Fri, 19 Dec 2008 11:10 UTC
So, get out your 2009 calendar and put a big circle around Saturday morning, Jan. 3.
That's the expected peak date for the Quadrantids, a notoriously unpredictable meteor display. In 2009, peak activity is due to occur in the pre-dawn hours of Jan. 3 and will strongly favor western North America. If the "Quads" reach their full potential, observers blessed with clear, dark skies could be averaging one or two meteor sightings per minute in the hour or two prior to the break of dawn.
The Quadrantid (pronounced KWA-dran-tid) meteors provides one of the most intense annual meteor displays, with a brief, sharp maximum lasting but a few hours. Adolphe Quetelet of Brussels Observatory discovered the shower in the 1830's, and shortly afterward it was noted by several other astronomers in Europe and America.
The meteors are named after the obsolete constellation Quadrans Muralis the Mural or Wall Quadrant (an astronomical instrument), depicted in some 19th-century star atlases roughly midway between the end of the handle of the Big Dipper and the quadrilateral of stars marking the head of the constellation Draco. (The International Astronomical Union phased out Quadrans Muralis in 1922.)
Usually difficult to see
Unfortunately, many factors combine to make the peak of this display difficult to observe on a regular basis.
* Peak intensity is exceedingly sharp: meteor rates exceed one-half of their highest value for only about 8 hours (compared to two days for the August Perseids). This means that the stream of particles that produce this shower is a narrow one - apparently derived within the last 500-years from a small comet. The parentage of the Quadrantids had long been a mystery. Then Dr. Peter Jenniskens, an astronomer at the SETI Institute in Mountain View, Calif., noticed that the orbit of 2003 EH1 - a small asteroid discovered in March 2003 - ''falls snug in the shower.'' He believes that this 1.2 mi. (2 km.) chunk of rock is the source of the Quadrantids; possibly this asteroid is the burnt out core of the lost comet C/1490 Y1.
* As viewed from mid-northern latitudes, we have to get up before dawn to see the Quadrantids at their best. This is because the radiant - that part of the sky from where the meteors to emanate - is down low on the northern horizon until about midnight, rising slowly higher as the night progresses. The growing light of dawn ends meteor observing usually by around 7 a.m. So, if the "Quads" are to be seen at all, some part of that 8-hour active period must fall between 2 and 7 a.m.
* In one out of every three years, bright moonlight spoils the view.
* Over northern latitudes, early January often sees inclement/unsettled weather.
It is not surprising then, that the Quadrantids are not as well-observed as some of the other annual meteor showers, but 2009 could be an exception.
Excellent prospects in 2009
According to the International Meteor Organization, maximum activity this year is expected on 4:50 a.m. Pacific Standard Time on Jan. 3. For those across the western half of the United States and Canada, the radiant will soar high in the eastern sky just prior to the onset of morning twilight. Over the eastern United States and Canada, the spike of activity is predicted to come after sunrise.
Quadrantid meteors are described as bright and bluish with long silvery trains. Some years produce a mere handful, but for favorably placed observers, an excellent meteor display may be in the offing; at greatest activity, Quadrantid rates will likely range from 30 to 60 per hour for eastern parts of the U.S. and Canada, to perhaps 60 to 120 per hour for the western United States and Canada. For those in Europe, the shower's sharp peak will likely come long after sunrise. Nonetheless, hourly rates of perhaps 15 to 30 may still be seen.
As far as the moon is concerned, it will not be a factor at all this year. It's a waxing crescent, two days from first quarter phase and will have set around 11 p.m. local time on Friday, Jan. 2, leaving the rest of the night dark for meteor watching.