Skywatch Line for Friday, December 22, through Sunday, December 24, 2023

This is Dudley Observatory’s Skywatch Line for Friday, December 22, through Sunday, December 24, written by Sam Salem.

On Friday, Sun rises at 7:23am and sets at 4:25pm; Moon sets at 2:44 am and rises at 1:15 pm.

Jupiter shines to the Moon’s right at dusk on Friday and moves to its upper right later at night. On Saturday, the waxing gibbous Moon is about 5° to the right of the Pleiades in early evening. Binoculars help with the Pleiades through the moonlight. Watch the Moon draw closer to the Pleiades hour by hour, finally passing only about 2° south of them shortly before setting in the northwest around the first light of dawn Sunday morning.

On Sunday, the bright gibbous Moon moves to the lower left of the Pleiades in early evening. It forms a flattened, nearly isosceles triangle with the Pleiades above it and Aldebaran below.

Around 11 pm on Sunday night, the Moon shines just about as close to the zenith as you will ever see it, “casting luster of midday on objects below.” Your Moon shadow at that time will be the shortest you’ll ever see it. The Moon will do very nearly the same close zenith pass about an hour later each night for the next several nights.

The annual Ursid meteor shower runs from about December 13 to 24 every year. This low-key meteor shower, which always peaks around the solstice, is somewhat overlooked due to the holiday season. Its hourly rate is lower than that of the Geminids shower, which peaks over a week before. The Ursids’ peak is predicted on Saturday morning. The waxing gibbous Moon may interfere with the Ursids this year until the Moon sets about three hours before sunrise. Generally, the Ursids are a low-key affair, offering perhaps as many as five to 10 meteors per hour in a dark sky with no Moon. In rare instances, bursts of 100 or more meteors per hour have been observed.

8P/Tuttle is the comet responsible for the Ursids meteor shower. Pierre Mechain discovered it on January 9, 1790, from Paris, France. Comet 8P/Tuttle gets as close to the Sun as does the planet earth, then goes out as far as the orbit of Saturn. Its path is tilted to the earth’s orbit, and Earth intercepts the material as it descends from above our orbit.

Venus, at magnitude –4.1 in the constellation of Libra, shines as the bright “Morning Star” in the southeast before and during dawn. It’s not as high as it was a month or two ago. Venus rises above the east-southeast horizon about 1½ hours before dawn’s first light. Watch for it to come up three or four fists at arm’s length to the lower right of Arcturus, the brightest star twinkling high in the east.

Jupiter, at magnitude –2.7 in the constellation of Aries, is the bright white dot dominating the high southeast to south in the evening. It stands at its highest in the south around 8 pm. It has shrunk a little since opposition, but it’s still a good 46 arcseconds wide in a telescope.

Saturn, at magnitude +0.9 in the constellation of Aquarius, glows yellowish lower in the south-southwest just after dark. Fomalhaut, twinkles roughly two fists at arm’s length to Saturn’s lower left. Saturn declines toward the southwest as evening progresses and sets around 10 pm.