72 km (8–45 mi), which are statistically consistent with the published maximum diameter estimates.
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Twice during the orbital cycles of Jupiter and Saturn, the equatorial (and satellite) planes of those planets are aligned with Earth's orbital plane, resulting in a series of mutual occultations and eclipses between the moons of these giant planets. The terms eclipse, occultation, and transit are also used to describe these events. A satellite of Jupiter (for example) may be eclipsed (i.e. made dimmer because it moves into Jupiter's shadow), occulted (i.e.
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Observation of the satellite's orbit has made possible an accurate determination of Hermione's mass. For the best-fit "snowman" model, the density is found to be 1.8 ± 0.2 g/cm³, giving a porosity on the order of 20%, and possibly indicating that the main components are fractured solid bodies, rather than the asteroid being a rubble pile. Occultations by Hermione have been successfully observed three times so far, the last time in February 2004.
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X Cancri is a variable star in the northern constellation of Cancer. It has a red hue and is visible to the naked eye at peak magnitude, fluctuating around an apparent visual magnitude of 6.28. The distance to this object is approximately 2,900 light years based on parallax measurements, but is drifting closer with a radial velocity of −5 km/s. It lies very close to the equinox and so is subject to lunar occultations.
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Various sections exist within the Society to co-ordinate the activities of special interest groups, including the running of observational programs. They consist of the Comets and Meteor Section, Dark Sky, Deep-Sky, Education & Public Communication, Double Stars, Historical, Occultations, Solar and Variable Stars. A national Symposium, organised by one of the Centres, is held every second year. Scopex, a large public outreach event, is held every year under the auspices of the Johannesburg Centre.
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In 1984 an occultation of a star produced seven chords that Kristensen used to derive an ellipsoidal profile of 210×170 km. On 6 August 1989, Metis occulted a magnitude 8.7 star producing five chords suggesting a diameter of 173.5 km. Observations of an occultation on 11 February 2006, produced only two chords indicating a minimum diameter 156 km. (Chords) All three of these occultations fit the ellipsoid 222×182×130 km suggested by Baer.
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Membership in the SBAS is open to anyone 10 years of age or older, but only those of at least 16 years of age may vote and hold office. Members of all ages may participate in society activities. The society currently has a membership of more than 80 people. Society members contribute to the hobby of amateur astronomy via articles in astronomy publications, variable star observing, asteroid occultations, Astronomical League observing programs, and outreach events.
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Daniel Overbeek's serious interest in astronomy dates back to 1951, when he started observing occultations and variable stars. In 1958 he earned a B.Sc. degree in mathematics and astronomy from the University of South Africa. In his life he contributed 287,240 observations to the American Association of Variable Star Observers (AAVSO) International Database, becoming the most prolific AAVSO contributor. In 1998 he became the first amateur astronomer who detected supernova related gamma ray burst effects.
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The brightness of the star is diminished by 0.15 in magnitude from extinction caused by interstellar gas and dust. The star is positioned near the ecliptic and thus is subject to lunar occultations. This is an aging red giant star with a stellar classification of M0 III that is currently evolving along the asymptotic giant branch. Having exhausted the supply of hydrogen at its core, the star has expanded to 41 times the Sun's radius.
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Adapting to improvements in pharology, the type of fuel used by the burners has also changed. The original mineral oil was dropped in favour of petrol vapour, from 1898. In 1904 a second petrol burner was added. A foghorn was added on 15 November 1913. In 1939 the light characteristic was changed to 3 occultations (2 + 1) of white, red and green, then 5 white, red and green sectors, with a range of .
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These were occultations of the stars Spica and Beta Scorpii by the moon, a few nights apart. Ptolemy used these observations to confirm precession of the equinoxes, a phenomenon that had been discovered by Hipparchus in the 2nd century BCE. Sphaerica is the only book that has survived, in an Arabic translation. Composed of three books, it deals with the geometry of the sphere and its application in astronomical measurements and calculations.
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The tiny change in brightness of the system during these occultations will require at least a medium-aperture professional telescope for detection. Hiʻiaka last occulted Haumea in 1999, a few years before discovery, and will not do so again for some 130 years. However, in a situation unique among regular satellites, Namaka's orbit is being greatly torqued by Hiʻiaka, which preserved the viewing angle of Namaka–Haumea transits for several more years.
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139 Tauri is a single, blue-white hued star in the zodiac constellation of Taurus. It is faintly visible to the naked eye with an apparent visual magnitude of 4.81. The distance to this star, as determined from an annual parallax shift of , is roughly 1,600 light years. Because this star is located near the ecliptic, it is subject to occultations by the Moon. One such event was observed April 28, 1990.
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Phi Aquarii, Latinized from φ Aquarii, is the Bayer designation for a binary star system in the equatorial constellation of Aquarius. It is visible to the naked eye with a combined apparent visual magnitude of +4.223. Parallax measurements indicate its estimated distance from Earth is roughly , and it is drifting further away with a radial velocity of +2.5 km/s. The proximity of this star to the ecliptic means it is subject to lunar occultations.
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Via asteroid occultations: Observations of an occultation of a bright 5.5 magnitude star on 17 September 2002, produced seventy-five chords indicating an ellipsoid of 111×90 km. (Chords) Observations of an occultation on 15 November 2005, near Grass Valley, CA, produced five chords indicating an incomplete outline of 126×111 km. This larger result may be caused by a different orientation of the asteroid as it passed in front of the star.
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The word is often used in reference to the Sun, Earth, and either the Moon or a planet, where the latter is in conjunction or opposition. Solar and lunar eclipses occur at times of syzygy, as do transits and occultations. The term is often applied when the Sun and Moon are in conjunction (new moon) or opposition (full moon). The word syzygy is often used to describe interesting configurations of astronomical objects in general.
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32 Tauri is the Flamsteed designation for a solitary star in the zodiac constellation of Taurus. It has a visual magnitude of 5.64, making it visible to the naked eye from suburban skies (according to the Bortle scale). The position of this star near the ecliptic plane means that it is subject to occultations by the Moon. Parallax measurements with the Hipparcos spacecraft put it at a distance of roughly from the Sun.
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During the photometric observations in 2008, a minor-planet moon was also discovered, orbiting Wendelinefroger every hours at a distance of 8.7 kilometers. Based on mutual occultations of Wendelinefroger and its moon, the diameter ratio for the two bodies is at least 0.24 (i.e. secondary-to-primary mean-diameter ratio), which translates into an estimated diameter of 0.8 kilometer or more for the asteroid's moon, using CALL's calculated diameter for the primary.
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Two stellar occultations by Lucina have been observed so far, in 1982 and 1989. During the first event, a possible small satellite with an estimated 5.7 km diameter was detected at a distance of 1,600 km from 146 Lucina. A 1992 search using a CCD failed to discover a satellite larger than 0.6 km, although it may have been obscured by occultation mask. Further evidence for a satellite emerged in 2003, this time based on astrometric measurements.
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Australian amateur astronomer Jonathan Bradshaw recorded an unusual asteroid occultation by 32 Pomona on 16 August 2008. The expected maximum duration of the occultation was 7.1 secs; however, the video recording shows two separate occultations of equal depth each lasting 1.2 seconds, separated by 0.8 secs. Those durations convert to chord lengths at the asteroid of 15 km, 10 km, and 15 km – for a total length of 40 km. The IRAS diameter for Pomona is 80.8 ± 1.6 km.
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Occultations occur when Pluto passes in front of and blocks one of Pluto's satellites. Charon has an angular diameter of 4 degrees of arc as seen from the surface of Pluto; the Sun appears much smaller, only 39 to 65 arcseconds. Charon's proximity further ensures that a large proportion of Pluto's surface can experience an eclipse. Because Pluto always presents the same face towards Charon due to tidal locking, only the Charon-facing hemisphere experiences solar eclipses by Charon.
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18 Tauri is a single star in the zodiac constellation of Taurus, located 444 light years away from the Sun. It is visible to the naked eye as a faint, blue-white hued star with an apparent visual magnitude of 5.66. The star is moving further from the Earth with a heliocentric radial velocity of +4.8. It is a member of the Pleiades open cluster, which is positioned near the ecliptic and thus is subject to lunar occultations.
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49 Aurigae is a single star located 680 light years away from the Sun in the northern constellation of Auriga. It is visible to the naked eye as a dim, white-hued star with an apparent visual magnitude of 5.26. The star is moving away from the Earth with a heliocentric radial velocity of +17 km/s, having come to within some 5.5 million years ago. It is positioned near the ecliptic and thus is subject to lunar occultations.
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CE Tauri lies 4.6 degrees off the ecliptic. This makes it a candidate for occultations by the Moon and (extremely rarely) by one of the bright planets. The star's angular diameter has been measured by lunar occultation, giving limb-darkened visible light angular diameters of , , and . An occultation has also been observed in H-alpha, giving a diameter of , which indicates that there is circumstellar hydrogen producing emission across at least that size, nearly twice the visible diameter.
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The Far Ultraviolet Cameras experiment was to capture imagery and photometry of naturally occurring and man-made emission phenomena such as airglow and diffuse aurora. Secondary missions were to study interplanetary and interstellar objects (such as comets and stars) and to make atmospheric density measurements by stellar occultations. The instrument consisted of two imaging cameras and a low-light-level TV camera mounted on the same base. Like CIRRIS, they were controlled from the flight deck.
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Further research revealed that the temperature is strongly different in different regions: from 40 to . Around the year 2000, Pluto entered star-rich fields of the Milky Way, where it will reside until the 2020s. The first stellar occultations after 1988 were on 20 July and 21 August 2002 by teams led by Bruno Sicardy of the Paris Observatory and James L. Elliot of MIT. Atmospheric pressure turned out to be about 2 times higher than in 1988.
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During a sabbatical in 1940-1941, she traveled to Brazil to observe a solar eclipse, in a small team of scientists led by Charles Hugh Smiley; she wrote about her time in South America for Popular Astronomy.Farnsworth, Alice H. (1941). “An Astronomer’s Trip to South America,” Popular Astronomy 49: 405–418. Farnsworth's research involved stars in a region of the constellation Cassiopeia, and stellar photometry; she also continued the Williston Observatory's studies of sunspots and lunar occultations.
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However, ground-based results were inconclusive. Over the next six years, approximately 50 other occultations were observed with only about one-third of them yielding positive results. Something (probably incomplete arcs) definitely existed around Neptune, but the features of the ring system remained a mystery. The Voyager 2 spacecraft made the definitive discovery of the Neptunian rings during its fly-by of Neptune in 1989, passing by as close as above the planet's atmosphere on 25 August.
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HD 19789 is a double star in the northern constellation of Aries. The primary component has an orange hue and is barely visible to the naked eye with an apparent visual magnitude of 6.11. it is located at a distance of approximately 390 light years from the Sun based on parallax, and is drifting further away with a radial velocity of +8 km/s. The star is located near the ecliptic and thus is subject to lunar occultations.
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The position of this star near the ecliptic means it is subject to lunar occultations. This is an ordinary A-type main-sequence star with a stellar classification of A1 V, which indicates it is generating energy through hydrogen fusion at its core. It has 2.6 times the mass of the Sun and about 2.5 times the Sun's radius. The star is radiating 68 times the Sun's luminosity from its photosphere at an effective temperature of 9354 K.
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V4024 Sagittarii is a single variable star in the southern constellation of Sagittarius. It has a blue-white hue and is dimly visible to the naked eye with an apparent visual magnitude that fluctuates around 5.49. The star is located at a distance of approximately 1,700 light years based on stellar parallax, but is drifting closer with a radial velocity of −20 km/s. The position of this star near the ecliptic means it is subject to lunar occultations.
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The word "transit" refers to cases where the nearer object appears smaller than the more distant object. Cases where the nearer object appears larger and completely hides the more distant object are known as occultations. However, the probability of seeing a transiting planet is low because it is dependent on the alignment of the three objects in a nearly perfectly straight line. Many parameters of a planet and its parent star can be determined based on the transit.
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Wu, P. & van der Wal, W. Postglacial sealevels on a spherical, self-gravitating viscoelastic earth: effects of lateral viscosity variations in the upper mantle on the inference of viscosity contrasts in the lower mantle. Earth and Planetary Science Letters, Volume 211, Issues 1–2, June 15, 2003, Pages 57–68.Colwell, J. E., Esposito, L. W. & M. Sremcevic. Self-gravity wakes in Saturn’s A ring measured by stellar occultations from Cassini. Geophysical Research Letters, volume 33, April 1, 2006.
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On May 17, 2005, this asteroid occulted a faint star (magnitude 8.5) and the event was observed and timed in a number of locations within the U.S. and Mexico. As a result, a silhouette profile was produced, yielding a roughly oval cross- section with dimensions of 160 × 135 km (± 1 km).D.W. Dunham, "Upcoming Asteroid Occultations", Sky & Telescope, June, 2006, p. 63. The mass of the asteroid can be estimated based upon the mutually perturbing effects of other bodies, yielding an estimate of .
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McNaught worked at the University of Aston's satellite-tracking camera originally outside Evesham in 1982, thereafter at Herstmonceux and more recently at Siding Spring. In his spare time he successfully conducts patrols for novae, identifies images of prenovae and unusual variable stars on survey plates, measures their positions, makes astrometric observations of comets and minor planets and photometric observations of comets and novae. He also carries out extensive observational and computational work on meteors, as well as on occultations by minor planets.
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The club had regular observing sessions in Armfield's backyard, where there was an emphasis on scientific observation programs, especially variable stars, meteors, and lunar occultations. Notable early members were Edward A. Halbach, Walter Scott Houston, and William Albrecht. Growth would continue month by month and by the end of 1933, there would be 130 members. In January 1934 a member, M.J.W. Phillips offered an acre of land for the establishment of an observatory outside Milwaukee in the Town of New Berlin.
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In 1969, he received a Ph.D. in astronomy from Yale after completing his dissertation on lunar occultations. Van Flandern worked at the USNO until 1983, first becoming Chief of the Research BranchUSNO Staff Directory for Nautical Almanac Office, December 1976 and later becoming Chief of the Celestial Mechanics Branch of the Nautical Almanac Office.USNO Staff Directory for Nautical Almanac Office, November 1977 His espousal of highly non-mainstream beliefs, particularly the exploded planet hypothesis, eventually led to his separation from the USNO.
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It is positioned near the ecliptic and thus is subject to lunar occultations. This is an aging giant star with a stellar classification of K5 III, indicating it has exhausted the supply of hydrogen at its core then cooled and expanded off the main sequence. The stellar spectrum displays strong lines of cyanogen. It presently has 18 times the radius of the Sun and is radiating 102 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 4,324 K.
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Curves of pressure vs. distance from the center, obtained from occultations in 1988 and 2002, in combination with the now known radius of Pluto () give values of about for 1988 and for 2002. Spectral data provided values in 2008 and in 2012 for the distance from the center (1±4 km from the surface). An occultation on 4 May 2013 gave data almost precisely for the surface level (1190 km from the center, or 3±4 km from the surface): .
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Upsilon Capricorni, Latinized from υ Capricorni, is a solitary star in the southern constellation of Capricornus. It has a reddish hue and is dimly visible to the naked eye with an apparent visual magnitude of 5.17. The star is located at a distance of approximately 730 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −12 km/s. As it is positioned near the ecliptic, the star is subject to lunar occultations.
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A 2016 study of spiral density waves using stellar occultations indicated that the B Ring's surface density is in the range of 40 to 140 g/cm2, lower than previously believed, and that the ring's optical depth has little correlation with its mass density (a finding previously reported for the A and C rings). The total mass of the B Ring was estimated to be somewhere in the range of 7 to kg. This compares to a mass for Mimas of kg.
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A second circular structure was built in 1874 and in 1879 he built a second, larger circular observatory close to the old one. Tebbutt was a private astronomer and a fellow of the Royal Astronomical Society who continued to make patient, reliable astronomical observations and published regularly, building an international reputation. From the observatories he watched various astronomical phenomena - lunar occultations of stars, Jupiter's satellites, comets, minor planets, double stars, transits of Mercury and Venus - and his work won international acknowledgement.
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29 Cancri is a star in the zodiac constellation of Cancer, located 370 light years from the Sun. It is just visible to the naked eye as a dim, white-hued star with an apparent visual magnitude of 5.94. The star is situated near the ecliptic, which means it is subject to lunar occultations. This is an A-type main-sequence star with a stellar classification of A5 V, which indicates it is generating energy through hydrogen fusion at its core.
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Values for stellar radii vary significantly in different sources and for different observation methods. The angular diameters of many stars can be measured directly using stellar interferometry. Other methods can use lunar occultations or from eclipsing binaries, which can be used to test indirect methods of finding stellar radii. Only a few useful supergiant stars can be occulted by the Moon, including Antares A (Alpha Scorpii A). Examples of eclipsing binaries are Epsilon Aurigae (Almaaz), VV Cephei, and V766 Centauri (HR 5171).
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The position of this star near the ecliptic means it is subject to lunar occultations. The members of this system orbit each other with a period of and an eccentricity of 0.82. The visible component is a G-type subgiant star with a stellar classification of G5 IV. It is three billion years old and is spinning with a projected rotational velocity of 5.6 km/s. The star is radiating seven times the luminosity of the Sun from its photosphere at an effective temperature of 5,499 K.
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Observations of two multi-chord stellar occultations of 2010 and 2014 allow the matching of light curve inversions DAMIT model 1806 that give an equivalent-volume mean diameter of km, and an equivalent surface mean diameter of km. The density of Psyche derived from these estimates,, is consistent with that of other metallic asteroids. Observations of Psyche with Very Large Telescope's adaptive optics SPHERE imager revealed two large craters, which were informally named Meroe and Panthia, after the twin witches in the Roman novel Metamorphoses by Apuleius.
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81 Geminorum lies close enough to the ecliptic to undergo lunar occultations. The variable velocity of this system was first suspected at the Dominion Astrophysical Observatory in 1921, then confirmed by the Lick Observatory in 1922. It is a single-lined spectroscopic binary with an orbital period of and an eccentricity of 0.325. The visible component is an aging giant star with a stellar classification of K4 III, having exhausted the supply of hydrogen at its core then expanded to 34 times the Sun's radius.
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In 2013, reviewing the photometric data obtained in October 2005, Brian Warner found evidence that Tchantchès is possibly an asynchronous binary asteroid. Attenuations seen in the revised lightcurve indicated mutual occultations and eclipses events caused by a minor-planet moon orbiting Tchantchès. The satellite has an orbital period of 15.35 hours (2014 publication), and diameter of at least 25% of that of its primary. The Johnston's archive derives a satellite diameter of 510 meters and estimates a semi-major axis of 3.8 kilometers for its orbit.
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The optical depth of the λ ring shows strong wavelength dependence, which is atypical for the Uranian ring system. The equivalent depth is as high as 0.36 km in the ultraviolet part of the spectrum, which explains why λ ring was initially detected only in UV stellar occultations by Voyager 2. The detection during a stellar occultation at the wavelength 2.2 μm was only announced in 1996. The appearance of the λ ring changed dramatically when it was observed in forward-scattered light in 1986.
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The first three names come from "liberty, equality, fraternity", the motto of the French Revolution and Republic. The terminology was suggested by their original discoverers, who had found them during stellar occultations in 1984 and 1985. Four small Neptunian moons have orbits inside the ring system: Naiad and Thalassa orbit in the gap between the Galle and Le Verrier rings; Despina is just inward of the Le Verrier ring; and Galatea lies slightly inward of the Adams ring, embedded in an unnamed faint, narrow ringlet.
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Lally, Eugene F., "Mosaic Guidance for Interplanetary Travel". American Rocket Society, Astronautics, June 1962. Lally, Eugene F., "A Survey of Advanced Mosaic Guidance", Institute of Aerospace Sciences Summer Meeting, Los Angeles, California, June 19–22, 1962 His proposal was an array of electro-optical sensors connected to an on-board "computer" that would provide autonomous navigation by tracking the relative movement of stars and planetary occultations during space flight and planetary landings. All modern spacecraft navigation systems, such as "AutoNav", are derived from his proposals.
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The Society also got a planetarium ZKP-2 in 1970 and opened the Belgrade Planetarium with diameter of 8 m and 80 seats. Planetarium is mainly visited by the students of primary and high schools. Belgrade Planetarium During the 60s, 70s and 80s amateur astronomical observations of the Sun, occultations, binary and variable stars and planetary phenomena were regular. Too much light pollution around the Observatory in the last 5–10 years has limited Society's activities mainly on theoretical works and application of computers in astronomy.
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A stellar occultation in 2010 measured a single chord of . But this is only a lower limit for the diameter of because the chord may not have passed through the center of the body. In 2017, stellar occultations and data from its rotational lightcurve suggested that had an elongated shape, presumably due to its rapid rotation rate of 6.71 hours, similar to Haumea and Varuna. That would give approximate dimensions of 940 × 766 × 490 km, with its longest axis nearly twice as long as its polar axis.
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This is a case of mutual tidal locking, as compared to that of the Earth and the Moon, where the Moon always shows the same face to Earth, but not vice versa. The average distance between Charon and Pluto is . The discovery of Charon allowed astronomers to calculate accurately the mass of the Plutonian system, and mutual occultations revealed their sizes. However, neither indicated the two bodies' individual masses, which could only be estimated, until the discovery of Pluto's outer moons in late 2005.
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Because the star lies near the ecliptic it is subject to occultations by the Moon, allowing the angular size to be measured. As of 1940, the pair had an angular separation of 0.10 arc seconds along a position angle of 191°. The yellow-hued primary, component Aa, is an evolved G-type giant star with a stellar classification of G8.5 III and an estimated age of 4.3 billion years. It has 1.15 times the mass of the Sun and has expanded to 11.14 times the Sun's radius.
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The need to avoid ring material detected by stellar occultations resulted in this trajectory being abandoned and a trajectory that largely avoided the rings but resulted in more distant flybys of both targets. Voyager 2 spacecraft On 25 August, in Voyager 2 last planetary encounter, the spacecraft swooped only above Neptune's north pole, the closest approach it made to any body since it left Earth in 1977. When the spacecraft visited the Neptunian system, Neptune was the farthest known body in the Solar System.
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Althaea (minor planet designation: 119 Althaea) is a main-belt asteroid that was discovered by Canadian-American astronomer J. C. Watson on April 3, 1872, and named after Althaea, the mother of Meleager in Greek mythology. Two occultations by Althaea were observed in 2002, only a month apart. Based upon its spectrum, this is classified as an S-type asteroid. Photometric observations made in 1988 at the Félix Aguilar Observatory produced a light curve with a period of 11.484 ± 0.010 hours with a brightness variation of 0.365 ± 0.010 in magnitude.
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According to the surveys carried out by the NEOWISE mission of NASA's Wide- field Infrared Survey Explorer (WISE), the Infrared Astronomical Satellite IRAS, and the Japanese Akari satellite, Naëma measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0503 and a diameter of 54.05 kilometers based on an absolute magnitude of 10.2. Alternative mean-diameter measurements published by the WISE team include (), (), (), () and () with corresponding albedos of (), (), (), () and (). Several asteroid occultations of Naëma have been observed between 2002 and 2010.
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According to the surveys carried out by the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Backlunda measures () and () kilometers in diameter and its surface has an albedo of () and (), respectively. The Collaborative Asteroid Lightcurve Link assumes a standard albedo for carbonaceous asteroids of 0.057 and derives a diameter of 40.51 kilometers based on an absolute magnitude of 10.69. Alternative mean-diameter measurements published by the WISE team include (), (), (), () and () with corresponding albedos of (), (), (), () and (). Between 2003 and 2009, several asteroid occultations of Backlunda were observed.
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According to the surveys carried out by the Japanese Akari satellite, the Infrared Astronomical Satellite IRAS, and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), Ara measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. Alternative mean- diameters published by the WISE team include () and () with corresponding albedos of () and (). In 2009 and 2015, several asteroid occultations of Ara were observed. The two best-rated observations from January 2009 and April 2015 and August 2008, gave a best-fit ellipse dimension of () and (), respectively.
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Lightcurve observations in 2005 revealed that Lundia is a binary system of two similarly sized objects orbiting their common centre of gravity. "Lundia" now refers to one of the objects, the other being provisionally designated S/2005 (809) 1. The similarity of size between the two components is suspected because during mutual occultations the brightness drops by a similar amount independently of which component is hidden.Poznań observatory (Lightcurve showing signature of the binary) Due to the similar size of the primary and secondary the Minor Planet Center lists this as a binary companion.
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Subsequently, he developed methods and applications to facilitate the observation, timing and analysis. By 2010 he had switched to using sensitive video cameras, and began designing telescopes better suited to multi-station field work than what is commercially available, culminating in collapsible alt-alt telescopes of moderate size, compact enough to take anywhere in the world in standard airline baggage. In 2011 he formulated a method to derive asteroid dimensions by integrating the results of separate occultations. The tables are periodically updated and now include over 500 asteroids.
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CalSky (sky calendar) was web based astronomical calculator used by astronomers to plan observing. It was created by Arnold Barmettler a researcher at the University of Zurich and formerly a scientific assistant at the European Space Agency. The website, available in English and German, featured a calendar (and/or email notifications) generated for your location including information on aurora, comets, tides, solar and lunar eclipses, planets, bright satellite passes (ISS, HST, etc.), occultations, transits, iridium flares, and decaying satellites that may be visible. In 2020, the website ceased operation.
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CalSky (sky calendar) was a web-based astronomical calculator used by astronomers to plan observing. It was created by Arnold Barmettler, a researcher at the University of Zurich and formerly a scientific assistant at the European Space Agency. The website, available in English and German, featured a calendar (and/or email notifications) generated for your location including information on aurora, comets, tides, solar and lunar eclipses, planets, bright satellite passes (ISS, HST, etc.), occultations, transits, satellite flares, and decaying satellites that may be visible. In October 2020, the website ceased operation.
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De Gasparis "used his utmost endeavours to realise a 'Parthenope' in the heavens, such being the name suggested by Sir John Herschel on the occasion of the discovery of Hygiea in 1849". There have been two observed Parthenopian occultations, on 13 February 1987, and 28 April 2006. On 6 August 2008, during a perihelic opposition, Parthenope had an apparent magnitude of 8.8. In 1988 a search for satellites or dust orbiting this asteroid was performed using the UH88 telescope at the Mauna Kea Observatories, but the effort came up empty.
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The transit telescope would have been used to determine the latitude and longitude of the observatory, as well as regulating his chronometer by observing 'clock stars'; he may also have kept an astronomical clock. With his refractor telescope he could have observed eclipses and lunar occultations, monitored planets and comets, tracked separation and position of double stars, and searched for new variable stars – all common activities of amateur astronomers at the time with similar equipment. None of his records survive, however, and he published none of his observations.
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Shortly after his death in 2009, the asteroid 52266 Van Flandern was named in his honor because of his prediction and analysis of lunar occultations at the U.S. Naval Observatory and publications of papers on the dynamics of binary minor planets. He married Barbara Ann Weber (1942-2018) in 1963 in Kentucky, and they had 3 sons, Michael, Brian, and Kevin, and a daughter, Connie. The couple moved to Sequim, Washington from the East Coast in 2005 to be closer to their children and grandchildren.Barbara Ann (Weber) Flandern, Peninsula Daily News, Legacy.
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By recording the instant when the Moon occults a background star, (or similarly, measuring the angle between the moon and a background star at a predetermined moment) the lunar distance can be determined, as long as the measurements are taken from multiple locations of known separation. Astronomers O'Keefe and Anderson calculated the lunar distance by observing four occultations from nine locations in 1952. They calculated a mean distance of 384,407.6 ± 4.7 km ( ± ). This value was refined in 1962 by Irene Fischer, who incorporated updated geodetic data to produce a value of 384,403.7 ± 2 km ( ± ).
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Pressure of the atmosphere of Pluto is very low and strongly time-dependent. Observations of stellar occultations by Pluto show that it increased about 3 times between 1988 and 2015, even though Pluto has been moving away from the Sun since 1989. This is probably caused by Pluto's north pole coming into sunlight in 1987, which intensified evaporation of nitrogen from the northern hemisphere,In these sources this pole is called "south" according to nomenclature of that time. whereas its southern pole is still too warm for condensation of nitrogen.
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J1407b is the first exoplanet or brown dwarf discovered with a ring system by the transit method. A sequence of occultations (eclipses) of the star occurred over a 56-day period in 2007. The pattern was consistent with that expected for the transit of a large array of multiple rings, indicating the substellar companion dubbed “J1407b”. The J1407b ring system has an outer radius of approximately 90 million km (about 640 times the extent of Saturn’s rings). Cleared gaps in the rings indicate satellites (“exomoons”) have formed accreted from denser rings.
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42 Capricorni is located near the ecliptic and thus is subject to lunar occultations. This is a double-lined close spectroscopic binary with an orbital period of 13.174 days and an eccentricity of 0.18. The binary nature of this system was discovered in 1918 by the English astronomer Joseph Lunt. It has a combined spectrum that matches a stellar classification of G1 IV, with the individual components having estimated classes of G1 V and G2 V. This is an RS Canum Venaticorum variable, indicating the presence of an active chromosphere with star spots.
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The star is radiating 19 times the Sun's luminosity from its photosphere at an effective temperature of 8,274 K. Due to its location near the ecliptic, this star is subject to lunar occultations. These events have provided occasional, but not definitive, evidence of a close secondary companion. Eggleton and Tokovinin (2008) catalogue this as a possible triple star system, having the inner pair being similar stars with an angular separation of , and the outer component a magnitude 6.7 star of class F2 at a much wider separation of .
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A 2006 artist's impression of the SIM Lite predecessor, SIM PlanetQuest, design SIM Lite would have operated in an Earth-trailing heliocentric orbit, drifting away from Earth at the rate of 0.1 AU per year ultimately reaching a distance of 82 million km from Earth. This would have taken approximately years. The Sun would have continuously shone on the spacecraft, allowing it to avoid the occultations of target stars and eclipses of the Sun that would occur in an Earth orbit."SIM PlanetQuest ", Northrop Grumman, official site, 2004–2006.
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Two radio sources were involved 3C 48 and 3C 273 Measurements taken by Cyril Hazard and John Bolton during one of the occultations using the Parkes Radio Telescope allowed Maarten Schmidt to optically identify the object and obtain an optical spectrum using the 200-inch Hale Telescope on Mount Palomar. This spectrum revealed the same strange emission lines. Schmidt realized that these were actually spectral lines of hydrogen redshifted at the rate of 15.8 percent. This discovery showed that 3C 273 was receding at a rate of 47,000 km/s.
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After leaving East Sheen in 1821, William erected an observatory at South Kilworth that possessed a 36-inch focal-length altazimuth telescope, originally constructed by Edward Troughton for the St. Petersburg Academy of Sciences. The observatory was also equipped with a 42-inch focal-length achromatic refractor by Tulley, a transit circle by William Simms, and a clock by Hardy. While at South Kilworth, Pearson observed the occultations of the Pleiades in July and October 1821. In 1824 and 1829, he published the two quarto volumes of his Introduction to Practical Astronomy.
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Kepler's search volume, in the context of the Milky Way The motion of Kepler relative to Earth, slowly drifting away from Earth in a similar orbit, looking like a spiral over time Kepler orbits the Sun, which avoids Earth occultations, stray light, and gravitational perturbations and torques inherent in an Earth orbit. NASA has characterized Kepler's orbit as "Earth-trailing". With an orbital period of 372.5 days, Kepler is slowly falling farther behind Earth (about 16 million miles per annum). , the distance to Kepler from Earth was about .
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During this event, the observed brightness was predicted to dip from magnitude 14.7 (star + Chariklo) to 18.5 (Chariklo alone) for at most 19.2 seconds. This increase of 3.8 magnitudes is equivalent to a decrease in brightness by a factor 32.5. The primary occultation event was accompanied by four additional small decreases in the overall intensity of the light curve, which were observed seven seconds before the beginning of the occultation and seven seconds after the end of the occultation. These secondary occultations indicated that something was partially blocking the light of the background star.
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In 2007–2008 a number of such events were observed including two occultations of Titania by Umbriel on August 15 and December 8, 2007 as well as of Ariel by Umbriel on August 19, 2007. Currently Umbriel is not involved in any orbital resonance with other Uranian satellites. Early in its history, however, it may have been in a 1:3 resonance with Miranda. This would have increased Miranda's orbital eccentricity, contributing to the internal heating and geological activity of that moon, while Umbriel's orbit would have been less affected.
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A transit of a minor planet takes place when a minor planet passes directly between an observer and another heavenly body, obscuring a small part of that body's disc. From the perspective of observers on Earth, transits of the Sun and Moon by minor planets are very rare, as the minor planets orbiting between the Earth and those bodies are few and very small. Transits of the Sun would be more visible from the outer planets. Transits should be distinguished from occultations, in which the minor planet entirely blocks out the light from the other body.
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This is an evolved K-type giant star with a stellar classification of K4 IIIb. It has around 1.65 times the mass of the Sun and, at the age of three billion years, has expanded to 44 times the Sun's radius. The star is radiating 447 times the Sun's luminosity from its enlarged photosphere at an effective temperature of 3,963 K. Because Delta Piscium is positioned near the ecliptic, so it is subject to lunar occultations. It has a magnitude 13.99 visual companion at an angular separation of 135.0 arc seconds on a position angle of 12°, as of 2011.
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According to the surveys carried out by the NEOWISE mission of NASA's Wide- field Infrared Survey Explorer, the Infrared Astronomical Satellite IRAS, and the Japanese Akari satellite, Tauris measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. The Collaborative Asteroid Lightcurve Link adopts the results obtained by IRAS, that is, an albedo of 0.0470 and a diameter of 109.56 kilometers based on an absolute magnitude of 8.74. Alternative mean-diameter measurements published by the WISE team include (), (), () and () with corresponding albedos of (), (), () and (). Several asteroid occultations of Tauris were observed between 1999 and 2015.
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According to the surveys carried out by the Infrared Astronomical Satellite IRAS, and the Japanese Akari satellite, and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), Henrika measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. Alternative mean-diameters published by the WISE team include (), () and () with corresponding albedos of (), () and (). The Collaborative Asteroid Lightcurve Link derives an albedo of 0.1103 and a diameter of 19.15 kilometers based on an absolute magnitude of 11.6. An asteroid occultations of Henrika from 19 January 2010, gave a best-fit ellipse dimension of ().
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According to the surveys carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), the Japanese Akari satellite, and the Infrared Astronomical Satellite IRAS, Burnhamia measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0602 and a diameter of 66.64 kilometers based on an absolute magnitude of 9.55. The WISE team also published an alternative mean-diameter of () with corresponding albedos of (). Two asteroid occultations of Burnhamia September 2013 and January 2014, gave both a best-fit ellipse dimension of ().
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According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Alphonsina measures between 54.34 and 63.52 kilometers in diameter and its surface has an albedo between 0.204 and 0.2786. Combined Plot - Light Curve Inversion model (DAMIT 301) and Multi- chord Occultation. In 2003, stellar occultation measured a diameter of 59.2 kilometres and deduced an albedo of 0.218, while the modelling of asteroid occultation silhouettes gave a diameter of 58 kilometres. The asteroid has been observed in stellar occultations 8 times since 2003.
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Deviation of day length from SI based day with shorter days resulting from faster planetary rotation. Leap seconds are irregularly spaced because the Earth's rotation speed changes irregularly. Indeed, the Earth's rotation is quite unpredictable in the long term, which explains why leap seconds are announced only six months in advance. A mathematical model of the variations in the length of the solar day was developed by F. R. Stephenson and L. V. Morrison, based on records of eclipses for the period to , telescopic observations of occultations for the period 1623 until 1967 and atomic clocks thereafter.
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She also found a way to predict more occultations of the moon; these moments when the moon passed before other heavenly bodies were used to investigate the moon's orbit. Her new method for calculating solar eclipses allowed for a level of detail that could be used to understand the ionosphere. During this period, she participated in expeditions to view the solar eclipse of June 19, 1936 in Russia. Also, she organized and participated in the Hayden Planetarium-Grace Eclipse Expedition to Peru to view, photograph, and broadcast by radio the solar eclipse of June 8, 1937.
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Manwë and Thorondor were expected to go through a period of mutual occultations and transits from 2014–2018, where one object crosses in front of the other as seen from Earth. Pluto and Charon went through a similar series of mutual events from 1985–1990. Observations of these events could allow for better estimates of the radii of the two objects and their densities, as well as possibly determining their shapes and mapping surface color and albedo features. The first event, an inferior occultation, is predicted for 2014 July 16, and they continue until 2018 October 25.
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The star is positioned near the ecliptic and so is subject to lunar occultations. This is a B-type main-sequence star with a stellar classification of B9 Vn, where the 'n' indicates "nebulous" lines due to rapid rotation. It is 125 million years old with a projected rotational velocity of 335 km/s, completing a full revolution about its axis every . HD 23753 has been catalogued as a suspected variable star with the designation NSV 1321, although the amplitude is no more than 0.1 magnitude and it may even be suitable for a photometric standard.
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Eta Virginis looks single, but lunar occultations have shown it to be a very close triple star system consisting of two stars 0.6 AU apart, assuming a distance of 91 parsecs, with a third slightly more distant star. The inner pair is a spectroscopic binary that completes an orbit in 72 days. The inclination of this orbit was determined through interferometer observations to be 45.5°, allowing the masses of the two stars to be estimated. The primary star, Eta Virginis Aa, has a mass about 2.5 times the Sun's mass, while the secondary, Eta Virginis Ab, has 1.9 solar masses.
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The implication of this was that it was not the Moon that was speeding up – it was time (as measured in terms of Earth's increasingly long day) that appeared to be slowing down. Brown devoted much study to this problem and proposed it should be attacked observationally, using lunar occultations to map the Moon's path more precisely. He also reasoned that, if the discrepancies were caused by variations in the Earth's rotation, it implied that observations of other objects would be similarly affected. This was partially verified by observations of transits of Mercury, but Brown was initially not convinced.
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Evans left England in 1946 to work at the Radcliffe Observatory, Pretoria, South Africa when positional determinations and photometry were the main interests of the astronomical world, but when he left some twenty years later, the South African observatories had become active in astrophysics. Together with Harold Knox-Shaw he aluminised and installed the mirrors in the telescope. He determined the angular diameter of Antares and also wrongly came to the conclusion that Arcturus was elliptical in shape. This was later found to be an observational artifact, but the feasibility of measuring stellar diameters using lunar occultations, was soundly established.
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Its blue color points to a particle radius near 10 nm, but the ratio of brightnesses at different phase angles indicates a radius exceeding 100 nm. This can be explained by aggregation of small (tens of nm) particles into larger (hundreds of nm) clusters. The haze probably consists of particles of non-volatile compounds, which are synthesized from atmospheric gases under influence of cosmic high-energy radiation. The layers show the presence of atmospheric waves (presence of which is also suggested by observations of occultations), and such waves can be created by wind blowing over Pluto's rough surface.
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Previous attempted observations of stellar occultations by Varuna in 2005 and 2008 were unsuccessful due to uncertainties in Varuna's proper motion along with undesirable conditions for observing. In 2010, an occultation by Varuna was successfully observed by a team of astronomers led by Bruno Sicardy on the night of 19 February. The occultation was observed from various regions in southern Africa and north- eastern Brazil. Although observations of the occultation from South Africa and Namibia had negative results, observations from Brazil, particularly at São Luís in Maranhão, successfully detected a occultation by Varuna of an 11.1 magnitude star.
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On 24 May 1981, they detected a dip in a star's brightness during one occultation; however, the manner in which the star dimmed did not suggest a ring. Later, after the Voyager fly-by, it was found that the occultation was due to the small Neptunian moon Larissa, a highly unusual event. In the 1980s, significant occultations were much rarer for Neptune than for Uranus, which lay near the Milky Way at the time and was thus moving against a denser field of stars. Neptune's next occultation, on 12 September 1983, resulted in a possible detection of a ring.
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Assisted by a village mathematician named Ambrose Clarke, Pearson began the reobservation and computation of the 520 stars tabulated for occultations in his Practical Astronomy during the same year. He presented the resulting catalogue to the Royal Astronomical Society on 11 June 1841. Pearson observed Halley's comet on 29 October 1835, and in 1839 he deduced a value for the obliquity of the ecliptic from his own research. He died on 6 September 1847 at South Kilworth, and a tablet honoring his memory in the church recognizes the respect earned by his exemplary conduct as a clergyman and magistrate.
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What little is known about Timocharis comes from citations by Ptolemy in the Almagest. These indicate that Timocharis worked in Alexandria during the 290s and 280s BC. Ptolemy lists the declination of 18 stars as recorded by Timocharis or Aristillus in roughly the year 290 BC. Between 295 and 272 BC, Timocharis recorded four lunar occultations and the passage of the planet Venus across a star. These were recorded using both the Egyptian and Athenian calendars. The observed stellar passage by Venus may have occurred on October 12, 272 BC when the planet came within 15 arcminutes of the star η Virginis.
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Prokne (minor planet designation: 194 Prokne) is a main-belt asteroid that was discovered by German-American astronomer C. H. F. Peters on March 21, 1879, in Clinton, New York, and named after Procne, the sister of Philomela in Greek mythology. Stellar occultations by Prokne have been observed twice, in 1984 from Italy and again in 1999 from Iowa (United States). Observations from the W. M. Keck Observatory show the asteroid to be around 151 km across, with a size ratio of between the major and minor axes. For comparison, observations by the IRAS observatory gave a diameter of 164 km.
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The 250-680 nm spectral domain is used for the determination of O3, NO2, NO3−, aerosols and temperature. In addition, two high spectral resolution channels centred at 760 and 940 nm allow measurements of O2 and H2O and two fast photometers are used to correct star scintillation perturbations and to determine high vertical resolution temperature profiles. Global latitude coverage is obtained with up to 40 stellar occultations per orbit from South Pole to North Pole. Data acquired on dark limb (night-time) are of better quality than on bright limb (day-time) because of a smaller perturbation by background light.
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He is the author of more than 30 scientific articles, 250 astronomical telegrams and the presenter of talks at several international conferences. He has been an amateur astronomer since 1977, a member of the Moscow Astronomy Club since 2002 and the head of a working group on asteroidal occultations. He participated in Astrofests 2001–2006 and was a speaker at Astrofest 2005, 2006 and 2013. He is an active enthusiast of professional-amateur collaboration in astronomy and long-time contributor to IOTAoccultations, Planoccult, meteorobs, comets-ml, MPML, SeeSat, AAVSO-HEN, AAVSO-DIS, vsnet-alert, vsnet- outburst, cvnet-discussion mailing lists.
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Kepler's data in its first 1.5 years of operation was processed and analyzed, yielding Kepler-12b's radius, mass and density. The Spitzer Space Telescope's IRAC infrared adaptive optics camera was used to carry out program #60028, which observed the occultations by several giant planets detected by Kepler behind their host stars. The Kepler team, using the observations, tentatively concluded that Kepler-12b most likely did not experience a temperature inversion, in which the day-side temperature of the planet is lower than the night-side. Kepler-12b's discovery paper was published in the Astrophysical Journal on September 5, 2011.
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Lunar topography has considerable relief because of the presence of mountains, craters, valleys, and other topographical features. The irregularities of the lunar limb profile (the "edge" of the Moon, as seen from a distance) are known accurately from observations of grazing occultations of stars. Astronomers thus have a fairly good idea which mountains and valleys will cause the beads to appear in advance of the eclipse. While Baily's beads are seen briefly for a few seconds at the center of the eclipse path, their duration is maximized near the edges of the path of the umbra, lasting 1–2 minutes.
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James McMahon is an American amateur astronomer, acknowledged for his visual observations of asteroid occultations. In 1978 his observation of the occultation of the asteroid 532 Herculina with the star SAO 120774, together with photometric study made at the Lowell Observatory, was considered a proof of the existence of a Herculina's natural satellite, which would be the first discovery of an asteroid moon in history. However, a 1993 Hubble Space Telescope observation failed to confirm the discovery. In 1979 James McMahon was the first person awarded with the newly established Amateur Achievement Award of the Astronomical Society of the Pacific.
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Ate (minor planet designation: 111 Ate) is a main-belt asteroid that was discovered by the German-American astronomer C. H. F. Peters on August 14, 1870, and named after Ate, the goddess of mischief and destruction in Greek mythology. In the Tholen classification system, it is categorized as a carbonaceous C-type asteroid, while the Bus asteroid taxonomy system lists it as an Ch asteroid. Two stellar occultations by Ate were observed in 2000, only two months apart. The occultation of the star HIP 2559 by 111 Ate was used to determine a chord length of 125.6 ± 7.2 km through the asteroid, giving a lower bound on the maximum dimension.
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Antonia Ferrín Moreiras (Ourense, May 13, 1914 – Santiago de Compostela, August 6, 2009) was a mathematician, professor and the first female Galician astronomer. Her main contributions to astronomy were works on stellar occultations by the moon, measures of double stars and astrometric measurements, as well as the determination of the passage of stars through two verticals. She accomplished all of this while she was working at the Observatory of the University of Santiago de Compostela (USC). Before the Spanish Civil War, she obtained degrees in chemistry and pharmacy from the USC, earned her teaching diploma and studied Exact Sciences, the name for mathematics, for two years.
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According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), and the Japanese Akari satellite, Rotraut measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0506 and a diameter of 56.42 kilometers based on an absolute magnitude of 10.1. Alternative mean-diameter measurements published by the WISE team include (), (), () and () with corresponding albedos of (), (), () and (). Three asteroid occultations, observed on 30 November 2009, 22 September 2013 and 21 November 2015, gave a best-fit ellipse dimension of (), () (best), and (), respectively.
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According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the NEOWISE mission of NASA's Wide- field Infrared Survey Explorer (WISE), and the Japanese Akari satellite, Petropolitana measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. Alternative mean-diameters published by the WISE team include () and () with corresponding albedos of () and (). The Collaborative Asteroid Lightcurve Link, adopts the results obtained by IRAS, that is an albedo of 0.2382 and a diameter of 41.22 kilometers based on an absolute magnitude of 9.10. Two asteroid occultations of Petropolitana from May 2012 and September 2015, gave a best-fit ellipse dimension of () and (), respectively.
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According to the surveys carried out by the Japanese Akari satellite, the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), and the Infrared Astronomical Satellite IRAS, Seraphina measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0427 and a diameter of 59.75 kilometers based on an absolute magnitude of 10.16. Alternative mean-diameter measurements published by the WISE team include (), () and () with corresponding albedos of (), () and (). Two asteroid occultations of Seraphina gave a best-fit ellipse dimension of () and () for their respective observation on 5 February 2007 and on 20 July 2014.
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According to the survey carried out by the Infrared Astronomical Satellite IRAS, Gunila measures kilometers (km) in diameter and its surface has an albedo of . The Japanese Akari satellite gave a larger diameter of and an albedo of , as did various publications of the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, with diameters of or larger. The Collaborative Asteroid Lightcurve Link adopts the results from IRAS, and gives a diameter of 73.87 km with an albedo of 0.0477 based on an absolute magnitude of 9.58. Three asteroid occultations between 2006 and 2014, gave an estimated diameter of 74, 92 and 93 kilometers, respectively.
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Because Uranus orbits the Sun almost on its side, and its moons orbit in the planet's equatorial plane, they (including Oberon) are subject to an extreme seasonal cycle. Both northern and southern poles spend 42 years in a complete darkness, and another 42 years in continuous sunlight, with the sun rising close to the zenith over one of the poles at each solstice. The Voyager 2 flyby coincided with the southern hemisphere's 1986 summer solstice, when nearly the entire northern hemisphere was in darkness. Once every 42 years, when Uranus has an equinox and its equatorial plane intersects the Earth, mutual occultations of Uranus's moons become possible.
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The mean diameter of determined from occultations in 2018 is smaller than the larger diameter estimate of by Spitzer in 2008. Despite the large uncertainty in the Spitzer's estimate, the difference of between the two diameters is significant, implying that may have a large satellite with a possible size range of , nearly as large as itself. This possible satellite is expected to orbit at a very close distance of less than , close enough to slow down 's rotation through tidal interactions. If both the primary body and satellite are doubly tidally locked, then the expected orbital period of the satellite would be approximately 54 hours, equal to 's rotaton.
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Under the directorship of Edward Halbach, the MAS joined Operation Moonwatch (aka Project Moonwatch) as another way for the club to make useful scientific contributions. The highlight of the program came in the early morning of September 5, 1962, when members Gale Highsmith, Leonard Schaefer, and Raymond Zit observed the re-entry of Sputnik 4, which allowed the recovery of some of the pieces which fell in and around Manitowoc, Wisconsin. One of 12 "Portascopes" built by the MASIn 1965 the MAS started a program of lunar grazing occultations. Observers were stationed along a 2-mile North-South line at 10th of a mile intervals for the timings.
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24 Scorpii is a star that was originally placed by John Flamsteed within the constellation of Scorpius but in now placed within the southeastern constellation of Ophiuchus. It is visible to the naked eye as a faint, yellow- hued point of light with an apparent visual magnitude of 4.91. Based on the trigonometric parallax published in Gaia Data Release 2, the star lies approximately 121 parsecs or 390 light years away. It is positioned near the ecliptic and thus is subject to lunar occultations. This object is a luminous giant star that is classified by spectral and luminosity class as G7.5II or G7.5II-IIICN1Ba0.5.
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Absolute values of surface pressure are difficult to obtain from occultation data, because this data does not usually reach the lowest layers of the atmosphere. So, surface pressure has to be extrapolated, and this is somewhat ambiguous due to the height dependence of temperature and, consequently, pressure not being completely clear . The radius of Pluto must also be known, but it was poorly constrained before 2015. So, precise values of Pluto's surface pressure were impossible to calculate in previous times. For some occultations since 1988, pressure was calculated for a reference level of from the center of Pluto (which later turned out to be 88±4 km from the surface).
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They can be divided into three groups: nine narrow main rings (6, 5, 4, α, β, η, γ, δ, ε), two dusty rings (1986U2R/ζ, λ) and two outer rings (ν, μ). The rings of Uranus consist mainly of macroscopic particles and little dust, although dust is known to be present in 1986U2R/ζ, η, δ, λ, ν and μ rings. In addition to these well-known rings, there may be numerous optically thin dust bands and faint rings between them. These faint rings and dust bands may exist only temporarily or consist of a number of separate arcs, which are sometimes detected during occultations.
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There have been two reported stellar occultations by Lutetia, observed from Malta in 1997 and Australia in 2003, with only one chord each, roughly agreeing with IRAS measurements. On 10 July 2010, the European Rosetta space probe flew by Lutetia at a minimum distance of km at a velocity of 15 kilometres per second on its way to the comet 67P/Churyumov-Gerasimenko. The flyby provided images of up to 60 meters per pixel resolution and covered about 50% of the surface, mostly in the northern hemisphere. The 462 images were obtained in 21 narrow- and broad-band filters extending from 0.24 to 1 μm.
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Perseid meteor shower. Amateur astronomy is a hobby where participants enjoy observing or imaging celestial objects in the sky using the unaided eye, binoculars, or telescopes. Even though scientific research may not be their primary goal, some amateur astronomers make contributions in doing citizen science, such as by monitoring variable stars, double stars sunspots, or occultations of stars by the Moon or asteroids, or by discovering transient astronomical events, such as comets, galactic novae or supernovae in other galaxies. Amateur astronomers do not use the field of astronomy as their primary source of income or support, and usually have no professional degree in astrophysics or advanced academic training in the subject.
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Nevertheless, flyby occultations can only measure properties along two transects, at their trajectories' entries and exits from Mars' disk as seen from Earth. This results in weather "snapshots" at a particular area, at a particular time. Orbiters then increase the number of radio transects. Later missions, starting with the dual Mariner 6 and 7 flybys, plus the Soviet Mars 2 and 3, carried infrared detectors to measure radiant energy. Mariner 9 was the first to place an infrared radiometer and spectrometer in Mars orbit in 1971, along with its other instruments and radio transmitter. Viking 1 and 2 followed, with not merely Infrared Thermal Mappers (IRTM).
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According to the surveys carried out by the Infrared Astronomical Satellite IRAS, the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), and the Japanese Akari satellite, Simeïsa measures (), () and () kilometers in diameter and its surface has a low albedo of (), () and (), respectively. The Collaborative Asteroid Lightcurve Link assumes an albedo of 0.0376 and derives a diameter of 102.79 kilometers based on an absolute magnitude of 9.12. Alternative mean-diameter measurements published by the WISE team include () and () with corresponding albedos of () and (). Two asteroid occultations on 4 March 1999 and 7 January 2006, gave a best-fit ellipse dimension of () and (), respectively, each with a quality rating of 2.
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According to the surveys carried out by the NEOWISE mission of NASA's Wide- field Infrared Survey Explorer (WISE), the Japanese Akari satellite, and the Infrared Astronomical Satellite IRAS, Tjilaki measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0763 and a diameter of 37.69 kilometers based on an absolute magnitude of 10.53. Alternative mean-diameters published by the WISE team include () and () with a corresponding albedo of () and (). Two asteroid occultations on 20 June 2005 and on 28 July 2009, gave a best-fit ellipse dimension of () and (), respectively, each with an intermediate quality rating of 2.
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Because Uranus orbits the Sun almost on its side, and its moons orbit in the planet's equatorial plane, they (including Umbriel) are subject to an extreme seasonal cycle. Both northern and southern poles spend 42 years in complete darkness, and another 42 years in continuous sunlight, with the Sun rising close to the zenith over one of the poles at each solstice. The Voyager 2 flyby coincided with the southern hemisphere's 1986 summer solstice, when nearly the entire northern hemisphere was unilluminated. Once every 42 years, when Uranus has an equinox and its equatorial plane intersects the Earth, mutual occultations of Uranus's moons become possible.
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He likewise drew up a Blue-book on the climate of "The Isle of Desolation", as Kerguelen was called by Captain Cook. In 1882 he went again with Sidgreaves to observe a similar transit in Madagascar,The Transit of Venus: historical observations - work in progress and he again took advantage of the occasion for magnetic purposes. In 1874 he became a Fellow of the Royal Society. At Stonyhurst College, while he greatly developed the meteorological work of the observatory, and in the province of astronomy made frequent observations of Jupiter's satellites, stellar occultations, comets, and meteors, it was in the department of solar physics that he specially laboured, paying particular attention to sun spots and faculae.
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Jupiter being occulted by the moon, 16 June 2005, in Nelson, New Zealand N.P. Wieth-Knudsen Observatory is next to Tisvilde Hegn, two hours away from Copenhagen, Denmark, at Margot Nyholms vej 19, 3220 Tisvildeleje, on the outskirts of a small residential area in Tisvilde, away from artificial light generated by larger cities. It was constructed in 1959 by Dr. Niels Palle Wieth-Knudsen (1909–1993), who used the observatory until his death. His biggest contribution to astronomy was the observation of lunar occultations, during which the moon passes in front of stars, the data from which is then used in the accurate determination of the lunar position. This became important during the moon landings during the sixties.
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According to the survey carried out by the Infrared Astronomical Satellite IRAS, the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), and the Japanese Akari satellite, Whittemora measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. The Collaborative Asteroid Lightcurve Link adopts the results from IRAS, that is, an albedo of 0.1704 and a diameter of 45.27 km based on an absolute magnitude of 9.26. Further published mean-diameters and albedos by the WISE team include () and () with corresponding albedos of (), and (). Two asteroid occultations on 1 January 2004 and 12 February 2015, gave a best-fit ellipse dimension of 45.0 × 45.0 and 49.0 × 49.0 kilometers, respectively.
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In addition to the 1986U2R/ζ and λ rings, there are other extremely faint dust bands in the Uranian ring system. They are invisible during occultations because they have negligible optical depth, though they are bright in forward-scattered light. Voyager 2's images of forward-scattered light revealed the existence of bright dust bands between the λ and δ rings, between the η and β rings, and between the α ring and ring 4. Many of these bands were detected again in 2003–2004 by the Keck Telescope and during the 2007 ring-plane crossing event in backscattered light, but their precise locations and relative brightnesses were different from during the Voyager observations.
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In 1946 he returned to Cambridge to be based at the Cambridge Observatory as Senior Observer and was able to complete the observational work on his PhD In 1947 he transferred to Dunsink Observatory in Ireland where he stayed until 1953. At Dunsink he produced a number of papers concerning the photoelectric recording of stellar occultations and stellar scintillation , topics that led ultimately to the technologies that support the discovery of exoplanets and the construction of large ground-based optical telescopes respectively. He was also intensely practical and gained a significant reputation for the design and implementation of novel instruments. At Dunsink these skills were put to good effect in building it up as a modern observatory.
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The majority of scientific contributions by amateur astronomers are in the area of data collection. In particular, this applies where large numbers of amateur astronomers with small telescopes are more effective than the relatively small number of large telescopes that are available to professional astronomers. Several organizations, such as the American Association of Variable Star Observers and the British Astronomical Association, exist to help coordinate these contributions. Amateur astronomers often contribute toward activities such as monitoring the changes in brightness of variable stars and supernovae, helping to track asteroids, and observing occultations to determine both the shape of asteroids and the shape of the terrain on the apparent edge of the Moon as seen from Earth.
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From an aesthetic point of view, the inclusion of celestial physics allows the player to experience attractively-rendered sunrises and sunsets while on planet surfaces as well as various satellite occultations. Damocles contains many real-world references, particularly drawn from the UK in the 1980s. For example, the president of the planet Eris is named Margaret, after Margaret Thatcher (British Prime Minister from 1979 to 1990); and there is a bank called Lawson Bank, after Nigel Lawson (British chancellor of the exchequer from 1983 to 1989; though a real Lawson Bank does exist). Some of the references are more elusive; for example, several stores are called "GUM Stores", after the real Russian Gosudarstvennyj Universalnyj Magazin department stores.
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According to the surveys carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), the Japanese Akari satellite, and the Infrared Astronomical Satellite IRAS, Sorga measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. The Collaborative Asteroid Lightcurve Link derives an albedo of 0.1339 and a diameter of 41.70 kilometers based on an absolute magnitude of 9.7. The WISE team also published an alternative mean-diameter of () with an albedo of (). Two asteroid occultations on 24 October 2007, and on 31 October 2012, gave a best-fit ellipse dimension of () and (), with an intermediate and low quality rating of 2 and 1, respectively.
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According to the surveys carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), the Infrared Astronomical Satellite IRAS, and the Japanese Akari satellite, Benda measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. The Collaborative Asteroid Lightcurve Link derives a low albedo of 0.0387 and a diameter of 70.71 kilometers based on an absolute magnitude of 9.9. Alternative mean-diameters published by the WISE team include (), (), (), () and () with a corresponding albedo of (), (), (), () and (). Two asteroid occultations on 4 April 2009 and on 3 September 2013, gave a best-fit ellipse dimension of () and (), respectively, each with a low quality rating of 1.
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Astronomically, the zodiac defines a belt of space extending 9° either side of the ecliptic, within which the orbits of the Moon and the principal planets remain. It is a feature of a celestial coordinate system centered upon the ecliptic, (the plane of the Earth's orbit and the Sun's apparent path), by which celestial longitude is measured in degrees east of the vernal equinox (the ascending intersection of the ecliptic and equator). Stars within the zodiac are subject to occultations by the Moon and other solar system bodies. These events can be useful, for example, to estimate the cross-sectional dimensions of a minor planet, or check a star for a close companion.
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According to the surveys carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), the Infrared Astronomical Satellite IRAS, and the Japanese Akari satellite, Lova measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. The Collaborative Asteroid Lightcurve Link adopts the results from IRAS, that is, a low albedo of 0.0524 and a diameter of 52.47 kilometers based on an absolute magnitude of 10.22. Alternative mean-diameter measurements published by the WISE team include (), (), () and () with corresponding albedos of (), (), () and (). Two asteroid occultations, observed on 5 April 2006 and 12 July 2007, gave a best-fit ellipse dimension of (52.0 × 52.0) and (43.3 × 64.3) kilometers, respectively, with the latter being the better rated one.
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According to the surveys carried out by the Japanese Akari satellite and the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer, Wallia measures between and kilometers in diameter and its surface has an albedo between and . The Infrared Astronomical Satellite IRAS gives a higher albedo of and consequently a smaller diameter of kilometers, while the Collaborative Asteroid Lightcurve Link assumes an albedo of 0.1485 and derives a diameter of based on an absolute magnitude of 9.5. In 2004 and 2012, Wallia was also subject to two asteroid occultations, timed observations when the asteroid passes in front of a distant star. However the measurements were of poor quality in both cases and gave a best-fit ellipse dimension of () and (), respectively.
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The X-rays are probably created by interaction of the gases surrounding Pluto with solar wind, although details of their origin are not clear. Pluto has a tenuous atmosphere consisting of nitrogen (N2), methane (CH4), and carbon monoxide (CO), which are in equilibrium with their ices on Pluto's surface. According to the measurements by New Horizons, the surface pressure is about 1 Pa (10 μbar), roughly one million to 100,000 times less than Earth's atmospheric pressure. It was initially thought that, as Pluto moves away from the Sun, its atmosphere should gradually freeze onto the surface; studies of New Horizons data and ground-based occultations show that Pluto's atmospheric density increases, and that it likely remains gaseous throughout Pluto's orbit.
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A fundamental ephemeris is the basis from which apparent ephemerides, phenomena, and orbital elements are computed for astronomical, nautical, and surveyors' almanacs. Apparent ephemerides give positions and motions of Solar System bodies as seen by observers from the surface of Earth, and are useful for astronomers, navigators, and surveyors in planning observations and in reducing the data acquired, although much of the work of latter two has been supplanted by GPS technology. Phenomena are events related to the configurations of Solar System bodies, for instance rise and set times, phases, eclipses and occultations, and have many civil and scientific applications. Orbital elements are descriptions of the motion of a body at a particular instant, used for further short-time-span calculation of the body's position when high accuracy is not required.
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Fomalhaut b was found to be large and unclearly defined when detected in 2008. This was hypothesized to either be due to a cloud of dust attracted from the dust disc of the star, or a possible ring system, though in 2020 Fomalhaut b itself was determined to be an expanding debris cloud from a collision of asteroids rather than a planet. Similarly, Proxima Centauri c has been observed to be far brighter than expected for its low mass of 7 Earth masses, which may be attributed to a ring system of about 5 . A sequence of occultations of the star 1SWASP J140747.93-394542.6 observed in 2007 over 56 days was interpreted as a transit of a ring system of a (not directly observed) substellar companion dubbed "J1407b".
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Before telegraphy, absolute time could be obtained from astronomical events, such as eclipses, occultations or lunar distances, or by transporting an accurate clock (a chronometer) from one location to the other. The idea of using the telegraph to transmit a time signal for longitude determination was suggested by François Arago to Samuel Morse in 1837, and the first test of this idea was made by Capt. Wilkes of the U.S. Navy in 1844, over Morse's line between Washington and Baltimore. The method was soon in practical use for longitude determination, in particular by the U.S. Coast Survey, and over longer and longer distances as the telegraph network spread across North America and the world, and as technical developments improved accuracy and productivity The "telegraphic longitude net" soon became worldwide.
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All values of ΔT before 1955 depend on observations of the Moon, either via eclipses or occultations. The angular momentum lost by the Earth due to friction induced by the Moon's tidal effect is transferred to the Moon, increasing its angular momentum, which means that its moment arm (approximately its distance from the Earth, i.e. precisely the semi-major axis of the Moon's orbit) is increased (for the time being about +3.8 cm/year), which via Kepler's laws of planetary motion causes the Moon to revolve around the Earth at a slower rate. The cited values of ΔT assume that the lunar acceleration (actually a deceleration, that is a negative acceleration) due to this effect is = −26″/cy2, where is the mean sidereal angular motion of the Moon.
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According to the surveys carried out by the NEOWISE mission of NASA's Wide-field Infrared Survey Explorer (WISE), the Infrared Astronomical Satellite IRAS, and the Japanese Akari satellite, Marghanna measures (), () and () kilometers in diameter and its surface has an albedo of (), () and (), respectively. The Collaborative Asteroid Lightcurve Link derives an albedo of 0.0423 and a diameter of 74.23 kilometers based on an absolute magnitude of 9.7, while the Cornell Mid-IR Asteroid Spectroscopy (MIDAS) survey determined a diameter of () kilometers and Benoit Carry one of () kilometers. Alternative mean- diameters published by the WISE team include (), (), () and () with a corresponding albedo of (), (), () and (). Two asteroid occultations on 11 March 2008 and on 4 May 2010, gave a best-fit ellipse dimension of () and (), respectively, each with an itermediate quality rating of 2.
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Because Ariel, like Uranus, orbits the Sun almost on its side relative to its rotation, its northern and southern hemispheres face either directly towards or directly away from the Sun at the solstices. This means it is subject to an extreme seasonal cycle; just as Earth's poles see permanent night or daylight around the solstices, so Ariel's poles see permanent night or daylight for half a Uranian year (42 Earth years), with the Sun rising close to the zenith over one of the poles at each solstice. The Voyager 2 flyby coincided with the 1986 southern summer solstice, when nearly the entire northern hemisphere was dark. Once every 42 years, when Uranus has an equinox and its equatorial plane intersects the Earth, mutual occultations of Uranus's moons become possible.
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Nicholson received his Ph.D. from Caltech in 1979. Nicholson's research centers on two main areas: orbital dynamics in planetary ring systems and infrared observational studies of planets, their satellites, and their rings. His work has included studies of the ring systems of Saturn, Uranus, and Neptune via Voyager observations and ground-based stellar occultations; Earth-based observations with the 5-meter Hale telescope at Palomar Observatory of several small moons of Jupiter and Saturn discovered by the Voyager spacecraft; dynamical investigations of the planetary system around the pulsar PSR 1257 + 12, and of the rotational evolution of natural satellites; and studies of the zodiacal dust bands discovered by the Infrared Astronomical Satellite in 1983. Together with colleagues in Canada and at Harvard, he has been involved in the discovery of numerous outer satellites of Uranus, Saturn and Neptune.
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Jupiter (the bright object in the upper right) a few minutes before being occulted by the Moon on June 16, 2005 An occultation is an astronomical event where a celestial object appears completely hidden by another, closer body (with a greater angular diameter) due to the passage of the closer object directly between the more distant object and the observer. Due to the large apparent size of the Moon, lunar occultations are quite common and when a bright celestial object is involved, the result is an event that can be easily observed using the naked eye. The Moon almost constantly occults faint stars as it orbits the Earth but because even a young Moon appears immensely brighter than these stars, these events are difficult to observe using amateur telescopes. However, the Moon does frequently occult brighter stars and even planets due to its close proximity to the ecliptic.
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In 1978, the possession of a Catalan grant to promote the research in the university funded her research in spherical astronomy, eclipse, occultations, and transit calculations, stellar systems dynamics and galactic dynamics. Between 1976 and 1979, she worked at the Henri Poincaré Institute because of a program of Spanish-French scientific cooperation and the University of Paris VI. On the other hand, she researched the structure of the Oort cloud at the Observatorie de Meudon. Català had also the opportunity to take part in different financed projects as the one of the European Space Agency which aimed to select and determine the stellar and planetary positions using Hipparcos satellite. Besides her research works, she also studied the Arab science and left works such as Las obras matemáticas de Maslama de Madrid (1965), Arquímedes árabe: el tratado de los círculos tangentes (1968) and Dos tratados del Arquímedes árabe: tratado de los círculos tangentes y el libro de los triángulos (1971).
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Known near-Earth asteroids by size While the size of a small fraction of these asteroids is known to better than 1%, from radar observations, from images of the asteroid surface, or from stellar occultations, the diameter of the vast majority of near Earth asteroids has only been estimated on the basis of their brightness and a representative asteroid surface reflectivity or albedo, which is commonly assumed to be 14%. Such indirect size estimates are uncertain by over a factor of 2 for individual asteroids, since asteroid albedos can range at least as low as 0.05 and as high as 0.3. This makes the volume of those asteroids uncertain by a factor of 8, and their mass by at least as much, since their assumed density also has its own uncertainty. Using this crude method, an absolute magnitude of 17.75 roughly corresponds to a diameter of and an absolute magnitude of 22.0 corresponds to a diameter of .
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Through the mid-20th century, additional mass estimates using this technique would be performed by Marie-Charles Damoiseau, John Couch Adams, Ralph Allen Sampson, and Willem de Sitter, all of which were less than the modern value with the closest being Sampson's 1921 estimate of 4.5 of the mass of Jupiter, which was 4% less than the currently accepted mass. Io's diameter was estimated using micrometer measurements and occultations of background stars by Io. Edward E. Barnard used a micrometer at the Lick Observatory in 1897 to estimate a diameter of , 8.5% larger than the accepted modern value, while Albert A. Michelson, also using the Lick telescope, came up with a better estimate of . The best pre- spacecraft estimate of Io's diameter and shape came from the observations of an occultation of the star Beta Scorpii C on May 14, 1971, where a diameter of was found, slightly less the accepted modern value. These measurements allowed astronomers to estimate Io's density, given as 2.88 g/cm3 following the Beta Scorpii occultation.
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Astronomer Michael R. Molnar argues that the "star in the east" refers to an astronomical event with astrological significance in the context of ancient Greek astrology.Weintraub, David A., "Amazingly, astronomy can explain the biblical Star of Bethlehem", Washington Post, December 26, 2014 He suggests a link between the Star of Bethlehem and a double occultation of Jupiter by the moon on March 20 and April 17 of 6 BC in Aries, particularly the second occultation on April 17..For a similar interpretation, see Minnesota Astronomy Review Volume 18 – Fall 2003/2004 Occultations of planets by the moon are quite common, but Firmicus Maternus, an astrologer to Roman Emperor Constantine, wrote that an occultation of Jupiter in Aries was a sign of the birth of a divine king.. He argues that Aries rather than Pisces was the zodiac symbol for Judea, a fact that would affect previous interpretations of astrological material. Molnar's theory was debated by scientists, theologians, and historians during a colloquium on the Star of Bethlehem at the Netherlands’ University of Groningen in October 2014. Harvard astronomer Owen Gingerich supports Molnar's explanation but noted technical questions.
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New Horizons Commanded into Last Pre-Pluto Slumber JHUAPL August 29, 2014 New Horizons crossed the orbit of Saturn on June 8, 2008, and Uranus on March 18, 2011. After astronomers announced the discovery of two new moons in the Pluto system, Kerberos and Styx, mission planners started contemplating the possibility of the probe running into unseen debris and dust left over from ancient collisions between the moons. A study based on 18 months of computer simulations, Earth-based telescope observations and occultations of the Pluto system revealed that the possibility of a catastrophic collision with debris or dust was less than 0.3% on the probe's scheduled course. If the hazard increased, New Horizons could have used one of two possible contingency plans, the so-called SHBOTs (Safe Haven by Other Trajectories): the probe could have continued on its present trajectory with the antenna facing the incoming particles so the more vital systems would be protected, or, it could have positioned its antenna to make a course correction that would take it just 3000 km from the surface of Pluto where it was expected that the atmospheric drag would have cleaned the surrounding space of possible debris.
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