A new, planet-like body has been found on the outer edges of the solar system.
By Akshat Rathi | The Conversation
This object, called 2012VP113, is the second body of its class found since the identification of the dwarf planet Sedna in 2003. It joins an exclusive club composed of some of the strangest objects in the solar system.
The observable solar system can be divided into three regions: the rocky planets including the Earth and asteroids of the inner solar system, the gas giant planets, and the icy Kuiper Belt objects, which include Pluto. The Kuiper belt stretches from beyond Neptune, which is at 30 astronomical units (one astronomical unit, AU, represents the distance between the Earth and the sun), to about 50AU.
Sedna and 2012VP113 are strange objects, because they reside in a region where there should be nothing, according to our theories of the solar system formation. Their orbit is well beyond that of Neptune, the last recognised planet of the solar system, and even beyond that of Pluto, which differs from planets because of its size, unusual orbit, and composition. (Pluto, once considered a planet, is now considered the lead object of a group of bodies called plutinos.)
The closest Sedna, which is 1000km-wide, gets to the sun is about 76AU and for 2012VP113, which is 450km-wide, that distance is 80AU. Their orbits are also at weird inclinations compared to most other solar system objects.
The results of the discovery have been published in Nature. Chadwick Trujillo of Gemini Observatory in Hawaii, who was also involved in finding Sedna, and Scott Shepherd of the Carnegie Institution for Science, who found 2012VP113 with Trujillo, propose that these objects are members of the inner Oort cloud.
The Oort cloud is a hypothetical region that is thought to stretch outwards beyond the Kuiper belt. Beyond 5000AU, the Oort cloud expands out into a sphere centred on the sun. We have no direct evidence that the Oort cloud exists, but indirect evidence comes in the form of comets with extremely elongated orbits.