Earth To Experience Draconid Meteor Storm
By Mark Dunphy - Sat Oct 08, 9:10 am
Earth is scheduled to plow through a stream of dust from Comet 21P/Giacobini-Zinner on Saturday (08 October), and the result could be an outburst of Draconid meteors.
“We’re predicting as many as 750 meteors per hour,” says Bill Cooke of NASA’s Meteoroid Environment Office. “The timing of the shower favors observers in the Middle East, north Africa and parts of Europe.”
Every 6.6 years Comet Giacobini-Zinner swings through the inner solar system. With each visit, it lays down a narrow filament of dust, over time forming a network of filaments that Earth encounters every year in early October.
“Most years, we pass through gaps between filaments, maybe just grazing one or two as we go by,” says Cooke. “Occasionally, though, we hit one nearly head on–and the fireworks begin.”
2011 could be such a year. Forecasters at NASA and elsewhere agree that Earth is heading for three or more filaments on October 8th. Multiple encounters should produce a series of variable outbursts beginning around 1700 GMT (noon EDT) with the strongest activity between 2000 and 2200 GMT (3:00 pm – 5:00 pm EDT).
Forecasters aren’t sure how strong the display will be, mainly because the comet had a close encounter with Jupiter in the late 1880s. At that time, the giant planet’s gravitational pull altered the comet’s orbit and introduced some uncertainty into the location of filaments it has shed since then. Competing models place the filaments in slightly different spots; as a result, estimated meteor rates range from dozens to hundreds per hour.
“We’re hoping for an outburst for this year’s Draconid meteor shower on Saturday night,” said David Moore, Chairman of Astronomy Ireland. “Even with the Moon these meteors will be bright enough to be easily seen throughout the night. Maybe we might even get a meteor ‘storm’!”
One respected forecaster, Paul Wiegert of the University of Western Ontario, says the meteor rate could go as high as 1000 per hour — the definition of a meteor storm. It wouldn’t be the first time. Close encounters with dusty filaments produced storms of more than 10,000 Draconids per hour in 1933 and 1946 and lesser outbursts in 1985, 1998, and 2005.
Meteors from Comet Giacobini-Zinner stream out of the northern constellation Draco–hence their name. Draconids are among the slowest of all meteors, hitting the atmosphere at a relatively leisurely 20 km/s. The slow pace of Draconid meteors minimizes their danger to satellites and spacecraft and makes them visually distinctive.
“A Draconid gliding leisurely across the sky is a beautiful sight,” says Cooke.
Unfortunately, many of this year’s Draconids will go unseen. Draconids are faint to begin with, and this year they have to complete with an almost-full Moon. Lunar glare will reduce the number of meteors visible from Europe, Africa and the Middle East by 2- to 10-fold. The situation is even worse in North America where the shower occurs in broad daylight—completely obliterating the display.
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