2000-Year-Old Meteors to Rain Down on August 31, 2007

The meteors that are about to rain down in the early morning of September 1 date from around 4 A.D., the latest calculations show.

2000-Year-Old Meteors to Rain Down on August 31, 2007

The meteors that are about to rain down in the early morning of September 1 date from around 4 A.D., the latest calculations show.

It is not often that we can tell when a shooting star was first released from a comet into space, to travel as a meteoroid in an orbit around the Sun, and finally collide with Earth's atmosphere to shine as a meteor for our enjoyment. Most meteors that sporadically flash across the sky on a dark moonless night date from anonymous times. Only in recent years have we learned to trace young meteor showers, just a few revolutions old, to their date of origin.

The oldest such shower, but only one revolution old, is due in the early morning of September 1, 2007. Our calculations indicate Earth is about to cross the dust trail of comet Kiess, a comet that takes some 2000 years to complete one orbit around the Sun. The trail is very narrow, so Earth will be hosed by meteoroids for only about an hour and a half. The meteoroids will approach from the direction of the constellation Auriga, the charioteer, in the north-eastern part of the sky, causing a meteor shower called the "Aurigids."

If you spot one of those meteors, you may be only the fourth person alive who is known to have seen this meteor shower. In recent times, the shower was spotted in 1994 by two observers and in 1986 by one observer.

If you are lucky enough to catch a picture of an Aurigid meteor using your digital camera, you will be the very first to do so.

Tips on how to observe meteors and where to report the results can be found at: http://aurigid.seti.org

The shower is visible from only part of the world. If you live in the western parts of the USA, Canada and Mexico, including Hawaii and Alaska, you might spot an Aurigid meteor. Plan to step out around 4 A.M. PDT in the early morning, warmly dressed with a blanket wrapped around your shoulders, away from city smog, with the Moon behind an obstruction, and with a wide view on the sky. Gaze up at the sky, waiting, and you may spot one of these elusive bits of matter that Comet Kiess lost 2000 years ago.

This is your only chance to see this shower; the dust trail is not going to hit again in our lifetime. It is also our best chance yet to test meteor shower prediction models and look for evidence of the crust that a comet is suspected to build up during the time it spends in the Oort cloud. Comets in shorter orbits have long lost this pristine crust.

Jon Giorgini of JPL/Caltech has identified observations of Comet Kiess when it returned in 1911. The orbit is now better determined than before and calculating backwards in time puts the comet near Earth's orbit in 4 A.D., give or take 40 years. It was at that time that the dust was released that we now see as meteors. The dust was ejected in wider orbits than the comet and took somewhat longer to return.

Jeremie Vaubaillon of Caltech calculated where the dust would end up at Earth's orbit on September 1, 2007, if it was ejected in 4 A.D. and he found that, indeed, the dust trail will be in Earth's path. The peak is expected at 11:33 UT, or 4:33 a.m. PDT, give or take 20 minutes.

From past Aurigid showers, we anticipate a shower of mostly -2 to +3 magnitude meteors with a peak Zenith Hourly Rate about 200 per hour during a 10-minute interval, with rates above 100 per hour for only 25 minutes. With a bright Moon in the sky, only 4 days past full, that translates to several tens of chances to make a wish on a meteor from around 4 A.D.

To increase our chances of catching these rare meteors, we will be observing the shower from two Gulfstream GV aircraft (flying at 45,000 ft) on a parallel flight path from Wisconsin, over the Bay Area in California, and on to the Pacific in the early morning of September 1. An international team of 24 researchers will have 21 windows to aim their cameras through. The cameras are of different types, some similar to your own digital camera and camcorder, others using technologies more familiar to cameras used on astronomical telescopes or those in night vision goggles. Near the horizon, we hope to see many more meteors than will be visible from the ground, but each of us will be glad if the shower actually shows.

You can participate in this research by making an effort to photograph or film the Aurigid meteors. Chances are that one of you, not us, will catch the brightest Aurigid out there. Even simple cameras can provide information about how the meteoroids break apart, as each image is composed of three different images: one in blue light, another in green, and one in red. Each color traces different aspects of the meteor's light.


Last Mod: 24 Ağustos 2007, 19:07
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