When skywatchers think of meteor showers in December, they immediately think of the Geminids, which over the years have evolved into the most prolific and reliable of the dozen or so annual meteor displays that occur. And yet, there is also another notable meteor shower that occurs during December that, in contrast, hardly gets much notice at all: The December Ursids. The peak of this meteor display usually occurs during the overnight hours of Dec. 21-22.
The Ursids are so named because they appear to fan out from the vicinity of the bright orange star Kochabin the constellation of 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 Polaristhe North Star.
Where to spot Ursids
The fact that Kochab is positioned so near the north pole of the sky means that it 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 you can look for these faint, medium-speed meteors all through the night if you care to. The news is good at least so far as trying to catch of view of them this year, since the new moon is on Dec. 19, assuring dark skies.
These meteors are best seen during the last dark hour before dawn, when the radiant lies highest above the horizon in a dark sky. On the morning of maximum, hourly rates of between 5-10 Ursids may be seen. Plunging through the Earth’s atmosphere at 22 miles (35 km) per second, the Ursids produce mostly medium-speed meteors. Very little activity will be seen away from the night of maximum activity.
Historical outbursts
Indeed, the Ursids are a very poorly-observed Northern Hemisphere shower which has produced at least two major outbursts in the past 70 years, in 1945 and 1986. Some events could have been missed due to weather conditions. Several lesser rate enhancements have been reported from 2006 to 2008, and in 2011, 2014, 2015, 2017 and 2020, which might have been influenced by the relative proximity of the shower’s parent comet, 8P/Tuttlewhich circles the sun in a 13.6-year orbit and most recently swept past the sun in August 2021. And for some still unexplained reason, many Ursid peaks have occurred when comet Tuttle was not sweeping through the inner solar systembut rather at the far end of its orbit (aphelion), as far away from the sun as it can ge,t indicating that predictions are difficult.
Enhanced activity?
No unusually strong activity has been forecasted for 2025. However, a Dutch American meteor calculator, Peter Jenniskenslists an encounter with a dense filament of meteoric material on Dec. 22, at 12:39 a.m. EST. An hourly rate of 25 listed by Jenniskens is similar to values indicated by him for the 2021—24 returns, although no such enhancements were reported by observers in those years. French meteor expert Jérémie Vaubaillon has performed calculations using computer simulations that show that the densest section of the stream is in the vicinity of the Earth on Dec. 22 at around 5:00 a.m. EST, but with no pronounced peak.
Still, if you’re up before dawn breaks that morning, and if your skies are clear, you might want to step outside and check the northern sky. December’s nearly new moon gives a perfect chance to end the year on a positive note, if skies are clear enough to see what the Ursids may do this time.
Joe Rao serves as an instructor and guest lecturer at New York’s Hayden Planetarium. He writes about astronomy for Natural History magazine, Sky and Telescope and other publications.
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