The name derives from the fairy tale " Goldilocks and the Three Bears", in which a little girl chooses from sets of three items, ignoring the ones that are too extreme (large or small, hot or cold, etc.), and settling on the one in the middle, which is "just right".Ī class of extrasolar planets whose characteristics are similar to Jupiter, but that have high surface temperatures because they orbit very close-between approximately 0.015 and 0.5 AU (2.2 × 10 ^ 6 and 74.8 × 10 ^ 6 km)-to their parent stars, whereas Jupiter orbits its parent star (the Sun) at 5.2 AU (780 × 10 ^ 6 km), causing low surface temperatures.Īn extrasolar planet in an orbit close to its star (normally less than one astronomical unit away), with a mass similar to that of Uranus or Neptune. Two planetary-mass objects orbiting each other.Ī gas giant that orbits its star in an eccentric orbit.Ī planet that does not orbit the Sun, but a different star, a stellar remnant, or a brown dwarf.Ī planet with an orbit that falls within the star's habitable zone. Mini-Neptunes have thick hydrogen–helium atmospheres, probably with deep layers of ice, rock or liquid oceans (made of water, ammonia, a mixture of both, or heavier volatiles).Įither a brown dwarf-an object with a size larger than a planet but smaller than a star-that has formed by processes that typically yield planets-or a sub-brown dwarf, an object smaller than a brown dwarf that does not orbit a star.Īn extrasolar planet with a mass higher than Earth's, but substantially below the mass of the Solar System's smaller gas giants Uranus and Neptune, which are 14.5 and 17.1 Earth masses respectively.Īn astronomical object that's more massive than the planet Jupiter.Ī classification of planets "substantially less massive" than Earth and Venus.Īlso known as a binary planet. A planet up to 10 Earth masses, but less massive than Uranus and Neptune. Assuming "size" is defined by linear dimension (or by volume), mesoplanets should be approximately 1,000 to 5,000 km (620 to 3,110 mi) in diameter.Īlso known as a gas dwarf or transitional planet. A term, not commonly used in the astronomical community, coined by Isaac Asimov. Planets of mass similar to Uranus or Neptune smaller than the gas giants, but still much larger than Earth.Ī planetary body with a size smaller than Mercury, but larger than Ceres. Regardless of their bulk compositions, giant planets normally have thick atmospheres of hydrogen and helium. They are most commonly composed primarily of 'gas' (hydrogen and helium) or 'ices' (volatiles such as water, methane, and ammonia), but may also be composed primarily of rock, which would make one a Mega Earth. Nonetheless, certain planet types have been applied to other planetary-mass objects the Pluto–Charon system has been referred to as " double dwarf planets", for instance.Ī massive planet. Under the IAU definition, true or "major planets" can be distinguished from other planetary-mass objects (PMOs), such as dwarf planets and sub-brown dwarfs. There is currently no accepted definition for exoplanets. The IAU defines that a planet in the Solar System must orbit around the Sun, has enough mass to assume hydrostatic equilibrium, and has " cleared its neighborhood". The following is a list of planet types by their mass, orbit, physical and chemical composition, or by another classification. JSTOR ( February 2020) ( Learn how and when to remove this template message)įrom top to bottom: Mercury, Venus without its atmosphere, Earth and the Moon, Mars, Jupiter, Saturn, Uranus, and Neptune (not to scale).Unsourced material may be challenged and removed.įind sources: "List of planet types" – news Please help improve this article by adding citations to reliable sources. This article needs additional citations for verification.
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