By Deborah Byrd in Tonight | December 20, 2017
onight – December 20, 2017 – we’re just one night away from the peak of the annual Ursid meteor shower. It always peaks near the time of the December solstice. In 2017, experts are calling for the peak on the night of the solstice itself, December 21 … best on the morning of December 22. The waxing crescent moon will set in the evening, providing moon-free viewing for the rest of the night. This shower favors more northerly latitudes in the Northern Hemisphere. The expected rate per hour is 5-10 meteors, but bursts of 100 or more meteors per hour have been observed at times, over the past century.
The chart at the top of the page shows the Big and Little Dippers around 1 a.m. when the Big Dipper is well up in the north-northeast. That’s about the time you’ll want to start watching the shower. Again, the peak is the morning of December 22, but tomorrow morning or Friday morning (December 21 or 23) might yield some meteors as well.
All meteors in annual showers have radiant points on our sky’s dome, and the showers take their names from the constellations in which the radiant points lie. The Little Dipper asterism is in the constellation Ursa Minor the Lesser Bear. Hence, the Ursid meteor shower.
If you trace the paths of the rather slow-moving Ursid meteors backward, they appear to come from the section of sky marked by the Little Dipper star Kochab .
Although the Little Dipper is circumpolar (out all night) at northerly latitudes, the star Kochab sits below Polaris, the North Star, at nightfall. Kochab (and all the Little Dipper stars) circle Polaris in a counterclockwise direction throughout the night, with this star reaching its high point for the night just before dawn. The higher the radiant climbs in your sky, the more meteors that you’re likely to see.
Read more: Start watching for Ursid meteors
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Ursid meteors radiate from near the star Kochab in the Little Dipper. The star Polaris is also part of the Little Dipper. Can’t find the Little Dipper? Use the Big Dipper! No matter what time of year you look, the two outer stars in the Big Dipper’s bowl always point to Polaris, which marks the end of the handle of the Little Dipper.
Bottom line: If you want to watch the Ursids, find a country location where you can camp out. Dress warmly! And plan to spend several hours reclining under a dark sky. The predawn hours are usually the most favorable, and, in 2017, the moon is out of the way.
Read more: Kochab and Pherkad guard the North Celestial Pole
Thanks to: http://earthsky.org