March 15, 2007

Profs Link Light to Asteroid Rotation Speed

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Prof. Jean-Luc Margot, astronomy, and Patrick Taylor grad recently made a discovery of “astronomical” proportions by proving that particles of light have enough force to cause asteroids to spin faster. Their research, in conjunction with the work of scientists from Queen’s University in Ireland, revealed the first explicit evidence of the Yarkovsky-O’Keefe-Radzievskii-Paddack (YORP) Effect, named after the astronomers credited for its discovery.

“Who would think that sunlight could change how asteroids spin?” said Taylor concerning the recent findings. “It may not solve world hunger, but it’s pretty neat.”

Since the summer of 2001, these two teams of scientists have been tracking the asteroid 2000 PH5. Neither of the two teams, however, initially intended to prove the long theorized YORP Effect. It was not until two to three years into their research that it became apparent that the orbit of the asteroid was inexplicably changing. From that point on, collaboration was necessary.

Margot and Taylor use the Cornell-affiliated Arecibo Observatory in Puerto Rico to produce radar observations of the asteroid. The Arecibo Telescope, the largest single aperture telescope ever built, assisted Margot and Taylor in constructing an estimated shape and high-resolution image of the asteroid. The team at Queen’s University was responsible for the optical observations, finding the change in light intensity as the asteroid rotated. The two teams were thus able to compare the recorded rotation of the asteroid with the structural observations and prove the existence of the YORP Effect.

Although the YORP Effect has been considered a probable cause for asteroid orbit change for years, up until now there has been no definitive evidence of the theory, which states that the photons from the sun change the rotation speed of an object. The heat from the photons is re-radiated in a slightly different direction than the original course and it causes a minute change in the orbit of the object.

According to Dr. Stephen C. Lowry, team leader of the Queens University research group, “[The change from the photons] gives rise to a gentle recoil effect.” This gentle repercussion of the sun’s light will reduce 2000 PH5’s rotation by half in approximately 500,000 years. Although this may seem inconsequential, this relatively short-term effect, considering the solar system is 4.6 billion year old, also leads to the formation of binary asteroids, resulting from the centrifugal force that the faster spin creates.

The verification of the YORP Effect “shows the public that the solar system is a very dynamic place. A lot can change over long periods of time,” said Margot.