A goblin lurks at the edge of our solar system. Far beyond Pluto, astronomers have found a new dwarf planet that follows the most distant orbit yet confirmed, reaching some 2300 times farther from the sun than Earth’s. Nicknamed “The Goblin” thanks to its discovery around Halloween 2015, 2015 TG387 takes 40,000 years to orbit the sun, researchers report online today on the preprint server arXiv.
The discovery of the 300-kilometer-wide planet was a lucky one. For 99% of its orbit, it would have been too faint to see, but astronomers caught it—using the Subaru 8-meter telescope in Hawaii—as it moved toward its closest approach to the sun. The Goblin now joins a small group of extreme solar system objects whose orbits, which are beyond the gravitational reach of Uranus and Neptune, hint at tugs from a hypothesized, but not yet observed, Planet Nine, hidden in the fringes of the solar system.