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December 20: Io and its shadow transit Jupiter
The winter solstice occurs today at 10:03 A.M. EST. This marks the beginning of astronomical winter in the Northern Hemisphere and astronomical summer in the Southern Hemisphere. (Note that meteorological winter began December 1st, so you may have already heard news outlets saying it is wintertime before this date.)
On the winter solstice, the Northern Hemisphere experiences its shortest duration of daylight. After this date, the Sun will begin to remain above the horizon for longer, although it may take a few days for sunrise and sunset times to change, depending on your location.
The solstice itself — at 10:03 A.M. EST — is the exact moment the Northern Hemisphere is tilted farthest from the Sun. On this date, the Sun makes its lowest arc through the Northern Hemisphere sky as well, while our star sits directly overhead at noon for those on the Tropic of Capricorn in the Southern Hemisphere.
Astronomical winter will last until the spring equinox, which will occur March 20, 2026, at 10:46 A.M. EDT.
Sunrise: 7:19 A.M.
Sunset: 4:38 P.M.
Moonrise: 8:54 A.M.
Moonset: 5:59 P.M.
Moon Phase: Waxing crescent (4%)
*Times for sunrise, sunset, moonrise, and moonset are given in local time from 40° N 90° W. The Moon’s illumination is given at 10 P.M. local time from the same location.
Tomorrow morning, December 22, offers a chance to catch the last major meteor shower of the year: the Ursids. This short-lived shower is active for only about a week and peaks this morning under dark, moonless skies.
Although the Ursids’ peak rate is just ⅒ that of the Geminids last week — meaning at its best, it will only produce about 10 meteors per hour — it’s still worth stepping outside before sunrise to see if you can catch a few shooting stars. In fact, the radiant in the north is visible all night for much of the Northern Hemisphere, meaning you can watch for meteors late on the 21st as well as again on the evening of the 22nd.
The Ursids’ radiant is located just off the cup of the Little Dipper. It is nearly 50° high in the north by 5 A.M. local time, to the upper right of the North Star, Polaris. If you can find the Big Dipper in the northern sky — upside-down early this morning — look beneath its cup to find the matching, smaller cup of the Little Dipper. These cups always appear to pour into each other as the stars wheel around the North Celestial Pole, anchored by Polaris.
