Our solar system just got a little spookier. A new dwarf planet called The Goblin has been discovered orbiting the sun in the hinterland beyond Pluto, and its elongated path hints that the long-sought Planet X may be travelling through the outer reaches of the solar system as well.
This new dwarf planet, officially called 2015 TG387, is likely a ball of ice and is about 300 kilometres in diameter. It was first spotted by a team of astronomers using the Subaru telescope in Hawaii in October 2015, hence its Halloween-themed name. The International Astronomical Union’s Minor Planet Center announced the discovery on 1 October 2018.
Its extremely elongated orbit means that at times it is 2300 times as far from the sun as Earth is, and it never gets closer to the sun than about twice as far out as Pluto. The dwarf planet moves so slowly that it took years to confirm its orbit with multiple observations.
“Currently we would only detect 2015 TG387 when it is near its closest approach to the sun. For some 99 per cent of its 40,000-year orbit, it would be too faint to see,” said David Tholen at the University of Hawaii in a statement.
He and his colleagues found The Goblin during their hunt for the hypothetical Planet X, a large planet believed to be lurking at the edge of the solar system that may account for disturbances in the orbits of smaller objects like The Goblin. The gravity of such a large planet would tug on smaller objects as they pass by, potentially herding them into a cluster of objects orbiting together – like the one The Goblin is part of.
The most distant objects in our solar system tend to have similar elongated orbits. The team ran simulations that included a Super-Earth-like planet in the distant solar system, and found that such a planet would stabilise The Goblin’s orbit.
“These simulations do not prove that there’s another massive planet in our solar system, but they are further evidence that something big could be out there,” said Chad Trujillo at North Arizona University in a statement.
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