The Perseid meteor shower has come and gone, but that doesn't mean that there aren't any more good meteor displays to look forward to. In fact, another potentially good shower is just around the corner, scheduled to reach its peak during the early hours of Saturday, September 1st: the Aurigid meteors.
The Aurigids get their name from the constellation of Auriga, the Charioteer. The meteors appear to emanate from a spot in the sky near the bright yellowish star Capella in Auriga. The Aurigids, however, are rarely mentioned in most astronomy guidebooks because they are hardly worth mentioning in any given year.
Then why bother about a shower that almost nobody has heard of and that's due this year just days after a bright full moon?
Because in 2007, these unheralded Aurigids are this summer's wild card.
Unlike the steady and reliable Perseids,
little or no activity is usually seen from the Aurigids.
Yet, every once in a great while a short-lived outburst of
bright meteors has been reported from the Aurigid
shower. Peter Jenniskens of the SETI Institute's
Outburst in 2007?
Aurigid outbursts are very infrequent, having been definitively seen on only three occasions: in 1935, 1986 and 1994. There were very few witnesses on each occasion, because these sudden outbursts were totally unexpected.
But now, for the first time, an alert for an impending Aurigid outburst has been issued.
At the 26th General Assembly of the International
Astronomical Union Conference held last August in
The comet responsible for the Aurigids is well known: Comet Kiess, which last appeared in 1911. In carefully examining its movements, the meteor scientists have determined that prior to 1911, this comet previously swept passed the sun sometime around the year 82 BC (when Julius Caesar was alive). Jenniskens and Vaubaillon calculated that a trail of dust released by the comet at that 82 BC visit will run smack into Earth's path when our planet passes by on September 1.
Far-western states favored
On Saturday morning, September 1st, in the hour centered on about 11:37 UT, Earth should encounter the trail of dust released from Comet Kiess.
That moment (4:37 a.m. Pacific Daylight Time) favors the
far-western parts of the
Unfortunately, most of the rest of
Jenniskens and Vaubaillon are forecasting a ZHR (zenithal hourly rate the number of meteors seen by a single observer under a clear, dark sky with the meteors' emanation point directly overhead) of 200. Their outlook is very similar to Esko Lyytinen, who predicts a ZHR of 300, but with an added uncertainty of 1 to 3. Notes Lyytinen, "This would mean something between about 100 and 1,000. Let's hope this will be around 1,000!"
There is, however, a significant drawback: a bright gibbous moon will be lighting up the sky on the morning of the shower.
But because the Aurigids ram through our atmosphere at exceptionally high speeds of 41 miles per second (66 kps), and since these particles are predicted to be rather large, the display is expected to be rich in bright meteors, with many appearing as bright as the brightest stars and a few perhaps approaching or even rivaling Jupiter and Venus. "So," says Jenniskens, "the moon probably won't dim much of the display."
Probably the safest bet is to play it conservative and forecast a rate of perhaps only 20 to 30 per hour, which is what was observed during the three previous Aurigid outbursts. But if those meteors are as bright as the calculations suggest they will be, it could still be a memorable albeit brief show.
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