Space Topics: Asteroids and Comets
The Year in Pictures: 2008
First Triple Near-Earth Asteroid
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Triple asteroid 153591 (2001 SN263)
Credit: Arecibo Observatory
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Astronomers training Puerto Rico’s great Arecibo radio telescope on
a close-passing asteroid discovered
that the small body was actually three. The largest component rotates faster
than the smaller ones, spreading it out in this radar image. Although other
triple-asteroid systems are known to exist, this is the first near-Earth triple.
It is also unusual because of the similar size of the three components—from
top to bottom, they are about 0.4, 2.0, and 1.0 kilometers (1,000, 7,000,
and 3,000 feet) in diameter. The three objects look dissimilar in size
here because the width of an object in a radar image is related to how
fast it is rotating, not its actual diameter; faster rotators appears wider.
The Arecibo radio telescope is a critical facility for the study of the
nature and orbits of near-Earth asteroids and is threatened
with closure in 2011
due to a funding standoff between the National Science Foundation and NASA.
Arecibo Observatory
The 300-meter (1,000-foot) dish of the Arecibo Radio Telescope in Arecibo, Puerto Rico, the largest in the world.
Credit: NAIC - Arecibo Observatory, a facility of the NSF
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