Study: Uranus Tilted By Multiple Impacts
October 11, 2011 by UPI - United Press International, Inc.
NICE, France, Oct. 10 (UPI) — The planet Uranus was tipped askew to rotate on its side by several cosmic collisions rather than just one as previously thought, French researchers say.
The planet’s spin axis is tilted by 98 degrees, a tilt unmatched by any other planet, including Earth’s 23 degrees.
Scientists have long assumed Uranus was “tipped over” by a collision with an object several times the size of Earth, SPACE.com reported Monday. French astronomers say computer simulations suggest a different scenario involving several smaller impacts.
A single impact would have left Uranus’ moons orbiting in a retrograde motion, the opposite of the planet’s rotation — which is not the case.
Astronomers at the Observatoire de la Cote d’Azur in Nice, France, modified their simulations and found that at least two smaller collisions would leave the moons orbiting in the direction they do in fact follow.
“The fact that Uranus was hit at least twice suggests that significant impacts were typical in the formation of giant planets,” study leader Alessandro Morbidelli said.
The finding suggests the solar system may have experienced more violence than previously thought in its early formation, the researchers said.