Selasa, 04 Oktober 2011

Draconid Meteors 8 oct. 2011

For the next few nights, Draco the Dragon will be spitting out “shooting stars,” also known as meteors. The Draconid shower is predicted to produce the greatest number of meteors on the night of October 8, 2011. Watch for them starting at nightfall. Unfortunately, the waxing gibbous moon will wipe many of these meteors from view, and oftentimes the hard-to-predict shower doesn’t offer much more than a handful of languid meteors per hour.

However, this shower produced major displays in 1933 and 1946 – with thousands of meteors per hour seen in those years – but since then has been so spotty that the tried-and-true Observer’s Handbook – source of so much wonderful sky info – lists a “?” for the rate of meteors expected at the peak of the Draconids. This year, however, some astronomers are calling for a Draconid meteor shower to burst into storm in 2011, with rates of 1,000 meteors per hour.

The forecast calls for the peak to occur between 17:00 and 18:00 Universal Time on October 8, 2001. If the prediction holds true, that means Europe, northern Africa and the Middle East will get to watch the Draconids at their peak. But keep in mind that meteor showers are notorious for defying predictions, either surpassing or falling shy of expectation, so you never know for sure. Even if the storm materializes, the bright moon will undoubtedy wash away many of these meteors. 

If you live at middle and far northern latitudes, though, it’s well worth a try. Unlike many major showers, the radiant for the Draconids is highest up at nightfall, so watch for these meteors as soon as darkness falls. 

Most meteor showers are named for the constellation from which the meteors radiate on the sky dome. The Draconids, however, are sometimes also called the Giacobinids, to honor the man who first sighted the comet that spawned this meteor shower. 

Michel Giacobini discovered this comet on December 20, 1900. Another sighting in 1913 added Zinner to the name of the comet, 21P Giacobini-Zinner. It is a periodic comet, which returns every 6 years and 4 months. Tracking this comet, and noting this October meteor shower, helped astronomers figure out how to predict meteor showers in 1915. The great Draconid/Giacobinid meteor storms occurred in 1933 and 1946. The comet returned in 1998 as well, and the Draconids picked up that year, but only to a rate of about 100 per hour.

Coming up in our lifetimes, in the year 2013 – approximately two years after the comet approaches perihelion (closest approach to the sun) – there might be another meteor storm around the time of this shower’s peak. Or there might not be.

There might be a meteor storm this year, in 2011. Perhaps the rates could go up to hundreds of meteors per hour in North America. Or we might see only a handful of meteors per hour. Under normal conditions, when astronomers speak of a meteor shower peaking, it is similar to a weather forecaster saying, “The heaviest rain/snow is predicted for such-and-such hour.” In other words, the prediction might not be precise, since nature is always unpredictable to a degree. But the rate of the meteors is higher during the peak of a meteor shower than on any other night.

For a taste of history related to this shower, go to the Astronomy Abstract Service from the Smithsonian and NASA and find a 1934 article called “The Meteors from Giacobini’s Comet” by C.C. Wylie. It is an account of the famed meteor storm of 1933.

If you want to try your luck, lie down on a reclining chair with your feet pointing northward. Find as much open sky as possible. How many Draconid meteors will be seen in the moonlit skies these next few evenings?
 by "environment clean generations"

Tidak ada komentar:

Posting Komentar