Debris from Halley’s Comet gives birth to one of 2012’s best meteor showers.
By Michael E. Bakich
Prospects look good for the peak of this year’s Orionid meteor shower, which occurs the night of October 20/21. Streaking swiftly across the sky, tiny bits of rock and metal burn up as meteors. Although Earth constantly sweeps up interplanetary dust, our planet runs through a slightly denser trail this month. Astronomers call this event the Orionid meteor shower because all of the meteors appear to radiate from the constellation Orion.
According to Astronomy magazine senior editor Richard Talcott, conditions should be good this year. “Although a waxing crescent Moon will share the sky with the Orionids before midnight, people will be looking away from it. The Moon shouldn’t cut the number of visible meteors by more than 20 percent.”
The radiant — the point in the sky where all the meteor trails trace back to — lies in northeastern Orion the Hunter, where that constellation borders Gemini the Twins. The Orionids’ radiant rises before midnight and stands high in the south by 4 a.m. local daylight time, a full two hours before dawn. This year, viewing conditions are favorable. At the shower’s peak, the waxing crescent Moon sets well before the prime observing hours after midnight.
Rates can reach 30 meteors per hour, and occasionally more. The predawn hours offer the best viewing because that’s when your location will face Earth’s direction of travel. Essentially, after midnight Earth will be running into the meteors.
The shower remains active all month, beginning October 2 and ending November 7. Meteor rates start and end with a trickle, but they achieve a substantial peak October 20/21. (The 1993 and 1998 Orionid showers showed higher rates three to four days earlier, so it’s worth watching the shower before its predicted maximum.)
At 148,000 mph (238,000 km/h), Orionid meteors are the second-fastest of any annual shower. Only the Leonids of November hit our atmosphere faster, at 159,000 mph (256,000 km/h).
The Orionid meteor shower is one of two that derive from Comet Halley’s debris. The other is the Eta Aquarid shower, which peaks in May.