Scientists at the University of Durham (UK) have obtained evidence that several billion years ago, an unknown planet twice the size of Earth collided with Uranus. This explains why the axis of Uranus lies "on its side", unlike all other planets in the solar system. In this case, the celestial body may turn out to be the desired ninth planet. This was announced in a press release on Phys.org.
The hypothesis of the collision of Uranus with a large planetesimal was proposed several decades ago, but not all researchers agree with it. Another version was put forward, according to which the axis of rotation was "shaken" by a large satellite, which then disappeared.
The simulation results showed that the collision with a large object and the final change in the axis of rotation occurred in a few hours. In this case, a collision with several smaller celestial bodies is considered by astronomers as less likely. According to scientists, the planet that crashed into Uranus may still be present in the solar system and is far beyond Pluto's orbit, that is, it is the ninth planet that astronomers have been looking for for several years.
The planetary catastrophe occurred 3-4 billion years ago, probably before the satellites of Uranus were formed. Then the ice giant was a protoplanet with a disk of gas and dust, from which moons later arose. The tilt of Uranus 'axis affected the tilt of the satellites' orbits and the orientation of their own axes. The collision also led to the formation of an outer shell that traps heat inside the planet (the gas giant's tropopause temperature is minus 216 degrees Celsius).
Ice giants are a class of planets that consist of ammonia, methane, hydrogen sulfide in the form of supercritical fluids. In the solar system, these are Uranus and Neptune. Hydrogen and helium account for 20 percent of the mass, which distinguishes them from gas giants such as Jupiter and Saturn (the share of hydrogen and helium is 80 percent).
