Click on image for full size
Original animation by Windows to the Universe staff (Randy Russell). Images courtesy NASA/JPL.
Quadrantid Meteor Shower
The Quadrantid meteor shower is one of several major meteor showers that occur on roughly the same date each year. The Quadrantids "peak" (are at their greatest level of activity) in early January. In 2010, the Quadrantids peak at 1900 Universal Time on January 3rd. That's 4 PM Eastern time; so the early evening hours of January 3rd will be the best time for viewing the Quadrantids in 2010.
The meteors in a specific meteor shower all appear to fan out from a point in the sky, called the shower's "radiant". Meteor showers are named after the constellation in which their radiants are located; for example, the Orionid meteor shower has its radiant in the constellation Orion. So in what constellation does the radiant of the Quadrantids lie?
The Quadrantids are named after the constellation Quadrans Muralis... a constellation that no longer exists! Quadrans Muralis was a "modern" constellation that was invented in 1795 by French astronomer Joseph Jérôme de Lalande, who named it after an astronomical instrument used to measure the positions of stars. Lalande placed his new constellation between the traditional constellations Bootes and the tail of Ursa Major (the Big Dipper). A new meteor shower that hadn't previously been observed was discovered in the 1800s, and since its radiant was in Quadrans Muralis it was named the Quadrantids. However, in 1922 the International Astronomical Union (IAU) established the modern list of 88 official constellations. Quadrans Muralis was not on that list, and so the constellation "ceased to exist". However, the name of the meteor shower had been established, and it stuck... despite the demise of its namesake constellation.
Unlike some meteor showers which have been known of since antiquity, the Quadrantids were first observed in the 1820s and 1830s. They were recognized as an annually recurring shower in 1839. At first there were relatively few Quadrantids seen in any given year, but in 1864 a strong shower occurred with peak rates of 60 meteors per hour. This outburst brought attention to the Quadrantids. However, less is known about the shower than is the case for other major showers. Since the Quadrantids appear in January, winter storms often spoil viewing opportunities, and cold weather means that fewer observers have recorded this event over the years than is the case for other showers that happen at warmer times of the year. Also, the peak of activity of the Quadrantids spans a relatively short time period (sometimes just a few hours), further restricting viewing opportunities.
The fact that the Quadrantids weren't observed until modern times may indicate that the event that created this meteor shower happened quite recently. Most meteors in showers come from the debris trail left by a comet. The dust, which spews forth from the comet's nucleus each time it passes near the Sun, gradually spreads out over the entire orbit of the comet. If Earth's orbit happens to cross the comet's orbit, the swarm of debris scattered along the comet's orbit is visible to us as a meteor shower. Since the Earth crosses the comet's orbit at the same time each year, each meteor shower is predictably visible at the same time of year, year after year. Searches for the parent body that produced the Quadrantids were fruitless until 2003, when Peter Jenniskens identified the near-Earth asteroid 2003 EH1 as the likely source of the Quadrantid shower. Astronomers think that this "asteroid" may actually be the remains of an "extinct" comet that has lost all of its ices after repeated passes near the Sun. They further speculate that asteroid 2003 EH1 may be just a piece of a larger comet that broke apart and generated a swarm of meteoroids in the process. This event might have happened within the last 1,000 years, or possibly even the last 500 years... making the Quadrantids a young meteor shower indeed. Some astronomers think that asteroid 2003 EH1 might even be a piece of comet C1490 Y1, which was observed in China, Korea, and Japan between December 1490 and February 1491!
The number of meteors visible at the peak of the Quadrantid shower varies substantially from year to year. Sometimes the rate is as low as 20 meteors per hour, though the typical rate is over 100 per hour. In 1909, an unusually active Quadrantid shower produced roughly 200 meteors per hour. Most Quadrantids are fairly faint meteors that travel at moderate speeds (for meteors) of about 41 km/sec (nearly 92 thousand mph). Sometimes Quadrantids can be spotted as early as December 28th, and can linger until January 7th. However, as mentioned earlier, the shower's peak is usually quite brief and typically occurs around January 3rd or 4th. Unfortunately, 2010 may not be the best year for watching Quadrantids. The Moon will be just past its full phase on the 3rd, so bright moonlight may interfere with spotting dim meteors once the bright Moon rises.
