鈥淚 hope everyone has buckled their seatbelts because the outer solar system just got a lot weirder.鈥� That鈥檚 what Michele Bannister, an astronomer at Queens University, Belfast on Monday.
She was referring to the of a TNO or trans-Neptunian object, something which sits beyond Neptune in the outer solar system. This one is 160,000 times fainter than Neptune, which means the icy world could be less than 200 kilometres in diameter. It鈥檚 currently above the plane of the solar system and with every passing day, it鈥檚 moving upwards 鈥� a fact that makes it an oddity.
The TNO orbits in a plane that鈥檚 tilted 110 degrees to the plane of the solar system. What鈥檚 more, it swings around the sun backwards unlike most of the other objects in the solar system. With this in mind, the team that discovered the TNO nicknamed it 鈥淣iku鈥� after the Chinese adjective for rebellious.
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To grasp how truly rebellious it is, remember that a flat plane is the signature of a planetary system, as a star-forming gas cloud creates a flat disk of dust and gas around it. 鈥淎ngular momentum forces everything to have that one spin direction all the same way,鈥� says Bannister. 鈥淚t鈥檚 the same thing with a spinning top, every particle is spinning the same direction.鈥�
That means anything that doesn鈥檛 orbit within the plane of the solar system or spins in the opposite direction must have been knocked off course by something else. 鈥淚t suggests that there鈥檚 more going on in the outer solar system than we鈥檙e fully aware of,鈥� says at the Harvard-Smithsonian Center for Astrophysics, part of the team that discovered Niku using the Panoramic Survey Telescope and Rapid Response System 1 Survey (Pan-STARRS 1) on Haleakala, Maui.
And it鈥檚 the unknown that excites astronomers. 鈥淲henever you have some feature that you can鈥檛 explain in the outer solar system, it鈥檚 immensely exciting because it鈥檚 in some sense foreshadowing a new development,鈥� says at the California Institute of Technology.
Planet Nine
He should know 鈥� Batygin was one of two astronomers who earlier this year announced that the presence of another highly inclined group of objects could be pointing toward a large undiscovered world, perhaps 10 times as massive as Earth, lurking even further away 鈥� the so-called Planet Nine.
Upon further analysis, the new TNO appears to be part of another group orbiting in a highly inclined plane, so Holman鈥檚 team tested to see if their objects could also be attributed to the gravitational pull of Planet Nine.
It turns out Niku is too close to the solar system to be within the suggested world鈥檚 sphere of influence, so there must be another explanation. The team also tried to see if an undiscovered dwarf planet, perhaps similar to Pluto, could supply an explanation, but didn鈥檛 have any luck. 鈥淲e don鈥檛 know the answer,鈥� says Holman.
Bannister couldn鈥檛 be more thrilled. 鈥淚t鈥檚 wonderful that it鈥檚 so confusing,鈥� she says. 鈥淚鈥檓 looking forward to seeing what the theoretical analysists do once they get their hands on this one.鈥�
But Batygin isn鈥檛 jumping up and down just yet. 鈥淎s they say in the paper, what they have right now is a hint,鈥� he says. 鈥淚f this hint develops into a complete story that would be fantastic.鈥�
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