Look, Listen, Lyrids!
"This is a good year for the Lyrids because the Moon will be almost New when the shower peaks," says astronomy professor George Lebo, a 2001 NASA/Marshall Summer Faculty Fellow. "Barring urban light pollution, the skies should be plenty dark."
Typical Lyrid meteors are about as bright as the stars in the Big Dipper, which makes this shower a good one for beginners. Experienced meteor watchers recall many brilliant Lyrid fireballs from years past. Such meteors, which are brighter than Venus, often leave behind "persistent trains" -- that is, smoky trails that can linger in the night sky for minutes.
Above: Artist Duane Hilton painted this scene of a smoky Lyrid meteor trail dissipating in the pre-dawn sky of California's Owens Valley, with blossoming wild irises in the foreground.
The best time to watch, no matter where you live, will be during the hours before dawn on Sunday between about 2 a.m. and 5 a.m. local time. Simply go outside and look up, generally toward the north. Sky watchers in rural areas should spot a shooting star every few minutes.
Lyrid meteors appear to stream from a point in the sky (called "the radiant") near Vega -- a brilliant blue-white star about three times wider than our Sun. Around 14,000 years ago Earth's wandering spin axis pointed toward Vega -- it, not Polaris, was the North Star. More recently Vega gained fame as an important star in Carl Sagan's movie Contact. If you live at mid-northern latitudes,Vega will lie almost directly overhead before the Sun rises on Sunday morning.
Although Lyrid meteors seem to streak away from the vicinity of Vega, they have nothing to do with that distant star, which is 25 light years away. Lyrid meteoroids are bits of dusty debris shed by comet Thatcher here within our solar system. Earth plows through Thatcher's debris stream with a relative velocity of 49 km/s (110,000 mph!). Meteoroids --usually no bigger than grains of sand-- strike Earth's atmosphere and disintegrate as fiery streaks of light.
The Lyrid shower is prone to occasional outbursts. Most years in April there are no more than 10 to 15 meteors per hour during the shower's peak. But sometimes, when Earth glides through an unusually dense clump of comet Thatcher's debris, the rate increases. For instance, sky watchers in 1982 spotted 90 Lyrids per hour. An even more impressive outburst was documented in 1803 by a journalist in Richmond, Virginia, who wrote:
"Shooting stars. This electrical [sic] phenomenon was observed on Wednesday morning last at Richmond and its vicinity, in a manner that alarmed many, and astonished every person that beheld it. From one until three in the morning, those starry meteors seemed to fall from every point in the heavens, in such numbers as to resemble a shower of sky rockets..." [ref]
What will the Lyrids do in 2001? The only way to know for sure is to go outside on Sunday morning and look up!
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Scientists at the NASA Marshall Space Flight Center Engineering Directorate operate a 24-hour-a-day meteor radar to monitor cosmic debris in the near-Earth environment. The radar's loudspeaker plays directly to the internet, so you can listen to Lyrid radar echoes during the shower. The radar is so sensitive it can register meteors too dim to see with the human eye even under the best observing conditions.
If you can't decide how best to enjoy the Lyrids -- listening or watching -- Dennis Gallagher, a space physicist at the Marshall Space Flight Center, has a solution: "Just point your computer speaker out the window and listen and watch at the same time," he says.
The ongoing Lyrid meteor shower began on April 16th. It will peak on the 22nd and subside on April 25th. The radar is even now detecting some low-level Lyrid activity, with a crescendo expected on Sunday. The best time to listen is during the hours around dawn in Huntsville, Alabama, where the radar is located. Remember that radar echoes from meteors don't fade away when the Sun rises -- so you can continue to hear their "pings" even after daybreak. Huntsville is in the USA's central time zone; thus, prime listening hours will be from 3 a.m. until about 9 a.m. CDT (or from 0800 to 1400 UT).
For updates about the ongoing Lyrid meteor shower, please visit SpaceWeather.com.
Editor's note: The Lyrid meteor shower is best viewed from the northern hemisphere where its radiant lies high in the sky. Southern observers as far south as -30 degrees latitude will spot some Lyrids, but probably no more than a sprinkling. For sky watchers south of the equator, listening to the online radar might be the best way to enjoy the celestial show.Web Links
Right: What does a meteoroid look like? This picture shows one that is only 10 microns across. It was captured by a U2 aircraft high in the stratosphere before it had a chance to burn up or hit the ground. [more information]
Nature's Tiniest Space Junk -- Science@NASA article: Using an experimental radar at the Marshall Space Flight Center, scientists are monitoring tiny but hazardous meteoroids that swarm around our planet.
Comet C/1861 G1 Thatcher, the parent of the Lyrid debris stream, loops around the Sun every ~415 years in an elliptical orbit inclined 80 degrees with respect to the plane of the solar system. Because the comet spends most of its time well away from the planets, it suffers few gravitational perturbations. As a result, the debris stream is very stable and the Lyrid shower has been observed for at least 2600 years.[more information]
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