Thankfully, there's another mission on its way to the rocky inner planet called BepiColombo.
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But, this Friday won't be all roses and sonnets — that very same day will see another inner planet hitting reverse.
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According to a newer and competing theory, Phaethon broke off of a larger asteroid, possibly in a collision with an inner planet.
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Similar to the hands on an analog watch, the inner planet shows the hour while the outer planet shows the minutes, all while orbiting around the central axis.
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The Darkness are the reason there are abandoned outposts on just about every inner planet of our solar system, and the only reason we weren't completely wiped out is because the Traveler somehow managed to...fend them off?
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This inner planet requires just 11 hours to make a complete orbit and is located a mere 0.008 au (744,000 miles) from its T-Tauri star (a young, bright star that hasn't quite entered into its main sequence).
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The same measurements also indicated the presence of another inner planet, designated 55 Cancri c.
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It may be in a 4:1 resonance with the inner planet 14 Herculis b.
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Triton, Voyager 2 passed over Neptune's north pole resulting in an acceleration out of the plane of the ecliptic and reduced velocity away from the Sun. A spacecraft traveling from Earth to an inner planet will increase its relative speed because it is falling toward the Sun, and a spacecraft traveling from Earth to an outer planet will decrease its speed because it is leaving the vicinity of the Sun. Although the orbital speed of an inner planet is greater than that of the Earth, a spacecraft traveling to an inner planet, even at the minimum speed needed to reach it, is still accelerated by the Sun's gravity to a speed notably greater than the orbital speed of that destination planet. If the spacecraft's purpose is only to fly by the inner planet, then there is typically no need to slow the spacecraft.
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On March 15, 2017, two planets orbiting LHS 1723 were detected by the HARPS telescope. The inner planet, GJ 3323b, may orbit within the circumstellar habitable zone of its star.
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Announced in June 2008, two extrasolar planets were discovered to be orbiting the star. Both planets are less massive than Jupiter. The inner planet HD 47186 b orbits close to the star and is termed a “hot Neptune”. The outer planet HD 47186 c orbits in a similar distance from the star as the asteroid Vesta, at around 2.4 AU. The inner planet orbits in a circular path while the outer planet orbits in an eccentric path.
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Based upon an 8-year survey using the HARPS spectrograph at La Silla Observatory, in 2011 the detection of a pair of planets orbiting this star were announced. The inner planet, HD 134060 b, is in a tight, eccentric orbit around the star with a period of just over three days. The second object, HD 134060 c, has a more leisurely period of around and a high orbital eccentricity. The star was observed for a few hours by the Spitzer Space Telescope in the hopes of observing a transit by the inner planet, but none was detected.
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The two planets "exchange angular momentum in a 5:1 mean motion resonance". This planet was discovered on the vernal equinox of 2008 by analyzing perturbations with the inner planet HD 17156 b. The paper was submitted to Astrophysical Journal Letters 20 March and revised 14 June.
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On July 26, 2010 the California and Carnegie Planet Search team announced the discovery of two planets around 24 Sextantis along with two planets around HD 200964. The inner planet is twice as massive as Jupiter and takes 453 days to orbit the star in a circular orbit at the average distance of 1.33 AU (199 Gm). The outer planet is 5/6 the mass of Jupiter and takes 883 days to orbit eccentrically around the star at the average distance of 2.08 AU (312 Gm). The two planets are in a 2:1 resonance, meaning that the outer planet orbits the star once every time when the inner planet orbits the star twice.
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On June 3, 2014, the Mars rover Curiosity observed the planet Mercury transiting the Sun, marking the first time a planetary transit has been observed from a celestial body besides Earth. More generally, transits can also occur for Venus and were investigated in the context of searching for the hypothetical inner planet Vulcan.
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It is the first star in Cassiopeia around which an orbiting planet was discovered (in 2007) using the radial velocity method. Later observations showed that this planet also transited the star. In February 2008, a second planet, HD 17156 c, was proposed, with a 5:1 mean motion resonance to the inner planet HD 17156 b.
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As it is typical for very long-period planets, the orbit is eccentric, referring to as "eccentric Jupiter". At periastron, the orbital distance is 3.60 AU and at apastron, the distance is 6.00 AU. The planet's mass is nearly 2 times that of Jupiter, but is likely to be smaller in size than the inner planet.
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In June 2008, the discovery of two extrasolar planets orbiting the star was announced. The planets were discovered using the radial velocity method and the Hobby-Eberly Telescope. The radial velocity data clearly shows the presence of the inner planet (HD 102272 b.) Although there is evidence for another planet, there is insufficient data to unambiguously determine its orbit.
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On July 26, 2010 the California and Carnegie Planet Search team announced the discovery of two planets around HD 200964 along with two planets around 24 Sextantis. The inner planet is nearly twice as massive as Jupiter and takes 614 days to orbit the star in a circular orbit at the average distance of 1.60 AU (240 Gm). The outer planet is 9/10 the mass of Jupiter and takes 825 days to orbit eccentrically around the star at the average distance of 1.95 AU (292 Gm). Due to the close proximity of the two planets to each other the discoverers only found stable orbits near the 4:3 resonance, meaning that every time the outer planet orbits the star three times, the inner planet orbits the star four times.
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The orbital period of the planet outer planet LHS 1140 d was refined to 78 days in 2020. In August 2018, Ment et al., using the transit method of detection, confirmed the existence of the inner planet LHS 1140 c with a mass about 1.8 times Earth's and a radius 1.3 times as large, giving it a density of about 5 g/cm3.
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The star is reported to be orbited by the super-Earth extrasolar planets CoRoT-7b and CoRoT-7c, both discovered in 2009. The existence of a possible third planet CoRoT-7d, detected in a published study, remains unconfirmed. The discovery of the inner planet was made using the astronomical transit method by the CoRoT program. CoRoT-7b is notable for its small size.
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The orbital elements of this planet were refined in 2018, showing an orbital period of , a semimajor axis of , and an eccentricity of 0.16. The minimum mass of this object is nearly double that of Jupiter. If an inner planet is orbiting the star, it must have an orbital period no greater than to satisfy Hill's criteria for dynamic stability.
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Interior planet now seems to be the preferred term for astronomers. Inferior/interior and superior are different from the terms inner planet and outer planet, which designate those planets which lie inside the asteroid belt and those that lie outside it, respectively. Inferior planet is also different from minor planet or dwarf planet. Superior planet is also different from gas giant.
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Announced in 2009, two extrasolar planets were discovered to be orbiting the star. Both planets are less massive than Jupiter. The inner planet HD 215497 b orbits very close to the star and is termed a “hot super-Earth”. The outer planet HD 215497 c is Saturn-sized and orbits a little bit further from the star as the Earth, at around 1.282 AU.
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On the other hand, an observer on Mars would see the Moon rotate, with the same period as its orbital period, and would see far side features that can never be seen from Earth. Since Earth is an inner planet, observers on Mars can occasionally view transits of Earth across the Sun. The next one will take place in 2084. They can also view transits of Mercury and transits of Venus.
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In 1998 a planet was discovered orbiting 14 Herculis. The planet's eccentric orbital period is 4.8 years. In 2005, a possible second planet was proposed, designated 14 Herculis c. The parameters of this planet are uncertain, but a recent analysis suggests it may lie in the 4:1 resonance with the inner planet, with an orbital period of almost 19 years at an orbital distance of 6.9 AU.
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Charles Gramlich, The Greenwood Encyclopedia of Science Fiction and Fantasy: Themes, Works, and Wonders, pp. 1209-1211 Burroughs followed up this first book with several more Barsoom stories, and another series that could be considered Sword & Planet, featuring as hero Carson Napier and his adventures on Venus, natively known as Amtor. Burroughs' Pellucidar series could arguably be considered sword- and-(inner) planet, as it follows most of the plot conventions described below.
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The Moon is similar, but lacks a substantial iron core. Three of the four solar terrestrial planets (Venus, Earth, and Mars) have substantial atmospheres; all have impact craters and tectonic surface features such as rift valleys and volcanoes. The term inner planet should not be confused with inferior planet, which refers to any planet that is closer to the Sun than the observer's planet is, but usually refers to Mercury and Venus.
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HD 45364 is one of only a relative few systems that have had more than one exoplanet discovered in its orbit. The two planets, HD 45364 b and HD 45364 c respectively, were both discovered in August 2008 using the radial velocity method. The pair are orbiting the host star with a 3:2 mean motion resonance, which means the inner planet is completing three orbits for every two orbits of the outer planet.
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As of 2009, HAT-P-13 has been confirmed to have two extrasolar planets orbiting it. The inner planet was discovered by the "transit method" and the outer planet was found through the radial velocity method. A search for transits by HAT-P-13c was negative, however only 72% of the possible transit configurations could be ruled out. HAT-P-13 was the first star to have a transiting planet and an additional planet on a known orbit.
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Preliminary astrometric measurements suggest the orbit of Upsilon Andromedae d may be inclined at 155.5° to the plane of the sky. However, these measurements were later proved useful only for upper limits; , and contradict even the inner planet u And b's inclination of >30°. The mutual inclination between c and d meanwhile is 29.9 degrees. The true inclination of Upsilon Andromedae d was determined as 23.8° after combined results were measured from the Hubble Space Telescope and radial velocity measurements.
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According to Nelson & Angel (1998), Eta Cephei would show two significant periodicities of 164 days and 10 years respectively, hinting at the possible presence of one or more jovian planets in orbit around the subgiant. The authors have set an upper limit of 0.64 Jupiter masses for the putative inner planet and 1.2 Jupiter masses for the putative outer one. Also Campbell et al. (1988) inferred the existence of planetary objects or even brown dwarfs less massive than 16.3 Jupiter masses.
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The orbits of the planets of Gliese 876. Gliese 876 b is the third planet from the star. Gliese 876 b is in a 1:2:4 Laplace resonance with the inner planet Gliese 876 c and the outer planet Gliese 876 e: in the time it takes planet e to complete one orbit, planet b completes two and planet c completes four. This is the second known example of a Laplace resonance, the first being Jupiter's moons Io, Europa and Ganymede.
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By making sensitive measurements of the Doppler shift of the spectrum of 55 Cancri A, a 15-day periodicity was detected. The planet was announced in 1996, together with the planet of Tau Boötis and the innermost planet of Upsilon Andromedae. Even when this inner planet, with a mass at least 78% times that of Jupiter was accounted for, the star still showed a drift in its radial velocity. This eventually led to the discovery of the outer planet 55 Cancri d in 2002.
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In this case, it may be a candidate for the parent body of the mesosiderites, a class of stony–iron meteorites. Another possibility is that Psyche may be an endmember of diverse relic bodies left by the inner planet formation. The asteroid's mantle may have been stripped away not by a single collision but by multiple ( > 3 ) relatively slow side-swipe collisions with bodies of comparable or larger size. What is left is a metallic core covered by a thin layer of silicates, which reveals itself spectrally.
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At the time, the parameters of this planet were poorly constrained and it was thought to be in an orbit of around 8.2 years with a high eccentricity. Later in 2004, a small inner planet designated Mu Arae c was announced with a mass comparable to that of Uranus in a 9-day orbit. This was the first of the class of planets known as "hot Neptunes" to be discovered. The discovery was made by making high-precision radial velocity measurements with the High Accuracy Radial Velocity Planet Searcher (HARPS) spectrograph.
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The presence of giants tends to increase eccentricities and inclinations (see Kozai mechanism) of planetesimals and embryos in the terrestrial planet region (inside 4 AU in the Solar System). If giant planets form too early, they can slow or prevent inner planet accretion. If they form near the end of the oligarchic stage, as is thought to have happened in the Solar System, they will influence the merges of planetary embryos, making them more violent. As a result, the number of terrestrial planets will decrease and they will be more massive.
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All of the planets are too close to their star to be considered within the habitable zone. Although Kepler-138c and d have the same size, their masses and densities vary greatly. Of these two, the inner planet is consistent with a rocky super-Earth, whereas the outer planet's low density implies it may have a substantial proportion of water ice or a significant gas envelope, resembling a miniaturized gas giant (a Gas dwarf). The striking differences between these two planets have been hypothesized to be due photoevaporation.
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There is also a linear trend in the radial velocities, which may indicate an additional outer planet. The best two-planet model gives a different period and mass for the inner planet (9.8 years and 3.4 Jupiter masses), with an outer planet of 2.1 Jupiter masses in a 37-year orbit. However the two-planet model does not represent a significant improvement over the model with one planet and a linear trend, so more observations are needed to constrain the parameters of the outer planet. Rickman et al.
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In 1997, the discovery of a 51 Pegasi-like planet orbiting 55 Cancri A was announced, together with the planet of Tau Boötis and the inner planet of Upsilon Andromedae. The planet was discovered by measuring the star's radial velocity, which showed a periodicity of around 14.7 days corresponding to a planet at least 78% of the mass of Jupiter. These radial velocity measurements still showed a drift unaccounted-for by this planet, which could be explained by the gravitational influence of a more distant object. In 1998 the discovery of a possible dust disk around 55 Cancri A was announced.
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On September 12, 2011 three low-mass planets were announced using data from the HARPS spectrograph. These three planets are among about seven dozen planets discovered in September 2011, the most of any month during the exoplanet era that begun in early 1990s. The two inner planet were also found using a transit method in 2020, allowing a precise determination of their mass and radii. With a minimum mass of about 5 Earth masses, the innermost planet falls into the regime of Super-Earths, and was confirmed to be mostly rocky with density 7.8 g/cm3 in 2020.
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The Alinda asteroids are a dynamical group of asteroids with a semi-major axis of about 2.5 AU and an orbital eccentricity approximately between 0.4 and 0.65.Minor planet groups/families The namesake is 887 Alinda, discovered by Max Wolf in 1918. These objects are held in this region by the 1:3 orbital resonance with Jupiter, which results in their being close to a 4:1 resonance with Earth. An object in this resonance has its orbital eccentricity steadily increased by gravitational interactions with Jupiter until it eventually has a close encounter with an inner planet that breaks the resonance.
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The European ExoMars Trace Gas Orbiter is currently measuring and mapping the atmospheric methane. ;Planetary systems It is possible that some exoplanets may have moons with solid surfaces or liquid oceans that are hospitable. Most of the planets so far discovered outside the Solar System are hot gas giants thought to be inhospitable to life, so it is not yet known whether the Solar System, with a warm, rocky, metal-rich inner planet such as Earth, is of an aberrant composition. Improved detection methods and increased observation time will undoubtedly discover more planetary systems, and possibly some more like ours.
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Orbiting the star are three planets, whose discovery was announced in 2008; the discovery paper was published in 2009. The inner planet has a mass at least 7.5 times that of Earth, and is termed a super-Earth (this classification is based solely on the mass of the planet and should not be taken to imply that the planet could support Earthlike conditions). The middle planet and the outer planet are gas giants. The orbital periods for three planets are 9.3743 days for a 7.56 ME planet, 962 days for a 0.64 MJ planet, and 2172 days for a 0.54 MJ planet.
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Even when both of the two planets were accounted for, there was still a periodicity at around 43 days. However, this period is close to the rotation period of 55 Cancri A, which led to the possibility that the 43-day period was caused by stellar rotation rather than a planet. Both the 43-day planet (designated 55 Cancri c) and the 5 AU planet (designated 55 Cancri d) were announced in the same paper, labeled in order of increasing distance from the star. Further measurements which led to the discovery of the inner planet 55 Cancri e in 2004 lent support to the planet hypothesis.
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Planetesimals can be removed from the planet's influence after encountering an adjacent planet or transferred to that planet's influence. These interactions cause the planet's orbits to diverge as the outer planet tends to remove planetesimals with larger momentum from the inner planet influence or add planetesimals with lower angular momentum, and vice versa. The planet's resonances, where the eccentricities of planetesimals are pumped up until they intersect with the planet, also act as a source. Finally, the planet's migration acts as both a sink and a source of new planetesimals creating a positive feedback that tends to continue its migration in the original direction.
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Oort noted that the number of returning comets was far less than his model predicted, and this issue, known as "cometary fading", has yet to be resolved. No dynamical process are known to explain the smaller number of observed comets than Oort estimated. Hypotheses for this discrepancy include the destruction of comets due to tidal stresses, impact or heating; the loss of all volatiles, rendering some comets invisible, or the formation of a non-volatile crust on the surface. Dynamical studies of hypothetical Oort cloud comets have estimated that their occurrence in the outer-planet region would be several times higher than in the inner-planet region.
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In the 5-planet solution for the 55 Cancri system, the orbit of 55 Cancri c is mildly eccentric: at apoastron the planet is about 19% further from the star than it is at periastron. It is located closer to 55 Cancri A than Mercury is to our sun, though it has a longer orbital period than the hot Jupiters. The planet is located close to a 3:1 resonance with the inner planet 55 Cancri b; however, simulations indicate that the two planets are not actually in this resonance. A limitation of the radial velocity method used to discover the planet is that only a lower limit on the mass can be obtained.
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In 2008, a second planet, designated "Gliese 436 c" was claimed to have been discovered, with an orbital period of 5.2 days and an orbital semimajor axis of 0.045 AU. The planet was thought to have a mass of roughly 5 Earth masses and have a radius about 1.5 times larger than the Earth's. Due to its size, the planet was thought to be a rocky, terrestrial planet. It was announced by Spanish scientists in April 2008 by analyzing its influence on the orbit of Gliese 436 b.Reuters Further analysis showed that the transit length of the inner planet is not changing, a situation which rules out most possible configurations for this system.
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Upsilon Andromedae c was detected by measuring variations in its star's radial velocity as a result of the planet's gravity. This was done by making precise measurements of the Doppler shift of the spectrum of Upsilon Andromedae A. At the time of discovery, Upsilon Andromedae A was already known to host one extrasolar planet, the hot Jupiter Upsilon Andromedae b, however by 1999 it was clear that the inner planet could not explain the velocity curve. In 1999, astronomers at both San Francisco State University and the Harvard-Smithsonian Center for Astrophysics independently concluded that a three-planet model best fit the data. The two new planets were designated Upsilon Andromedae c and Upsilon Andromedae d.
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Upsilon Andromedae d was detected by measuring variations in its star's radial velocity as a result of the planet's gravity. This was done by making precise measurements of the Doppler shift of the spectrum of Upsilon Andromedae A. At the time of discovery, Upsilon Andromedae A was already known to host one extrasolar planet, the hot Jupiter Upsilon Andromedae b; however, by 1999, it was clear that the inner planet could not explain the velocity curve. In 1999, astronomers at both San Francisco State University and the Harvard-Smithsonian Center for Astrophysics independently concluded that a three-planet model best fit the data. The two new planets were designated Upsilon Andromedae c and Upsilon Andromedae d.
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The migration of planets can lead to planets being captured in resonances and chains of resonances if their orbits converge. The orbits of the planets can converge if the migration of the inner planet is halted at the inner edge of the gas disk, resulting in a systems of tightly orbiting inner planets; or if migration is halted in a convergence zone where the torques driving Type I migration cancel, for example near the ice line, in a chain of more distant planets. Gravitational encounters can also lead to the capture of planets with sizable eccentricities in resonances. In the Grand tack hypothesis the migration of Jupiter is halted and reversed when it captured Saturn in an outer resonance.
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Earth and the Moon as viewed from Mars (MRO; HiRISE; November 20, 2016) As seen from Mars, the Earth is an inner planet like Venus (a "morning star" or "evening star"). The Earth and Moon appear starlike to the naked eye, but observers with telescopes would see them as crescents, with some detail visible. An observer on Mars would be able to see the Moon orbiting around the Earth, and this would easily be visible to the naked eye. By contrast, observers on Earth cannot see any other planet's satellites with the naked eye, and it was not until soon after the invention of the telescope that the first such satellites were discovered (Jupiter's Galilean moons).
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In March 2017, two candidate planets were discovered orbiting Luyten's Star. The outer planet, GJ 273b, is a Super Earth in its star's habitable zone. It has a mass of 2.89 ± 0.26 Earth masses and orbits at a distance of 0.09110 ± 0.00002 AU, completing one orbital period in 18.650 ± 0.006 days. While the planet is on the innermost edge of the star's conservative habitable zone, the incident flux is only 1.06S⊕, so it may be potentially habitable if water and an atmosphere are present; depending on albedo, its equilibrium temperature could be anywhere between 206 and 293 Kelvin. The inner planet, GJ 273c, is one of the lightest exoplanets detected by radial velocities, with a mass of only 1.18 ± 0.16 Earth masses.
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However, if the spacecraft is to be inserted into orbit about that inner planet, then there must be some way to slow it down. Similarly, while the orbital speed of an outer planet is less than that of the Earth, a spacecraft leaving the Earth at the minimum speed needed to travel to some outer planet is slowed by the Sun's gravity to a speed far less than the orbital speed of that outer planet. Therefore, there must be some way to accelerate the spacecraft when it reaches that outer planet if it is to enter orbit about it. However, if the spacecraft is accelerated to more than the minimum required, less total propellant will be needed to enter orbit about the target planet.
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The orbital period of Gliese 581d was originally thought to be 83 days but was later revised to a lower value of 67 days. The revised orbital distance would place it at the outer limits of the habitable zone, the distance at which it is believed possible for liquid water to exist on the surface of a planetary body, given favourable atmospheric conditions. Gliese 581d was estimated to receive about 30% of the intensity of light the Earth receives from the Sun. By comparison, sunlight on Mars has about 40% of the intensity of that on Earth, though if high levels of carbon dioxide are present in the planetary atmosphere, the greenhouse effect could keep temperatures above freezing. The next discovery was the inner planet Gliese 581e, also by the Observatory of Geneva and using data from the HARPS instrument, was announced on 21 April 2009.
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