At their most visible late Saturday night and before dawn Sunday this year, the Perseids occur when Earth and the moon pass through a cloud of rocky particles shed by comet Swift-Tuttle.
Hitting the atmosphere at speeds of almost a hundred thousand miles (160,000 kilometers) an hour, the meteoroids burn up, producing streaks of light—meteors, or shooting stars—each lasting just a fraction of a second.
An exceptionally bright Perseid meteor appears to strike the peak of Mount Rainier, Washington, in 2010. The shooting stars appear to radiate, or shoot from, their namesake constellation, Perseus, which will rise above the local horizon around midnight in the northeastern sky. (See Perseid-viewing diagram.)
In dark, cloudless areas Saturday, the night's first 2012 Perseids should become visible around 10 p.m. local time Saturday, with rates increasing through the night, eventually reaching a rate of one or two shooting stars per minute before dawn.
Perseid meteors streak past stars—shown as arcing streaks in a long-exposure photo—as a over a Bedouin tent near Amman, Jordan, in 2004.
For anyone up to the challenge of capturing the fleeting lunar Perseid impacts this weekend, NASA's Suggs recommends at least an 8-inch (20-centimeter) telescope equipped with a digital video camera and recorder.
On average, amateur astronomers with such equipment can record one or two flashes, only a thirtieth of a second each—too brief for unaided vision.
But if you miss out this time, your next best opportunity to see lunar flashes will be during the annual Geminid meteor shower in mid-December, said Suggs, manager of NASA's Lunar Impact Monitoring Program at Marshall Spaceflight Center in Huntsville, Alabama.
The space rocks and dust that become Perseids are debris cast off by comet Swift-Tuttle. Discovered by U.S. astronomers Lewis Swift and Horace Parnell Tuttle in 1862, Swift-Tuttle would not pass by Earth again until 1992.
With its roughly 130-year orbit, comet Swift-Tuttle is expected in Earthy skies again in 2125. (Get more Perseids facts.)
Photograph courtesy Stéphane Guisard, ESO
A meteor—perhaps a late Perseid—grazes the sky above the Armenian monastery of Geghard in a September 2008 picture submitted to the astronomy-education project the World at Night (TWAN).
In 2012 it may be a struggle to capture Perseids hitting the moon. The densest part of the meteor shower hit the far side of the moon, impossible to see from Earth.
A Perseid meteor streaks over Iran's Alborz mountain range in 2010.
No matter where you are for the 2012 Perseids, glare from the waning crescent moon may obscure some of the fainter meteors a bit when it rises between 1 and 2 a.m. local time. But the interference shouldn't be enough to discourage stargazers from looking skyward—preferably with unaided eyes—for one of the year's best sky shows.