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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 (AU).
The search began in the mid-19th century and continued at the start of the 20th with Percival Lowell's quest for Planet X. Lowell proposed the Planet X hypothesis to explain apparent discrepancies in the orbits of the giant planets, particularly Uranus and Neptune, [2] speculating that the gravity of a large unseen ninth planet could have ...
Eris was discovered in January 2005 by a Palomar Observatory–based team led by Mike Brown and verified later that year. It was named in September 2006 after the Greco–Roman goddess of strife and discord. Eris is the ninth-most massive known object orbiting the Sun and the sixteenth-most massive overall in the Solar System (counting moons).
It is the ninth-largest and tenth-most-massive known object to directly orbit the Sun. It is the largest known trans-Neptunian object by volume, by a small margin, but is less massive than Eris. Like other Kuiper belt objects, Pluto is made primarily of ice and rock and is much smaller than the inner planets.
These lists contain the Sun, the planets, dwarf planets, many of the larger small Solar System bodies (which includes the asteroids), all named natural satellites, and a number of smaller objects of historical or scientific interest, such as comets and near-Earth objects.
This is a list of the hottest exoplanets so far discovered, specifically those with temperatures greater than 2,500 K (2,230 °C; 4,040 °F). For comparison, the hottest planet in the Solar System is Venus , with a temperature of 737 K (464 °C; 867 °F).
The sizes are listed in units of Jupiter radii (R J, 71 492 km).This list is designed to include all planets that are larger than 1.7 times the size of Jupiter.Some well-known planets that are smaller than 1.7 R J (19.055 R 🜨 or 121 536.4 km) have been included for the sake of comparison.
Additional planets in the outer reaches of the Solar System, such as a ninth planet beyond Neptune or especially a tenth beyond Pluto (between the 1930 discovery of Pluto and its reclassification from planet to dwarf planet in 2006), appear regularly. Many different names for this hypothetical outermost planet have been used, the most common ...