Jimmy Westlake: Spot an asteroid
February 3, 2010
If the world was surprised in 1801 when Italian astronomer Giuseppe Piazzi announced his discovery of the minor planet Ceres orbiting between the major planets Mars and Jupiter, it was shocked when, one year later, German astronomer Heinrich Olbers found a second minor planet in the same region of space. Subsequent searches then turned up two more minor planets: Juno in 1804 and Olbers' second discovery, Vesta, in 1807. Olbers proposed that we were seeing the fragments of a disrupted planet and predicted that many more pieces might be awaiting discovery.
Olbers may have been wrong with his theory of a disrupted planet, but he was right about one thing — 203 years after the discovery of Vesta, astronomers have catalogued and named thousands of minor planets, now collectively called the asteroids.
Asteroid No. 1002 is named Olbersia in honor of Heinrich Olbers.
Although Ceres is by far the largest of the asteroids at 595 miles in diameter (bigger than Colorado), it is not the brightest of the asteroids. That honor goes to Olbers' asteroid Vesta. Because of its light-colored, reflective surface, Vesta shines brightly in the sunshine and, when closest to Earth, can be glimpsed with the unaided eye if one knows when and where to look.
This month, asteroid Vesta is moving through the stars of the constellation Leo and will be closest to Earth (132 million miles away) on the night of Feb. 16 to 17, providing an excellent opportunity for anyone with a pair of binoculars to spot their first asteroid. At that time, it will be an easy binocular target and might be barely visible to the unaided eye in a dark sky.
As fate would have it, Vesta will be positioned right beside the bright star named Algieba (Gamma Leonis) on the night of closest approach, making identification much easier. Algieba is a famous naked-eye double star near the even brighter star Regulus in the head of Leo the Lion. On the night of Feb. 16, Vesta will be positioned smack dab between the two components of this naked-eye double star. Vesta will be the faintest of the three objects but not by much. Looking the night before and the night after will help clinch the identification because of the asteroid's slow motion relative to the two stars. Algieba will be located due east and about a third of the way up in the sky at 8 p.m. Feb. 16. The orange-colored planet Mars will be shining brightly a little more than a hand-span above Algieba and Vesta.
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Our best eye-in-the-sky, the Hubble Space Telescope, has given us some tantalizing if fuzzy images of Vesta showing vague surface features, but, if all goes according to plan, the veil will be lifted forever in July 2011 when NASA's DAWN spacecraft arrives at Vesta and drops into orbit around Mr. Olbers' asteroid. Studying this distant cousin of Earth's at close range could shed much light on the formation of our own planet and the entire solar system. For mission updates, visit the DAWN home page at http://dawn.jpl.nasa.gov.
Professor Jimmy Westlake teaches astronomy and physics at Colorado Mountain College's Alpine Campus. He is an avid astronomer whose photographs and articles have been published all around the world. His "Celestial News" column appears weekly in the Steamboat Pilot & Today newspaper. His "Cosmic Moment" radio spots can be heard on local radio station KFMU. Also, check out Jimmy's Web site at http://www.jwestlake.com.
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