Fast-Rotating Asteroid Winks For Astronomer's Camera

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DC Agle (818) 393-9011
Jet Propulsion Laboratory, Pasadena, Calif.
agle@jpl.nasa.gov

Feature: 2011-118 April 14, 2011

Fast-Rotating Asteroid Winks For Astronomer's Camera

Video imaging of newly discovered asteroid 2011 GP59 shows the object appearing to blink on
and off about once every four minutes.

Amateur astronomers, including Nick James of Chelmsford, Essex, England, have captured
video of the interesting object. James generated this video of GP59 on the night of Monday,
April 11. The video, captured with an 11-inch Schmidt-Cassegrain telescope, is a compilation of
137 individual frames, each requiring 30 seconds of exposure. At the time, the asteroid was
approximately 3,356,000 kilometers (2,081,000 mile) distant. Since then, the space rock has
become something of a darling of the amateur astronomy community, with many videos
available. (Here is one recent posting: http://www.youtube.com/watch?v=O7wsAZNr56E )

"Usually, when we see an asteroid strobe on and off like that, it means that the body is elongated
and we are viewing it broadside along its long axis first, and then on its narrow end as it rotates
," said Don Yeomans, manager of NASA's Near-Earth Object Program Office at the Jet
Propulsion Laboratory in Pasadena, Calif. "GP59 is approximately 50 meters [240 feet] long, and
we think its period of rotation is about seven-and-a-half minutes. This makes the object's
brightness change every four minutes or so."

2011 GP59 was discovered the night of April 8/9 by astronomers with the Observatorio Astronomico de Mallorca in Andalusia, Spain. It will make its closest approach to Earth on April 15 at 19:09 UTC (12:09 p.m. PDT) at a distance just beyond the moon's orbit - about 533,000 kilometers (331,000 miles).

"Although newly discovered, the near-term orbital location of asteroid 2011 GP59 can be
accurately plotted," said Yeomans. "There is no possibility of the small space rock entering
Earth's atmosphere during this pass or for the foreseeable future."

NASA detects, tracks and characterizes asteroids and comets passing close to Earth using both ground- and space-based telescopes. The Near-Earth Object Observations Program, commonly called "Spaceguard," discovers these objects, characterizes a subset of them, and plots their orbits to determine if any could be potentially hazardous to our planet.

JPL manages the Near-Earth Object Program Office for NASA's Science Mission Directorate in
Washington. JPL is a division of the California Institute of Technology in Pasadena.

More information about asteroids and near-Earth objects is at:
http://www.jpl.nasa.gov/asteroidwatch .

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