Asteroids Spin Faster Due to Solar Power, Studies Show

Brian Handwerk
for National Geographic News
March 7, 2007

Sunlight can speed up or slow down the spin of small asteroids, according to a trio of related papers appearing this week. The discovery offers the first direct evidence of a predicted asteroid behavior.

"The solar system is a very dynamic place, and our star affects all worlds—even small ones," said Patrick Taylor, a graduate student at Cornell University in New York State.

Taylor co-authored two studies that will appear tomorrow in the early online journal Science Express.

The third study, led by Mikko Kaasalainen of the University of Helsinki in Finland, appears today in the early online edition of the journal Nature.

All three papers looked at a phenomenon called the YORP (Yarkovsky-O'Keefe-Radzievskii-Paddack) effect.

When the sun warms an asteroid's surface, the rocky object reradiates heat into the void (related: asteroid facts).

Heat emissions produce a slight recoil that alters the asteroid's spin—the same principle by which light shined on a pinwheel can sometimes cause it to rotate even without a breeze.

The YORP effect alters the asteroid's rate of rotation and the direction it spins on its axis based on the object's size and shape. More asymmetrical asteroids are more susceptible to YORP.

Solving Asteroid Puzzles?

YORP's tiny torque is almost imperceptible in real time. The asteroid in which Taylor observed the effect was seen to be rotating faster by only about a millisecond a year.

Another asteroid studied by Kaasalainen and colleagues also increased its spin, gaining an extra rotation around its axis over the past 40 years.

Yet the effect's potential impact can be significant.

Continued on Next Page >>


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