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Only now are we descending from the peak of the year for meteor enthusiasts: the Geminid meteor shower, which peaked at a prolific 60 to 120 meteors per hour on the night of December 13-14. But there is still one more meteor shower to consider before closing the book in 2020: the December Ursid meteor shower, which usually occurs during the night hours of December 21-22.
Ursids are so named because they appear to fan out from the vicinity of the bright orange star Kochab, in the constellation Ursa Minor, the bear. Kochab is the brightest of the two outer stars in the bowl of Ursa Minor (the other being Pherkad), which appear to circle like sentinels around Polaris, the North Star. But while the Geminids are at the top of most meteor watchers’ “must-see” lists, the Ursids are usually at the bottom, and generally receive little attention except for the most assiduous meteor watchers.
Related: How Meteor Showers Work (Infographic)
Often neglected
The fact that Kochab is so close to the north pole of the sky means that it hardly ever fixes for most viewers in the northern hemisphere. And since the Ursids seem to fan out from this particular region of the sky, it means you can search for these weak, medium-speed meteors all night long if you want. And this seems to be a reasonably good year for them, as the first quarter of the moon will set around midnight on its peak night, ensuring that the skies will be dark for the second half of the night.
These meteors are best seen during the last dark hour before sunrise, when the radiant is highest above the horizon in a dark sky. On peak morning, hourly rates of 5-10 ursids can be seen. Diving through Earth’s atmosphere at 22 miles (35 km) per second, the Ursids produce mostly medium-speed meteors. Very little activity will be seen outside of the busiest night.
Ursids are a very poorly observed rain from the northern hemisphere; That observers have neglected the Ursids is not surprising. Everything about them is wintry. They generally coincide with the winter solstice and are best seen by polar bears as they come from near the north celestial pole.
The parent comet of the rain, from which these meteoroids originate, appears to be 8P / Tuttle, which orbits the sun in a 13.6-year orbit and will return to the vicinity of the sun in August 2021. On occasion, the planet Earth has interacted with a dense, narrow stream of particles released by this comet, which has caused brief bursts of Ursid meteors that number in the dozens per hour, as in 1945 and 1986; others may have been lost due to widespread bad weather or simply because no one bothered to look. Several minor speed improvements have been reported between 2006 and 2008, which could have been influenced by the relative proximity of Tuttle’s comet. The slightly improved rates found in the video data in 2014 and 2015 indicate that trying to predict what this meteor swarm might do in any given year is difficult.
Improved activity in 2020?
Several highly regarded meteorite experts have examined the orbit of Comet Tuttle and suggested that Earth could find some ancient traces of dust thrown up by Comet 8P / Tuttle that could possibly enhance Ursid activity this year.
Esko Lyytinen and Peter Jenniskens predicted in the International Meteor Organization’s 2020 meteor shower calendar that material spewed by the comet in the years 815 and 829 (about 1,200 years ago) could interact with Earth between 12:27 and 1:10 am EST (0527 and 0610 GMT). And earlier in the evening, Japanese researchers Mikiya Sato suggests in that same paper that the combination of two even earlier ancient trails from 719 and 733 could affect our planet between 10:15 and 10:40 p.m. EST (0315 and 0340 GMT). December 21.
Unfortunately, all of this material has been in space for about 13 centuries and is likely to have been widely dispersed and is not likely to provide a large increase in the nominal rates of 5 to 10 per hour expected of Ursids.
Still, if your skies are clear, you may want to go outside and look at the northern sky. This could be a good excuse to try to end the year on a positive note.
Hey, you never know.
Joe Rao serves as an instructor and guest speaker at the Hayden Planetarium in New York. He writes about astronomy for Natural History magazine, Farmers’ Almanac, and other publications. Follow us on Twitter @Spacedotcom and on Facebook.
