Skywatch Line for Friday, December 20, through Sunday, December 22, written by Sam Salem
This is Dudley Observatory’s Skywatch Line for Friday, December 20, through Sunday, December 22, written by Sam Salem.
On Friday, Sun rises at 7:22am and sets at 4:24pm; Moon sets at 11:10am and rises at 10:08pm.
On Friday morning, the waning gibbous Moon will float near Regulus, the brightest star of Leo the Lion. Regulus looks like the dot at the bottom of a question-mark-shaped pattern of stars called the Sickle. Look for them a few hours before dawn.
This Saturday is the shortest day of the year in the Northern Hemisphere. The solstice occurs at 4:20am, when the Sun reaches its farthest southern declination and begins its six-month return northward.
Last-quarter Moon occurs at 5:18pm on Sunday. The Moon rises around midnight, under the hind feet of Leo. It’ll rise after midnight and set around noon. Look for it high in the sky before dawn.
Mercury is emerging to become an easy sight in early dawn. Look for it low in the east-southeast, about 40 minutes before sunrise. It brightens to magnitude –0.2 on Saturday morning.
Venus, magnitude –4.3, shines high in the southwest in evening twilight, crossing central Capricornus. It’s now high enough to remain up for two hours after dark before setting. In a telescope Venus is slightly gibbous, about 61% sunlit, and 19 or 20 arcseconds from pole to pole.
Mars, magnitude –0.9 in the constellation of Cancer, rises in the east-northeast by about 8pm. It’s just past its pre-opposition stationary point. It still forms the right angle of a right triangle with Castor and Pollux above it and Procyon to its right. Mars remains 50° east along the ecliptic from brighter Jupiter. Once Mars is well up, use binoculars to find M44, the Beehive star cluster, 2° or 3° below it. Mars shows best in a telescope when very high toward the southeast or south by midnight. It has enlarged to 12 arcseconds in apparent diameter.
Jupiter, two weeks past its opposition, shines at a bright magnitude –2.8 in Taurus. Spot it climbing in the east-northeast as twilight fades. As dusk deepens, watch for Aldebaran and slightly fainter El Nath to come into view to its right and left. Jupiter is at its telescopic best when very high toward the southeast or south by 9pm. It’s still 48 arcseconds wide.
Saturn, magnitude +1.0 in Aquarius, glows high in the south-southwest after dark. Saturn is now about 33° east of Venus along the ecliptic.