A mysterious planet, called Planet 9 or Planet X, may be hidden on the edge of our solar system. Will we ever find this world?
PLanet Nine may be orbiting away from the Sun, on the edge of our solar system. Astronomers, seeing strange irregularities in the orbits of the outer planets, suspect that another unknown planet may orbit beyond the eight we know today.
The number of known planets in our solar system has increased and decreased over time. Of the six worlds known to ancient people (including Earth), astronomers have found the planets Uranus and Neptune.
Uranus was first seen in 1781, and seventy years later, astronomer Giuseppe Piazzi announced his discovery of an “eighth planet”, which orbits between Mars and Jupiter. This object, Ceres, was found by the largest member of the main asteroid belt, and was classified as such in 1851. At that time, the solar system was said to contain 13 planets (including Neptune, first seen in 1846) , and the The number of recognized planets was reduced to only eight members.
[Read: The oceans of Jupiter’s moon Europa may be habitable, according to NASA]
In 1930, Clyde Tombaugh encountered Pluto, known for decades as the ninth planet. This distinction lasted until 2006, when Pluto was “downgraded” to the dwarf planet class. However, Ceres was also named for this group, recognizing its unique characteristics.
Despite Pluto’s classification as a dwarf planet, it is now recognized as the first Trans-Neptunian Object (TNO) and the first member of the Kuiper Belt to be found. Today, we know of many smaller bodies beyond Neptune: 316 were recently discovered in just one study.
