Sky watch: Asteroid Vesta's opposition

Mention our solar system, and most people conjure up images of the sun, the planets and their attendant moons, and perhaps even some of the most famous comets ever to grace our skies. But what about the asteroids?

Poor li'l asteroids -- they seldom get much attention. Too bad, too. There may be more asteroids than anything else orbiting our sun. Most tend to lie in the void between Mars and Jupiter and range in size from tiny pebbles to chunks of rock as large as mountains.

But this summer, one of these lumps has become a "star" itself. Its name is Vesta, and you've probably heard of it because on July 15 NASA's robotic spacecraft Dawn arrived at the asteroid and entered orbit around it. In the intervening weeks, Dawn has begun producing crisp images of this distant body's cratered surface.

To learn more about this exciting mission -- perhaps a precursor to a future human voyage to the asteroid -- and to keep up with the newest and most fantastic images, visit dawn.jpl.nasa.gov.

Since their discovery of Vesta little more than two centuries ago, astronomers have learned that the 350-mile-diameter asteroid reflects one-quarter of all sunlight falling onto its surface -- the moon reflects only 12 percent -- and this makes the asteroid "shiny." Vesta is the brightest of all asteroids, occasionally appearing to binoculars or the unaided eye from a dark, rural site. And right now is one of those times -- Vesta's "opposition."

Opposition is a time when a solar system body appears opposite in the sky from the sun. It's during this time that it lies closest to Earth and shines brightest. Vesta achieves its opposition point this year Aug. 5, when it lies 114,200,000 miles from our planet. To find Vesta, gaze low toward the southeast just after dark. You'll find the v-shaped constellation of Capricornus, among whose stars the distant asteroid can now be found. Locate Capricornus and the rough position of Vesta, but for more detailed instructions and maps to find it as it drifts among the stars from night to night, visit: dawn.jpl.nasa.gov/news/observing_vesta.asp.