Will meteors from Halley's comet surge?
A possible flurry of "shooting stars" makes this year's Eta Aquarid meteor shower worth a look.
|Eta Aquarid Meteors will pepper the sky before dawn May 5. With the Moon at new phase, observing conditions should be ideal. Astronomy: Roen Kelly|
April 29, 2008
Be on the lookout for a rush of meteors before dawn Monday morning. That's when the annual Eta Aquarid meteor shower reaches maximum activity. Seeing the shower with no interference from the Moon is nice, but there's a possible bonus. Astronomers think the Eta Aquarids could produce more than twice the usual number of meteors.
Meteors are fleeting fiery trails — "shooting stars" — that occur as small solid particles burn up in Earth's atmosphere. Comets shed dust as ice boils off their surfaces and litter their orbits with debris. Meteor showers result when Earth grazes a comet's dusty path and sweeps up some of these particles. Dust shed by Comet 1P/Halley creates the Eta Aquarid shower, so named because the meteors seem to emanate from a common point, or radiant, near the star Eta in the constellation Aquarius.
Meteor-watching is a minimalist activity. No equipment is required — skygazers just need to know when and where to look. Dress warmly, relax in a comfortable chair, and keep an eye on the southeastern sky. It's kind of like fishing.
In Halley's dust
Astronomers give a shower's meteor rate using numbers that express the number of meteors seen each hour by an observer viewing under a clear, dark sky when the radiant is overhead. In most years, by this measure, the Eta Aquarid shower rates 30 meteors per hour. But the radiant never gets overhead before dawn, so observers typically will see far fewer meteors.
This year, though, the rate could more than double. Studies suggest the shower's rates rise and fall in a 12-year cycle. This period hints that Jupiter, the solar system's largest planet, is affecting the debris that creates the shower.
Jupiter orbits the Sun in just under 12 years. Every time it passes closest to the Eta Aquarid track, the orbiting particles feel an extra-strong tug. This results in a wavy track that sometimes places extra dust in Earth's way.
Catch a falling star
The Eta Aquarid shower is best for Southern Hemisphere observers, and the view gets worse the farther north you go. In the United States, the radiant stands only about 15° high in the southeast at 4 A.M. local daylight time. This low altitude will cut the number of visible meteors significantly. Even so, observers can expect a nice show.
The shower produces pleasingly fast and often bright meteors. About 30 percent of the meteors leave behind dimly glowing trails called persistent trains. Some can be seen for as long as a minute.
Although the radiant's low altitude reduces the number of observable meteors for northern observers, there is compensation. Eta Aquarid meteors tend to follow long paths across the sky.
Eta Aquarid meteor shower fast factsThe Eta Aquarids are the first of two annual showers produced by Halley's Comet. The other is the Orionid shower in late October.
Astronomers discovered the shower in 1870 and linked it to Comet Halley just six years later.
Its meteors are among the fastest, entering the atmosphere at 151,000 mph (243,000 km/h).
The meteors average magnitude 3. The brighter ones display a yellowish color.