When skywatchers think of meteor showers during the month of December, they immediately think of the Geminids, the most prolific and reliable of the dozen or so annual meteor displays.
And yet, there is also another notable December meteor shower that, by comparison, hardly gets much notice at all — the Ursids. This year, the peak of this meteor display is due in the wee hours of Sunday morning (Dec. 22).
The Ursids got their name because they appear to fan out from the vicinity of the bright orange star Kochab, in the constellation Ursa Minor, the Little Bear. Kochab is the brighter of the two outer stars in the bowl of the Little Dipper (the other being Pherkad), which seem to march in a circle like sentries around Polaris, the North Star. [See spectacular photos taken by skywatchers this month]
If you can't catch the Ursids in person, you can watch the meteor shower in a live webcast hosted by the online Slooh Space Camera. You can watch the Ursid meteor shower webcast Saturday on SPACE.com via Slooh.
These meteors are also sometimes called the "Umids," in an attempt to make clear that their radiant is in Ursa Minor, not Ursa Major.
The fact that Kochab is positioned so near to the north pole of the sky means that it almost never sets for most viewers in the Northern Hemisphere. And since the Ursids seem to fan out from this particular region of the sky, it means that observers can look for these faint, medium-speed meteors all through the night.
The fact that the shower reaches its peak on the night of Dec. 21 to 22 as the moon is in its waning gibbous phases at first seems like bad news for viewing the shower. The moon will rise soon after 8:30 p.m. local time, lighting up the sky through Saturday night and into the predawn hours of Sunday morning.
However, as was the case with this year’s Geminids, there’s a “window of darkness” where the moon will not pose any interference. With the Geminids you needed to be out during the inconvenient morning hours between moonset and the break of dawn. But in the case of the Ursids, the time to watch this year will be on Saturday evening, after evening twilight ends and before the moon rises. Stargazers will have about 2.5 hours of dark skies for meteor viewing. So this return of the Ursids is not totally unfavorable.
This is indeed a fortunate circumstance because the Ursids "badly need observing," according to the British Astronomical Association.
That observers have neglected the Ursids is unsurprising, however. Everything about them is wintry. They usually coincide with the winter solstice, and are best seen by polar bears since they come from near the celestial North Pole.
In contrast to the Geminids, which can produce up to 120 meteors per hour, the usual Ursid rate is but a fraction of that. Generally speaking, they produce about 12 per hour at their peak.
These meteors are actually the dusty debris shed by the periodic comet 8P/Tuttle, which circles the sun in a 13.6-year orbit and was last seen in early 2008.
On occasion, the Earth has interacted with a dense, narrow stream of particles shed by this comet, which historically caused brief outbursts of Ursid meteors numbering in the dozens per hour. Counts reached 30 per hour in 2000. Unfortunately, no such interaction is expected this year.
Still, you never know …
Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmer's Almanac and other publications, and he is also an on-camera meteorologist for News 12 Westchester, N.Y.Follow us @Spacedotcom, Facebookand Google+. Original article on SPACE.com.
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Joe Rao is Space.com's skywatching columnist, as well as a veteran meteorologist and eclipse chaser who also serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for Natural History magazine, the Farmers' Almanac and other publications. Joe is an 8-time Emmy-nominated meteorologist who served the Putnam Valley region of New York for over 21 years. You can find him on Twitter and YouTube tracking lunar and solar eclipses, meteor showers and more. To find out Joe's latest project, visit him on Twitter.