Meteors past and future
Posted: Tuesday, August 14, 2007 9:00 PM by Alan Boyle
Submitted by Peter Orvick |
A Perseid streak stands out amid the stars in a picture taken from rural Minnesota.
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Now that the fireworks have settled down, skywatchers say the weekend's Perseid meteor shower performed about as expected - with fantastic displays separated by not-so-fantastic delays. "Seemingly interminable five- to 10-minute gaps ... followed by five meteors within 60 seconds," Bill Godley reported on the Meteorobs discussion forum. That roughly matches my own assessment, based on my outings early Sunday and Monday.
An even more elusive prize awaits: the Aurigids, which could outshine the Perseids - but only for a brief interval, in a particular area of the country, under special conditions. Take a look at some of the snapshots taken during recent meteor sightings, and get some special tips for the finicky fireworks ahead.
The meteoric streak above is a detail taken from a wider-angle photograph that Peter Orvick sent in response to our FirstPerson plea for pictures. "This is a picture of one of the Perseid meteors in the western sky in rural Minnesota," he wrote. "In the lower right-hand corner we just managed to catch one next going along the Milky Way."
Eugenio Bigornia sent in a similar snapshot from Alaska's Excursion Inlet. "I had given up, thinking it just takes dumb luck to get a meteor picture, so I just pointed my camera to the Big Dipper ... Not sure if it is a meteorite or a plane, but I think it is a nice shot with the Dipper and streak in the same frame."
Submitted by Melanie Reterrer |
Strange-looking sky phenomena punctuate a picture
of the sun's rays breaking over the horizon in Hawaii.
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The "shooting stars" in Melanie Retterer's picture at right probably aren't Perseids. In fact, I'm not sure what they are. But they do make for an interesting sunrise snapshot, taken on July 20 from the top of Haleakala on Maui.
Our FirstPerson meteor watch was a fair first effort, but for the cream of the celestial crop, you simply have to feast your eyes on the gallery at SpaceWeather.com. For years, the Web site has served up gobs of delicious pictures of meteors, auroral displays, noctilucent clouds and other sky phenomena.
When it comes to seeing this year's Perseids, Peter Jenniskens, a meteor researcher at the SETI Institute, had one of the best seats in the house: a seat aboard a NASA plane that made detailed research observations from an altitude of 45,000 feet.
"On the plane, of course, we see four or five times more meteors than we see on the ground," Jenniskens told me today. "Sometimes we see two or three at the same time. It was really a very nice shower to look at."
Jenniskens said the statistics for the Perseids pretty much matched the predictions, rising to a rate of around 86 meteors per hour at 6 a.m. ET Monday. He agreed that meteors can get a bit bursty - with appreciable gaps between sightings. Sometimes that's just a function of normal statistical distribution, but sometimes it indicates that larger pieces of debris have broken up into smaller pieces that re-enter the atmosphere at nearly the same time.
"If you see meteors move in the sky as pairs, then there's a bigger likelihood that a meteoroid broke into pieces," he told me.
For Jenniskens, the Perseid flight was just a practice outing for the Aurigids. Because Earth is passing through what's thought to be a particularly rich section of cometary debris this year, the Aurigids are expected to put on a brief, intense show at about 7:36 a.m. ET Sept. 1. That's a terrible time for East Coast observers, but it's not a bad time on the West Coast, where it will be 4:36 a.m.
"There will be really nothing two hours before the event, and then if you start watching around, say, 4 o'clock in the morning in California ... suddenly you'll see meteors, and gradually the rate will go up until the peak, about 4:36, and then it will go down again," Jenniskens said. "Then, after a half-hour or so, it will be over."
At the peak, a ground-based observer who has ideal viewing conditions could see two or three meteors per minute, he said. "It's like watering a distant flower with a garden hose, and you just hit the flower very briefly," Jenniskens explained. "That's a phenomenon that's extremely rare. We're very interested in this type of meteors."
That's why Jenniskens is keen on having regular folks go out and try photographing the Aurigids as they fall.
"This is a great way to get people involved," he said. "This is a very important little piece of science - that is, what is the biggest piece that made it out into the dust trail? We want to know if there are fireballs in the shower. Will somebody catch a fireball? ... You have to be lucky, but with this distributed-observing idea, somebody out there will be lucky to catch one."
Even if you're just in it for a good time, watching the Aurigids won't be quite as easy as watching the Perseids. You'll have to find clear skies, far away from city lights, of course - and the tips I passed along last weekend would still apply. But you'll also have to cope with the glare of a nearly full moon - an extra distraction that didn't enter into the picture for the Perseids.
"Put the moon behind an obstruction, like a telephone pole," Jenniskens advised. If the moon is blocked by a pole, or a building, that takes the direct glare out of your eyes. You'll also want to be facing east, not only to avoid the moon in western skies but also to have the meteor shower's radiant in sight. Aurigid meteors appear to emanate from a point in the constellation Auriga, but they can appear in any section of the sky.
Stay tuned for much more about the Aurigids in the weeks ahead - and if you do happen to snap an awesome Aurigid snapshot, feel free to send it our way using the FirstPerson page for sky sightings.
