If you live in North America, Saturday night will bring one annual meteor shower you won't have to set an alarm clock to see.
The Draconids are coming, and astronomers who forecast these events suggest these meteors could be slicing across the sky at a rate of from 500 to 1,000 an hour at the shower's peak.
Before you get too excited, however, some caveats:
1) The shower is expected to peak between 3 p.m. and 5 p.m. Eastern Daylight Time, meaning the folks in the best position to see the show live in the Middle East, North Africa, and parts of Europe. The shower will appear over North America as it's waning.
2) The moon will be up, and it's only a couple of days away from full-moon status. That means it may be hard to see all but the brightest meteors – from a shower known for a high proportion of dim bulbs.
Still, "if I were a member of the general public, I'd sure stick my head out tomorrow night just in case," says Bill Cooke, who heads NASA's Meteoroid Environment Office at the Marshall Spaceflight Center in Huntsville, Ala. Typically the Draconids peak at about 20 meteors an hour, astronomers say.
The meteors will appear to travel from a point near the head of Draco the Dragon, a constellation visible all year for most people with a view of the northern sky.
The shower's source is a comet known as 21P/Giacobini-Zinner. It's a member of the Jupiter Family of comets, objects that come from the Kuiper Belt, a broad swath of ice-rich orbs that lies beyond Neptune.
The comet orbits the sun once every 6.6 years, leaving tendrils of dust in its wake. This year's expectations for large numbers of meteors is based on projections that the Earth will encounter three or four of these tendrils, including one that touched off a dazzling display in 1900 that yielded 600 meteors an hour at its peak. That was the year the comet was first detected.
Scientists have recorded at least two occasions during the last century when the Draconids topped 10,000 meteors an hour.
The unusually intense shower poses an increased risk to satellites, Dr. Cooke notes. Some satellites can ride out the storm, while others – those with cameras or telescopes – likely will be turned so the delicate optics face away from the oncoming dust grains.
As for the International Space Station, he adds, it's sufficiently armored to withstand hits from the Draconids. But, he adds, don't look for any astronauts to conduct spacewalks during the shower.
"Most years, we pass through gaps between filaments, maybe just grazing one or two as we go by," Cooke said in a statement beforehand. "Occasionally, though, we hit one nearly head on – and the fireworks begin."
Although for North American observers, the peak comes during daylight, Peter Jenniskens, with the SETI Institute in Mountain View, Calif., notes that some of the brightest meteors could still be visible with binoculars. He suggests looking north, between 10 and 40 degrees above the horizon, especially around 4 p.m. Eastern Daylight Time.
He also suggests that amateur astronomers looking at the sliver of darkness on the lunar surface that reaches to the moon's north pole may see bright flashes as meteoroids strike the lunar surface and kick up debris.
Dr. Jenniskens is taking part in an international campaign to observe the shower, using instruments the team will be running in a small jet flying out of Kiruna, Sweden. One goal is to see whether or not the 1900 event marked the comet's initial eruption. It's a blink-and-you-miss-it opportunity. Earth won't encounter the 1900 stream again for another 40 years.
Meanwhile, students in Bishop, Calif., are taking a different tack. Under a NASA science-education program, they will be lofting a weather balloon with a low-light camera in hopes that the balloon will reach the stratosphere and the camera snaps photos of the meteoroids as they enter the atmosphere.
"I hope they catch some Draconid fireballs for us to analyze," NASA's Cooke says. "They could be the only ones we get."