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The following is a list of planet types by their mass, orbit, physical and chemical composition, or by another classification. 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 structure of rocky planets is constrained by the average density of a planet and its moment of inertia. [15] The moment of inertia for a differentiated planet is less than 0.4, because the density of the planet is concentrated in the center. [16] Mercury has a moment of inertia of 0.346, which is evidence for a core. [17]
Terrestrial planets are substantially different from the giant planets, which might not have solid surfaces and are composed mostly of some combination of hydrogen, helium, and water existing in various physical states. Terrestrial planets have a compact, rocky surfaces, and Venus, Earth, and Mars each also has an atmosphere. Their size, radius ...
The radius and composition of all these planets are unknown. Sizes of Kepler planet candidates based on 2,740 candidates orbiting 2,036 stars as of 4 November 2013 ( NASA ) The first confirmed terrestrial exoplanet , Kepler-10b , was found in 2011 by the Kepler space telescope , specifically designed to discover Earth-size planets around other ...
The eight planets of the Solar System with size to scale (up to down, left to right): Saturn, Jupiter, Uranus, Neptune (outer planets), Earth, Venus, Mars, and Mercury (inner planets) A planet is a large, rounded astronomical body that is generally required to be in orbit around a star, stellar remnant, or brown dwarf, and is not one itself. [1]
Animations of the Solar System's inner planets orbiting. Each frame represents 2 days of motion. Animations of the Solar System's outer planets orbiting. This animation is 100 times faster than the inner planet animation. The planets and other large objects in orbit around the Sun lie near the plane of Earth's orbit, known as the ecliptic ...
The smallest known extrasolar planet that is likely a "gas planet" is Kepler-138d, which has the same mass as Earth but is 60% larger and therefore has a density that indicates a thick gas envelope. [16] A low-mass gas planet can still have a radius resembling that of a gas giant if it has the right temperature. [17]
The principal elements that compose rocky planets, which are magnesium, iron, oxygen, carbon, and silicon, are assumed to be universal in the interiors of these planet types. [4] The abundance of these elements, as well as the heating and cooling processes they undergo during planet formation, are responsible for the planet's final composition.