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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).
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).
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]
Over 200 asteroids are known to be larger than 100 km, [63] and a survey in the infrared wavelengths has shown that the asteroid belt has between 700,000 and 1.7 million asteroids with a diameter of 1 km or more. [64] The number of asteroids in the main belt steadily increases with decreasing size.
Vesta was the fourth asteroid to be discovered, hence the number 4 in its formal designation. The name Vesta, or national variants thereof, is in international use with two exceptions: Greece and China. In Greek, the name adopted was the Hellenic equivalent of Vesta, Hestia (4 Εστία); in English, that name is used for 46 Hestia (Greeks use ...
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 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 ...
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 ...