Every November, Earth crosses the orbit of comet Tempel-Tuttle - the comet itself appears in our skies only every 33 years - and the Leonids become visible as they enter the atmosphere traveling at speeds of more than 158,000 mph. Onlookers on the side of the planet facing the oncoming meteors get the best view, which also is affected by such factors as the size of the moon, cloud cover and city lights, according to AMS member Gary W. Kronk's Comets & Meteor Showers Web site at www.comets.amsmeteors.org.
"Everyone likes meteor showers," says Kevin Boles, president of the Morgan County Observatory Foundation in Berkeley Springs, W.Va.
He says meteor showers are popular because of their potential magnificence and extended duration. While meteor showers are typically best viewed between midnight and dawn, meteors can really be seen in the dark sky for days before and after predicted peak times, Boles says.
"Whenever you've got time, just get out and look up at the stars," he says.
The Leonid shower - so named because the shower's radiant point, from where the meteors seem to fan out, is within the constellation Leo - was expected to peak first on Thursday, Nov. 13, and again on Wednesday, Nov. 19. Scientists don't expect this year's Leonid shower to rival last year's show, but they do predict a brief but bright display of up to 50 meteors per hour to light up the skies at about 5:25 Universal Time (12:15 a.m. EST) on Nov. 19, according to NASA's Leonid Multi-Instrument Aircraft Campaign Web site at www.aio.arc.nasa.gov. Astrobiologist Peter Jenniskens of the SETI Institute's Center for the Study of Life in the Universe has dubbed the anticipated bright show, "The Fireball Shower."
(All meteor peak times are given in Universal Time, which is another way of describing Greenwich Mean Time (GMT). To convert UT to Eastern Standard Time, subtract five hours from UT from Oct. 31 to April 30 and four hours from UT from April 30 to Oct. 31, says Kim Youmans, visual observing program coordinator for the American Meteor Society.)
Peaking a few hours later Wednesday at about 17:28 UT (2:28 a.m. EST) and lasting up to 24 hours, skywatchers across much of North America might see up to 30 meteors per hour as the Earth passes within 33,000 miles of a dust trail shed by Tempel-Tuttle nearly 500 years ago, scientists predict.
The Geminid meteor shower is predicted to peak at 15:10 UT (10:10 a.m. EST) on Sunday, Dec 14. The only major shower clearly shown to be non-cometary, the Geminid shower shares an orbit with an asteroid that comes unusually close to the sun and passes through Earth's orbit, the American Meteor Society's Web site states.
The Geminids were first noted in 1862, and sightings gained speed in the 1870s as astronomers realized that a new annual shower had been discovered. Visual evidence of this shower indicates that activity persists from Dec. 6 to 19, but meteoric activity has been detected as early as Dec. 4 and as late as Dec. 29, according to the AMS.
To observe meteors, it's best to wait until after midnight, and choose a dark site as far from city lights as possible, Youmans says. Give your eyes time to adjust to the dark conditions. Recline, directing your gaze about 45 to 75 degrees above the horizon in the general direction of the shower radiant. The best portion of the sky to watch is usually an area about 25 to 45 degrees away from the radiant point. Most importantly, be patient and don't expect myriad meteors within a short period of time, Youmans adds.
The American Meteor Society offers many tips for observing meteor showers on the organization's Web site.