Asteroid Juno Grabs the Spotlight

Feature September 16, 2009

Asteroid Juno Grabs the Spotlight

Toward the end of September, the sun will turn a spotlight on the asteroid Juno,
giving that bulky lump of rock a rare featured cameo in the night sky. Those who
get out to a dark, unpolluted sky will be able to spot the asteroid's silvery glint near
the planet Uranus with a pair of binoculars.

"It can usually be seen by a good amateur telescope, but the guy on the street
doesn't usually get a chance to observe it," said Don Yeomans, manager of NASA's
Near Earth Object Program Office at JPL. "This is going to be as bright as it gets
until 2018."

Juno, one of the first asteroids discovered, is thought to be the parent of many of
the meteorites that rain on Earth. The asteroid is composed mostly of hardy silicate
rock, which is tough enough that fragments broken off by collisions can often
survive a trip through Earth's atmosphere.

Though pockmarked by bang-ups with other asteroids, Juno is large; in fact, it is
the tenth largest asteroid. It measures about 234 kilometers (145 miles) in
diameter, or about one-fifteenth the diameter of the moon.

The asteroid, which orbits the sun on a track between Mars and Jupiter, will be at
its brightest on Sept. 21, when it is zooming around the sun at about 22 kilometers
per second (49,000 miles per hour). At that time, its apparent magnitude will be
7.6, which is about two-and- a-half times brighter than normal. The extra
brightness will come from its position in a direct line with the sun and its proximity
to Earth. (The asteroid will still be about 180 million kilometers [112 million miles]
away, so there is no danger it will fall towards Earth.)

Skywatchers with telescopes can probably see Juno from now until the end of the
year, but it is most visible to binoculars in late September. On or before Sept. 21,
look for Juno near midnight a few degrees east of the brighter glow of Uranus and
in the constellation Pisces. It will look like a gray dot in the sky, and each night at
the end of September, it will appear slightly more southwest of its location the
night before. By Sept. 25, it will be closer to the constellation Aquarius and best
seen before midnight.

For more information: http://neo.jpl.nasa.gov/ .

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