"Neptune Neptune is the eighth and farthest known planet from the Sun in the Solar System. In the Solar System, it is the fourth-largest planet by diameter, the third-most-massive planet, and the densest giant planet. Neptune is 17 times the mass of Earth and is slightly more massive than its near-twin Uranus, which is 15 times the mass of Earth and slightly larger than Neptune. Neptune orbits the Sun once every 164.8 years at an average distance of . It is named after the Roman god of the sea and has the astronomical symbol ♆, a stylised version of the"
"25, 2011 discovery, the densest planet ever discovered, at nearly 20 times the density of Jupiter (about 23 times the density of water). It is slightly more massive than Jupiter. It is thought to be composed of oxygen and carbon (as opposed to hydrogen and helium, the main components of gas giants like Jupiter and Saturn). The oxygen is most likely on the surface of the planet, with increasingly higher quantities of carbon deeper inside the planet. The intense pressure acting upon the planet suggests that the carbon is crystallized, much like diamond is. PSR J1719-1438 b orbits its host"
"as well as composition. The uncompressed density of terrestrial planets trends towards lower values as the distance from the Sun increases. The rocky minor planet Vesta orbiting outside of Mars is less dense than Mars still at, 3.4 g·cm. Calculations to estimate uncompressed density inherently require a model of the planet's structure. Where there have been landers or multiple orbiting spacecraft, these models are constrained by seismological data and also moment of inertia data derived from the spacecraft orbits. Where such data is not available, uncertainties are inevitably higher. It is unknown, whether extrasolar terrestrial planets in general will show"
"its close distance the system is considered an excellent target for studying atmospherics of exoplanets. In late 2017, the masses of all three planets were determined using the Planet Finder Spectrograph on the Magellan II Telescope. Planet b was found to be very iron-rich, planet c appears to be mainly rocky, and planet d is a typical volatile-rich planet. GJ 9827b is noted as being one of the densest planets yet found, with its mass containing about ≥50% iron. More precise radial velocity measurements released in late February 2018 revealed that all three planets have a lower density than Earth"
"determine the mass, density, and gravity of the planet. TRAPPIST-1c is the third-largest planet of the TRAPPIST-1 system, with a radius of 1.095 . It is also the most massive of the system as well, with a mass of 1.156 , slightly higher than that of the next most massive, TRAPPIST-1g. Despite its Earth-like mass and radius, TRAPPIST-1c has a lower density (4.89 g/cm) and gravity (0.966g) than Earth. This is consistent with a rock-based composition and a thick, Venus-like atmosphere of water vapor, similar to TRAPPIST-1b. TRAPPIST-1c's atmosphere is expected to be thinner than that of its inner sibling,"
"the poles and is lower than the surface gravity of Earth. However, the equatorial escape velocity of nearly is much higher than that for Earth. Saturn is the only planet of the Solar System that is less dense than water—about 30% less. Although Saturn's core is considerably denser than water, the average specific density of the planet is due to the atmosphere. Jupiter has 318 times Earth's mass, and Saturn is 95 times Earth's mass. Together, Jupiter and Saturn hold 92% of the total planetary mass in the Solar System. Despite consisting mostly of hydrogen and helium, most of Saturn's"
"massive and dense planet could be Kepler-131b, although its density is not as well measured as that of Kepler 10c. The next most massive known solid planets are half this mass: 55 Cancri e and Kepler-20b. Gas planets can have large solid cores. The Saturn-mass planet HD 149026 b has only two-thirds of Saturn's radius, so it may have a rock–ice core of 60 Earth masses or more. Corot-20b has 4.24 times Jupiter's mass but a radius of only 0.84 that of Jupiter; it may have a metal core of 800 Earth masses if the heavy elements are concentrated in"
"density is the second highest in the Solar System at 5.427 g/cm, only slightly less than Earth's density of 5.515 g/cm. If the effect of gravitational compression were to be factored out from both planets, the materials of which Mercury is made would be denser than those of Earth, with an uncompressed density of 5.3 g/cm versus Earth's 4.4 g/cm. Mercury's density can be used to infer details of its inner structure. Although Earth's high density results appreciably from gravitational compression, particularly at the core, Mercury is much smaller and its inner regions are not as compressed. Therefore, for it"
"1.87 and 2.52 g·cm, respectively, and Haumea's density is similar to Pallas's 2.8 g·cm). The Earth's Moon has a density of 3.4 g·cm and Jupiter's satellites, Io, 3.528 and Europa, 3.013 g·cm; other satellites typically have densities less than 2 g·cm. The uncompressed density of a terrestrial planet is the average density its materials would have at zero pressure. A greater uncompressed density indicates greater metal content. Uncompressed density differs from the true average density (also often called ""bulk"" density) because compression within planet cores increases their density; the average density depends on planet size, temperature distribution and material stiffness"
"or with a larger surface covered with liquid water, could be more hospitable for life than Earth. Since the volume of a planet tends to be directly related to its mass, the more massive it is, the greater its gravitational pull, which can result in a denser atmosphere. Some studies indicate that there is a natural limit, set at 1.6R, below which nearly all planets are terrestrial, composed primarily of rock-iron-water mixtures. Generally, objects with a mass below 6 M are very likely to be of similar composition as Earth. Above this limit, the density of the planets decreases with"
"LHS 1140 b LHS 1140 b is a massive, dense rocky planet orbiting within the conservative habitable zone of the red dwarf LHS 1140. Discovered in 2017 by the MEarth Project, LHS 1140 b is nearly 7 times the mass of Earth and over 40% larger in radius, putting it within the Super-Earth category of planets. It is one of the densest planets found, with a density over twice that of Earth, along with a high surface gravity of about 3.25g. LHS 1140 b orbits entirely within the star's habitable zone and gets 41% the incident flux of Earth. The"
"accurately determined. The planets range in mass from about 0.3 to 1.16 , with densities from 0.62 ""ρ"" (3.4 g/cm) to 1.02 ""ρ"" (5.6 g/cm). Planets c and e are almost entirely rocky, while b, d, f, g, and h have a layer of volatiles in the form of either a water shell, an ice shell, or a thick atmosphere. TRAPPIST-1d appears to have a liquid water ocean comprising about 5% of its mass—for comparison, Earth's water content is —while the water layers of TRAPPIST-1f and g are likely frozen. TRAPPIST-1e has a slightly higher density than Earth, indicating a"
"than Jupiter can be larger, so-called ""puffy planets"" (gas giants with a large diameter but low density). An example of this may be the exoplanet HAT-P-1b with about half the mass of Jupiter but about 1.38 times larger diameter. Corot-3b, with a mass around 22 Jupiter masses, is predicted to have an average density of 26.4 g/cm, greater than osmium (22.6 g/cm), the densest natural element under standard conditions. Extreme compression of matter inside it causes the high density, because it is likely composed mainly of hydrogen. The surface gravity is also high, over 50 times that of Earth. In"
"appears to the human eye, is 11.39. Therefore, it is far too dim to be seen without a telescope. K2-38b K2-38b, also designated EPIC 204221263 b, is a massive rocky exoplanet closely orbiting a Sun-like star and is one of the densest planets ever found. Discovered in 2016 by Crossfield et al. and later characterized by Sinukoff et al., K2-38b is a rocky Super-Earth about 55% larger than Earth but about 12 times more massive, indicating a composition rich in iron and an extremely high surface gravity. The planet is within K2 Campaign 2, in the constellation Scorpius. K2-38b is"
"uniform density, formula_1. For a differentiated planet or satellite, where there is an increase of density with depth, formula_2. The quantity is a useful indicator of the presence and extent of a planetary core, because a greater departure from the uniform-density value of 0.4 conveys a greater degree of concentration of dense materials towards the center. The Sun has by far the lowest moment of inertia factor value among Solar System bodies; it has by far the highest central density (, compared to ~13 for Earth) and a relatively low average density (1.41 g/cm versus 5.5 for Earth). Saturn has"
"HARPS spectrograph revealed that K2-229b was far denser and more massive than initially expected. The planet has a mass of 2.59 and an extremely high density of about 8.9 g/cm, giving it about 91% more surface gravity than Earth. The unusually high mass and density of K2-229b indicates a Mercury-like composition dominated by an iron core taking up about 70% of the planet's mass. Due to its extremely tight orbit, K2-229b is one of the hottest planets yet found. It has an equilibrium temperature of , hot enough to melt iron. The day side has an even higher temperature in"
"southern constellation of Centaurus. , the least massive planet known is PSR B1257+12 A, which is about twice the mass of the Moon. The most massive planet listed on the NASA Exoplanet Archive is DENIS-P J082303.1-491201 b, about 29 times the mass of Jupiter, although according to most definitions of a planet, it is too massive to be a planet and may be a brown dwarf instead. Almost all of the planets detected so far are within the Milky Way, but there have also been a few possible detections of extragalactic planets. The study of planetary habitability also considers a"
"between 1.75 and 1.83 Earth radii), the mass is not as well constrained, with a range between 0.9 and 3.3 Earth masses. The mass is determined using transit timing variations of Kepler-11c, and is limited by the quality of the data. Kepler-11b is the closest planet to its host star in the Kepler-11 planetary system. With an estimated density of 1.7 g/cm, comparable to Neptune's, Kepler-11b is denser than the solar system's gas giants but significantly less dense than the terrestrial planets. The estimated density range suggests that it is not of Earth-like composition, yet it is nonetheless composed mostly"
"Earth, Kepler-8 is an extremely dim star. It cannot be seen with the naked eye. Kepler-8b is the only planet that has been discovered in the orbit of Kepler-8. With a mass of .603 M and a radius of 1.419 R, the planet is 60% the mass of, but 42% larger than planet Jupiter. The planet is diffuse, with a density of .261 grams/cc, especially in comparison to Jupiter and its density of 5.515 grams/cc. At a distance of .0483 AU, Kepler-8b orbits its star every 3.5225 days. The eccentricity of Kepler-8 is assumed to be 0, which would give"
"or a mini-Neptune with a hydrogen–helium atmosphere. Another possibility for a low-mass low-density planet is that it has a large atmosphere made up chiefly of carbon monoxide, carbon dioxide, methane, or nitrogen. In 2014, new measurements of Kepler-10c found it to be a Neptune-mass planet (17 Earth masses) with a density higher than Earth's, indicating that Kepler-10c is composed mostly of rock with possibly up to 20% high-pressure water ice but without a hydrogen-dominated envelope. Because this is well above the 10-Earth-mass upper limit that is commonly used for the term 'super-Earth', the term mega-Earth has been coined. A similarly"
"that their mean density decreases with distance from Jupiter. Callisto, the outermost and least dense of the four, has a density intermediate between ice and rock whereas Io, the innermost and densest moon, has a density intermediate between rock and iron. Callisto has an ancient, heavily cratered and unaltered ice surface and the way it rotates indicates that its density is equally distributed, suggesting that it has no rocky or metallic core but consists of a homogeneous mix of rock and ice. This may well have been the original structure of all the moons. The rotation of the three inner"
"of Jupiter but due to proximity to its star the planet has expanded to a radius of 1.478 that of Jupiter. Because of this its mean density is only 0.166 g/cm, about the same as expanded polystyrene, a substance used to manufacture lightweight, disposable commercial plastic products. Only WASP-17b (0.49""M""; 1.66""R"") was known to have a lower density at the time of Kepler-7b's discovery. Such low densities are not predicted by current standard theories of planet formation. Kepler-7b orbits its host star every 4.8855 days at a distance of , making it the furthest-orbiting planet of the first five discovered"
"naked eye. The binary system is known to host three planets, all larger than Earth with no solid surface. The innermost planet, Kepler-47b, is a gas giant and resides close to its parent stars and therefore is inhospitable to life. It is thought to be smaller than Kepler-47c and is roughly three times the radius of Earth. The second planet, Kepler-47c, is also a gas giant and the outermost planet. It is situated within the habitable zone and its radius is 4 times the Earth's. Although it is assumed Kepler-47c is not capable of harboring life, it is marginally larger"
"density, is one of the largest known solid objects in the Solar System that is less dense than water. Why this should be is not well understood, because objects of its size in the Kuiper belt often contain a fair amount of rock and are hence pretty dense. To have a similar composition to others large KBOs, it would have to be exceptionally porous, which is unlikely given the compactability of water ice. Hence, its density astonished astronomers. The discovery of a minor-planet moon was reported in IAUC 8812 on 22 February 2007. The satellite was detected using the Hubble"
"Uranus or Neptune. However, the high density of 9.9 g/cm^3 indicates a rocky composition not too different from Earth's albeit with more iron. Without a rocky surface, life may never be able to develop on a planet. Kepler-1652b has a calculated mass of about 7 times that of Earth, which could help power a strong magnetic field. Red dwarfs like Kepler-1652 can produce very strong flares, much more powerful than what the Sun produces, which could erode away the atmosphere of orbiting planets, compromising their habitability. While not all red dwarfs are this active, a strong magnetic field can still"
"also give a mass of around 0.086 ± 0.084 M. These two values make TRAPPIST-1h the smallest of all the planets in its system. The planet's density is around 1.297 ± 1.266 g/cm, and its gravity is only around 0.168 times that of Earth, similar to the gravitational pull of the Moon. It has an equilibrium temperature of , similar to that of Earth's south pole. The planet orbits an (M-type) ultracool dwarf star named TRAPPIST-1. The star has a mass of 0.08 ""M"" and a radius of 0.11 ""R"". It has a temperature of 2550 K and is between"
"with a higher density than Earth (TRAPPIST-1c also appears to be just about entirely rock, but it has an extremely thick atmosphere that makes it less dense than TRAPPIST-1e). It has a density of 5.65 g/cm, about 1.024 times Earth's density of 5.51 g/cm. The higher density of TRAPPIST-1e implies a very Earth-like composition and a solid rocky surface. This is also unusual among the TRAPPIST-1 planets, as most are completely covered in either a thick steam atmosphere, a global liquid ocean, or an ice shell. TRAPPIST-1e has 93% the surface gravity of Earth, the second highest in the system."
"than 2 Earth radii) and in the habitable zone of their star. Since then, Kepler has discovered hundreds of planets ranging from Moon-sized to super-Earths, with many more candidates in this size range (see image). The following exoplanets have a density of at least 5 g/cm and a mass below Neptune's and are thus very likely terrestrial: Kepler-10b, Kepler-20b, Kepler-36b, Kepler-48d, Kepler 68c, Kepler-78b, Kepler-89b, Kepler-93b, Kepler-97b, Kepler-99b, Kepler-100b, Kepler-101c, Kepler-102b, Kepler-102d, Kepler-113b, Kepler-131b, Kepler-131c, Kepler-138c, Kepler-406b, Kepler-406c, Kepler-409b. The Neptune-mass planet Kepler-10c also has a density >5 g/cm and is thus very likely terrestrial. In 2013, astronomers reported, based"
"the Moon causes ocean tides, stabilizes Earth's orientation on its axis, and gradually slows its rotation. Earth is the densest planet in the Solar System and the largest of the four terrestrial planets. Earth's lithosphere is divided into several rigid tectonic plates that migrate across the surface over periods of many millions of years. About 71% of Earth's surface is covered with water, mostly by oceans. The remaining 29% is land consisting of continents and islands that together have many lakes, rivers and other sources of water that contribute to the hydrosphere. The majority of Earth's polar regions are covered"
"to oxygen may be orbited by planets that are mostly carbides, with the most common material being silicon carbide. This has a higher thermal conductivity and a lower thermal expansivity than silicates. This would result in more rapid conductive cooling near the surface, but lower down the convection could be at least as vigorous as that in silicate planets. One such planet is PSR J1719-1438 b, companion to a millisecond pulsar. It has a density at least twice that of lead, and may be composed mainly of ultra-dense diamond. It is believed to be the remnant of a white dwarf"
"noteworthy that the Earth has the highest density of all the planets in the Solar system; the absorption of the core of the impactor body explains this observation, given the proposed properties of the early Earth and Theia. Comparison of the zinc isotopic composition of Lunar samples with that of Earth and Mars rocks provides further evidence for the impact hypothesis. Zinc is strongly fractionated when volatilized in planetary rocks, but not during normal igneous processes, so zinc abundance and isotopic composition can distinguish the two geological processes. Moon rocks contain more heavy isotopes of zinc, and overall less zinc,"
"mostly between the size of Neptune and the size of Earth. If a planet is detectable by both the radial-velocity and the transit methods, then both its true mass and its radius can be determined, as well as its density. Planets with low density are inferred to be composed mainly of hydrogen and helium, whereas planets of intermediate density are inferred to have water as a major constituent. A planet of high density is inferred to be rocky, like Earth and the other terrestrial planets of the Solar System. Gaseous planets that are hot is because they are close to"
"results from polarimetric studies indicate that the planet has predominately blue color, is 1.36 times as large and 0.74 times as massive as Jupiter, meaning that the mean density is 0.36g/cm. It has a geometric albedo of 0.35 in visible light. Tidal heating models predict a similar mass for the planet. Upsilon Andromedae b appears to be responsible for increased chromospheric activity on its parent star. Observations suggest that there is a ""hot spot"" on the star around 169° away from the sub-planetary point. This may be the result of interactions between the magnetic fields of the planet and the"