The legendary celestial hunter Orion lends his name to a modest but noteworthy meteor shower that peaks this week in predawn darkness.
While the Orionid shower runs from about Oct. 4 to Nov. 14, the heavenly show is most robust on Friday and Saturday morning, when the greatest number of meteors will slip into Earth’s atmosphere.
During the peak, 10 to 20 Orionids per hour should be visible. The Orionids are significant because although they are named for the Greek hero Orion, they are actually rock and ice shed from what may be the only cosmic snowball of frozen gas, rock and ice to gain widespread notoriety — Halley’s Comet.
And they are viewable twice each year. .
In May, the Earth also runs through the detritus of Halley’s Comet, creating the Eta Aquariid meteor shower.
“Over the ages, Halley’s Comet has shed bits and particles, and when we go through the streams, we get a meteor shower,” said Alan MacRobert, senior editor of Sky and Telescope magazine. “This is the only well-recognized semi-major shower that we do twice a year.”
Halley’s Comet was discovered by Edmund Halley in 1705, but is believed to have been recognized for millennia. NASA says the comet is featured in the Bayeux tapestry — an embroidered cloth that depicts the Battle of Hastings in 1066.
The comet returns every 72 years and was last seen from Earth in 1986. It won’t come again until 2061.
“It’s the first comet astronomers figured out was returning over and over again,” MacRobert said. “In many of its returns, it is large and bright and attracts a lot of attention.”
Orion is the namesake for the Orionids because they appear to radiate from north of Betelgeuse, one of the constellation’s most well-known stars. You don’t have to stare at Orion to see a meteor; they will be visible in all parts of the sky.
This year the peak of the Orionids will be overshadowed somewhat by the bright light of the waning gibbous moon.
But the skies should be mostly clear Friday morning, with the National Weather Service in Miami forecasting minimal sky cover and only a 10 percent chance of rain. Saturday morning will have more clouds getting in the way of viewing the Orionids, but still only a 10 percent chance of rain.
Deborah Byrd, editor in chief at the astronomy website Earth and Sky, said that while Orionid meteors may not be as plentiful as other showers, they can be surprisingly bright.
“Particles shed by the comet slam into our upper atmosphere where they vaporize at some 100 kilometers — 60 miles — above the Earth’s surface,” Byrd wrote in her astronomy blog. “Maybe half of the Orionid meteors leave persistent trains — ionized gas trails that last for a few seconds after the meteor itself is gone.”
MacRobert cautioned that people shouldn’t expect a fireworks show out of the Orionids.
“It’s not that major of a shower and this year there is moonlight, which will tend to wipe out all but the very brightest meteors,” he said. “So be very patient, lie back in a lawn chair and keep the moon out your vision.”
ALL ABOUT ORIONIDS
Comet of origin: 1P/Halley
Radiant: Just to the north of constellation Orion’s bright star Betelgeuse
Active: Oct. 4-Nov. 14
Peak activity: Oct. 21-22
Peak activity meteor count: 20 meteors per hour
Meteor velocity: 41 miles (66 kilometers) per second
Notes: The Orionids, formed from the debris of Halley’s comet, are known for being bright and quick.