Nature will be putting on a light show this Earth Day, with the peak of the annual Lyrid meteor shower on Friday night.
"Considered a minor but pretty show, the Lyrids generally produce up to 20 meteors per hour," said Raminder Singh Samra, a resident astronomer at the H.R. MacMillan Space Centre in Vancouver, Canada.
"However, they have been historically noted to produce meteor storms, when hundreds of meteors are visible per hour. The Lyrids have also been known to produce fireball meteors—generally rare events." Fireballs appear when relatively large pieces of space rock burn up in Earth's atmosphere.
For the Lyrids, the meteor trails appear to radiate from near the brilliant star Vega in the shower's namesake constellation, Lyra.
"Look for Lyra in the east a couple of hours after sunset," Samra said. "It looks like a parallelogram with a smaller triangle connected to one of the corners—the bright star Vega forms one of the tips of the triangle."
By the peak of the shower, in the predawn hours of Saturday, Vega will be shining nearly overhead for stargazers in the Northern Hemisphere.
In Southern Hemisphere skies, the apparent point of origin will be at or below the horizon, so the Lyrids will produce just a sprinkling of meteors.
(See meteor shower pictures from last December.)
Bright Moon to Outshine Meteor Shower?
Unfortunately, during this year's peak the waning gibbous moon will rise around 1 a.m. local time. A gibbous moon is more than half full, so the lunar glare will block out all but the brightest meteors.
"But if you can't get away, seek out a dark urban park and get your eyes dark-adapted. The process of dark adaptation can take up to a half hour and will result in many more meteors being visible.
"However, simple stray light from a street light or cell phone can ruin dark-adapted eyes in seconds."
Lyrids May Offer Meteor Surprise
As with most other annual meteor showers, the Lyrids are thought to be caused by sand grain-size debris left over from a passing comet. (See asteroid and comet pictures.)
When a comet gets close to the sun, its ices vaporize, releasing dust grains and sometimes small lumps of rock. This debris trail then settles into orbit around the sun.
As Earth passes through a comet's particle trail, the dust burns up in our atmosphere, creating the bright streaks we see as meteors. Astronomers think the Lyrids are tied to C/1861 G1 Thatcher, a comet discovered in 1861 that takes 400 years to orbit the sun.
Whether a meteor display offers a shower or a storm depends on where Earth hits the comet's dust trail, said Geza Gyuk, an astronomer with the Adler Planetarium in Chicago.
"Because the ejection of debris from the comet is not uniform, the shape of the debris trail is also not uniform," Gyuk said. "Sometimes the Earth passes through an unusually dense section" of the trail, and that's when sky-watchers may see an uptick in meteor numbers. (Find out why astronomers think the 2011 Draconids will be a meteor storm.)
"But because the structure of this debris trail is not well known, compared to more famous showers"—such as the August Perseids—"predictions for surges have not been developed well for the Lyrids." (See Perseid pictures: "Meteor Shower Dazzles Every August.")
According to Gyuk, the only way to know how good the Lyrids' show will be this year is to go outside on Friday night and look up.