By Elizabeth Weise, USA TODAY
A big meteor shower this weekend could produce as many as 60 falling stars an hour as the Earth passes through the trail of Halley's comet.
The yearly shower, called the Orionids, will have peak visibility over North America from midnight Saturday to just before dawn Sunday.
They'll still be visible the next night - midnight Sunday to dawn Monday - though the shower will be less strong, said Bill Cooke, head of NASA's Meteoroid Environment Office at the Marshall Space Flight Center in Huntsville, Ala.
The meteor shower probably wasn't the source of the large fireball seen Wednesday night over the San Francisco Bay area. The Chabot Space and Science Center in Oakland said that fireball was a car-sized piece of rock and metal from the asteroid belt.
Gerald McKeegan, an astronomer with the Chabot center, said he saw it as he was driving. "I looked up and there was this streaking ball of fire going across the sky," McKeegan said.
But it wasn't part of the Orionids. "Wrong time of the day and going in the wrong direction," he said.
The Orionid shower this weekend will begin just after midnight "wherever you are," Cooke said. The shooting stars will appear to fall from above the star Betelgeuse, the bright orange star marking the shoulder of the constellation Orion.
"The first-quarter moon will set around midnight, so its light will not interfere with the celestial show," said Rebecca Johnson, editor of StarDate magazine.
The annual Orionids meteor shower is caused by a swath of dust and rocks left behind hundreds of years ago by the renowned Halley's comet. Most years, the meteor shower produces about 20 to 25 shooting stars an hour that are visible, but Cooke expects this to be a good year with as many as 60 an hour that can be seen.
"The good news is we've already seen a fair number of bright Orionids on our meteor cameras, which might mean it will be a good year for the naked eye," Cooke said.
Halley's comet (the name rhymes with sally) orbits the sun every 75 to 76 years and won't be visible again from Earth for another 49 years. However, it has left a stream of tiny bits of dust and rocks - as the ice and rock it is composed of slowly melts. That stream hangs in space, and each year the Earth moves through it in mid-October.
"What we're seeing is those little bits burning up in the atmosphere," Cooke said. "They just kamikaze into the atmosphere and burn totally up." For those who "don't want to wait until 2061 to see Halley's comet, you can go out this weekend and look up" and see parts of it, he said.
To get the best view, find a place away from light sources so your eyes can adapt to the darkness. That can take up to 20 minutes. Lie on a blanket or reclining chair to get a full-sky view.
"If you can see all of the stars in the Little Dipper, you have good dark-adapted vision," Johnson said.