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Planet Nine is a hypothetical ninth planet in the outer region of the Solar System. [2] [4] Its gravitational effects could explain the peculiar clustering of orbits for a group of extreme trans-Neptunian objects (ETNOs), bodies beyond Neptune that orbit the Sun at distances averaging more than 250 times that of the Earth i.e. over 250 astronomical units (AUs).
Below are the descriptions of the three largest bodies in the asteroid belt. They are all considered to be relatively intact protoplanets, a precursor stage before becoming a fully-formed planet (see List of exceptional asteroids): [143] [144] [145] Ceres (2.55–2.98 AU) is the only dwarf planet in the asteroid belt. [146]
An asteroid is a minor planet —an object that is neither a true planet nor an identified comet — that orbits within the inner Solar System. They are rocky, metallic, or icy bodies with no atmosphere, classified as C-type (carbonaceous), M-type (metallic), or S-type (silicaceous).
The Oort cloud (/ ɔːrt, ʊərt /), [1] sometimes called the Öpik–Oort cloud, [2] is theorized to be a vast cloud of icy planetesimals surrounding the Sun at distances ranging from 2,000 to 200,000 AU (0.03 to 3.2 light-years). [3][note 1][4] The concept of such a cloud was proposed in 1950 by the Dutch astronomer Jan Oort, in whose honor ...
There is evidence that the formation of the Solar System began about 4.6 billion years ago with the gravitational collapse of a small part of a giant molecular cloud. [ 1 ] Most of the collapsing mass collected in the center, forming the Sun, while the rest flattened into a protoplanetary disk out of which the planets, moons, asteroids, and ...
The following is a list of Solar System objects by orbit, ordered by increasing distance from the Sun. Most named objects in this list have a diameter of 500 km or more. The Sun, a spectral class G2V main-sequence star. The inner Solar System and the terrestrial planets. Mercury. Mercury-crossing minor planets. Venus. Venus-crossing minor planets.
The Kuiper belt (/ ˈkaɪpər / KY-pər) [1] is a circumstellar disc in the outer Solar System, extending from the orbit of Neptune at 30 astronomical units (AU) to approximately 50 AU from the Sun. [2] It is similar to the asteroid belt, but is far larger—20 times as wide and 20–200 times as massive. [3][4] Like the asteroid belt, it ...
Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest include planets, moons, stars, nebulae, galaxies, meteoroids, asteroids, and comets.