Sunlight can cause asteroids to spin more quickly, scientists said Wednesday, showing anew just how dynamic a place our solar system can be.
International teams of scientists studying two asteroids, one about a mile wide and the other about 375 feet wide, confirmed a previously unproven theory that sunlight can affect the rotation of asteroids because they tend to be irregularly shaped and not perfectly round.
Stephen Lowry of Queen's University Belfast in Northern Ireland said the findings boost the understanding of the physical properties and dynamics of asteroids -- hunks of metal and rock rattling around in space.
"This is important as asteroids are leftovers from the formation of the solar system, along with comets, and so by studying them we gain insights into what the solar system was like some 4.5 billion years ago," Lowry said by e-mail.
In research appearing in the journals Nature and Science, the scientists focused on the so-called YORP effect, named for four scientists who inspired the theory.
The idea is the sun's heat serves as a propulsion engine on the irregular features of an asteroid's surface. "YORP can accelerate or decelerate the rotation rate," Mikko Kaasalainen of the University of Helsinki in Finland said by e-mail.
When sunlight hits the asteroid, the solar energy is absorbed and then radiated back into space. When the asteroid is not spherical, this can create a push off parts of its surface that alters its spin.
"Depending on the exact shape, the effect on the entire asteroid's surface can lead to a net torque, which can slowly alter the time it takes the asteroid to make one full revolution," Lowry said.
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