By Joe Rao
The Quadrantid meteor shower is due to reach maximum in Friday's predawn hours. The Quadrantids are notoriously unpredictable, but if any year promises a fine display, this could be it.
Indeed, this may end up being the best meteor shower of 2008. Let's hope not!
The Quadrantid (pronounced KWA-dran-tid) meteor shower provides one of the most intense annual meteor displays, with a brief, sharp maximum lasting but a few hours. The timing of peak activity favors Western Europe and eastern North America. Weather permitting, skywatchers in rural locations could see one or two shooting stars every minute during the peak.
Each year, many factors combine to make the peak of this display difficult to observe.
Peak intensity is exceedingly sharp: meteor rates exceed one-half of their highest value for only about eight 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.
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 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 eight-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-known as some of the other annual meteor showers, but 2008 may prove to be an unusual exception.
Exception this year
According to the International Meteor Organization, maximum activity this year is expected on Friday at 1:40 a.m. ET.
For those in the eastern United States, the radiant will be about one-quarter of the way up in the east-northeast sky. The farther to the north and east you go, the higher in the sky the radiant will be. To the south and west the radiant will be lower and the meteors will be fewer.
From Western Europe, the radiant will soar high in the east as the peak arrives just as morning twilight intervenes.
Quadrantid meteors are described as bright and bluish with long silvery trains. Some years produce a mere handful, but for favorably placed observers, this could be a shower to remember; at greatest activity, Quadrantid rates will likely range from 30 to 60 per hour for eastern parts of the U.S. and Canada, to 60 to 120 per hour for Western Europe.
Across central and western parts of North America, the shower's sharp peak will have already passed and meteor activity will be rapidly diminishing by the time the radiant has a chance to get very high in the northeastern sky. Nonetheless, hourly rates of perhaps 15 to 30 may still be seen.
The moon will be a waning crescent, not rising until after 4 a.m. and will add very little light to the sky.
History and mystery
Adolphe Quetelet of Brussels Observatory discovered the shower in the 1830s, 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.)
Meteor showers are generally caused by debris from comets. Most of the "shooting stars" result from bits the size of sand grains, which vaporize as they streak through Earth's atmosphere.
The parentage of the Quadrantids was long a mystery, however. Then 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-mile-wide (2 kilometers) chunk of rock is the source of the Quadrantids; possibly this asteroid is the burnt-out core of the lost comet C/1490 Y1. Whatever...