SKYWATCH

Comet Swift-Tuttle to Reveal Its Showering Achievement in Mid-August

By Blaine P. Friedlander Jr.
Special to The Washington Post
Sunday, July 27, 2008

The annual Perseid meteor shower -- perfectly punctual specks of cosmic dirt puncturing Earth's atmosphere at high speed -- peaks the night-early morning of Aug. 11-12. Barring cloudy skies, these shooting stars are best seen in the wee hours of the morning.

The evening of Aug. 11 begins with Jupiter and the gibbous moon loitering in the eastern heavens. The bright moon sets about 1:51 a.m. in the west Aug. 12, according to the U.S. Naval Observatory. This makes the night sky dark enough to enjoy meteors.

Get away from city lights, says Bill Cooke of NASA's Meteoroid Environment Office at Marshall Space Flight Center. He says sky gazers might see a few Perseid meteors at nightfall Aug. 11 because the constellation Perseus-- from which the meteors appear to originate -- rises in the east. These few early meteors skim off Earth's atmosphere, he says, making them long, slow and colorful.

The American Meteor Society says a good time for meteor hunting might be between 4 and 5 a.m. Aug. 12. Dark locations are best, but in metropolitan areas, the visibility rate can be as low as 25 meteors an hour -- probably giving sky watchers only a handful to view in an hour.

Meteors occur when the Earth cuts through the dirty old paths of comets. In this case, Earth slices through Comet Swift-Tuttle's trail. The specks strike Earth's atmosphere and burn up, creating brilliant streaks of light. The comet's co-discoverer, astronomer Horace Tuttle, died in 1923 and is buried in an unmarked grave near Seven Corners in Falls Church.

Cosmic Connections

Jupiter, the planetary king of the solar system, is high in the southeast sky at dusk and spends next month hanging out in the constellation Sagittarius. Early in August, it sets about 3 a.m. The large gaseous planet gleams at a brilliant negative second magnitude, making it easy to find from urban locations. To the naked eye, Jupiter looks like a bright, white object.

Busier than the Beltway at rush hour, the western sky at dusk is full of planets next month: Mars, Saturn and Venus meet. Lining up single-file along the sun's apparent path in the sky, the planets entertain sky gazers for less than an hour after sunset. At the beginning of August, dim Mars is the highest, then Saturn, and Venus sits closest to the sun.

By mid-August, Saturn and Venus convene low on the western horizon, if you can see it at all. Mercury joins the ringed Saturn and Venus to form a tight-knit group in mid-August. By the end of the month, Venus, long since past Saturn, nudges closer to Mars. Use binoculars to find these planets, but be careful. Look for them after sunset. Never use binoculars to view the sun.

Events

· Saturday-- The heavens are filled with planets, stars and cosmic objects in "Exploring the Sky" at Rock Creek Park, held by the National Park Service and the National Capital Astronomers. Meet near the nature center in the field south of Military and Glover roads NW. 8:30 p.m. Information: 202-895-6070.

· Aug. 5-- Astronomer Rosemary Killen talks about "Tenuous Atmospheres: Neutrals, Ions and Dust in the Solar System" at an open house, University of Maryland observatory, College Park. See the heavens after, weather permitting. 9 p.m. Information: 301-405-6555; http://www.astro.umd.edu/openhouse.


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