A TEAM of North-East researchers have used super computer simulations to show how one of the solar system’s planets came to be tilted after being hit in a ‘cataclysmic’ collision around four billion years ago.

The astronomers from Durham University led an international team of experts to investigate how Uranus came to be tilted on its side and what consequences a giant impact would have had on the planet’s evolution.

After carrying out the first high-resolution computer simulations of different massive collisions with the ice giant to try to work out how the planet evolved, they confirmed a previous study which found Uranus’ tilted position was caused by a collision with a massive object, roughly twice the size of Earth.

Lead author Jacob Kegerreis, PhD researcher in Durham University’s Institute for Computational Cosmology, said: “Uranus spins on its side, with its axis pointing almost at right angles to those of all the other planets in the solar system. This was almost certainly caused by a giant impact, but we know very little about how this actually happened and how else such a violent event affected the planet.

“We ran more than 50 different impact scenarios using a high-powered super computer to see if we could recreate the conditions that shaped the planet’s evolution.

“Our findings confirm that the most likely outcome was that the young Uranus was involved in a cataclysmic collision with an object twice the mass of Earth, if not larger, knocking it on to its side and setting in process the events that helped create the planet we see today.”

The researchers say the ice giant was most likely hit by a young proto-planet made of rock and ice during the formation of the solar system about four billion years ago.

The simulations also suggested debris from the impactor could form a thin shell near the edge of the planet’s ice layer, trapping heat from Uranus’ core, which could help explain the planet’s extremely cold atmosphere of -216 degrees Celsius.

There has been a question mark over how Uranus managed to retain its atmosphere when a violent collision might have been expected to send it hurtling into space.

According to the simulations, this can most likely be explained by the impact object striking a grazing blow, strong enough to affect the tilt but so the planet could retain its atmosphere.

The research could also help explain the formation of Uranus’ rings and moons, with the simulations suggesting the impact could jettison rock and ice into orbit around the planet, which could have them clumped together to form the planet’s inner satellites and perhaps altered the rotation of any pre-existing moons.

Uranus is similar to the most common type of exoplanets – planets found outside of our solar system – and the researchers hope their findings will help explain how these planets evolved and understand more about their chemical composition.

Co-author Dr Luis Teodoro, of the BAER/NASA Ames Research Center, said: “All the evidence points to giant impacts being frequent during planet formation, and with this kind of research we are now gaining more insight into their effect on potentially habitable exoplanets.”

The research was funded by the Science and Technology Facilities Council, The Royal Society, NASA and Los Alamos National Laboratory.

The findings are published in The Astrophysical Journal.