Uranus is valgus, the only planet that revolves around its side. Researchers now think they know how it happened: it has been pushed by a stone at least twice as large as Earth.
Detailed computer simulations show that a huge stone crashed on the seventh planet from the Sun, said astronomer Durham University astronomer Jacob Kegerreis, who presented his analysis at a large conference on earth and space science this month.
Uranium is unique in the solar system. The massive planet tilts to the side about 90 degrees, like its five largest moons. Its magnetic field is also crooked and does not go out of poles similar to ours, said NASA chief scientist Jim Green. It is also the only planet that has no internal heat escape from the core. It has rings like Saturn, albeit weak.
"It's very strange," said the planetary scientist Carnegie Institution, Scott Sheppard, who was not part of the study.
Computer simulations show that the collision and change of Uranus – maybe including some or all of the rock that struck – happened within a few hours, said Kegerreis. He produced an animation showing the sudden failure and its consequences.
It is also possible that the large object that overturned Uranus still lurks too far in the Solar System so that we can see it, "Green said. That would explain some of the planet's orbits and would fit the theory that the missing planet X goes around the Sun far beyond Pluto, he said.
Green said that it is possible that many smaller cosmic rocks – Pluto's size – have pushed Uranus, but Kegerreis and Sheppard's studies point to one huge unknown suspect. Green said that a single effect "is right thinking".
The collision occurred from 3 to 4 billion years ago, probably before the larger moons of Uranus were formed. Instead, a disc with materials appeared that eventually converged to form the moons. And when that happened, Uranus' strange inclination acted like a gravitational tidal force, pushing these five large moons to the same incline, Kegerreis said.
It would also create an ice coating that would keep the internal heat of Uranus, said Kegerreis. (Uranium surface is minus 357 degrees, or minus 216 degrees Celsius.)
Ice is the key to Uranus and neighbor of Neptune. Just over ten years ago, NASA reclassified these two planets as "ice giants", not throwing them off with other large planets of the Solar System, gas giants Saturn and Jupiter.
Pluto, which is tiny, farther from the sun, and even officially no longer a planet, has been studied more than Uranus and Neptune. They only got short flights via Voyager 2, a space probe that entered the interstellar space last month.
Uranus and Neptune "are by far the least known planets," said Sheppard.
But that can change. A robotic probe for one or both of these planets is on the last wish list of leading planetary scientists and is likely to be at the top of or next to the next list.
Uranus was named in honor of the Greek god of heaven. Its name often evokes a youthful mood when it is misspelled like a part of the body. (It is pronounced correctly YUR & # 39; -uh-nus.)
"No one laughs when I say Uran," said NASA Green. "They have to figure it out badly to get a giggle."