Skywatch Line for Friday, December 13, through Sunday, December 15, written by Sam Salem
This is Dudley Observatory’s Skywatch Line for Friday, December 13, through Sunday, December 15, written by Sam Salem.
On Friday, Sun rises at 7:18am and sets at 4:22pm; Moon sets at 5:27am and rises at 2:37pm.
On Friday evening, the almost full Moon will sit between the planet Jupiter and Capella, the brightest star in the constellation of Auriga the Charioteer. Near Jupiter lies the orange star Aldebaran, the fiery eye of the constellation of Taurus the Bull. Look for the Pleiades star cluster nearby. They’ll rise shortly after sunset and be visible through dawn. Later in the evening, this whole arrangement will climb higher and rotate clockwise. About an hour before midnight, Pleiades will be directly right of the Moon, and Jupiter and Aldebaran will both be lower left of it.
Full Moon occurs at 4:02am Sunday morning. The full Moon of the Christmas season rides higher across the sky at midnight than at any other time of year. December is the month of the solstice, when the Sun is farthest south in the sky. This is when the full Moon is farthest north, opposite to the Sun.
Venus, magnitude –4.3 in the constellation of Capricornus, shines high in the southwest in evening twilight. It now remains up for nearly two hours after dark before setting. In a telescope Venus is gibbous, 63% sunlit, and 19 arcseconds from pole to pole.
Mars, magnitude –0.7 in Cancer, rises in the east-northeast around 8pm. It’s near its eastern stationary point, pre-opposition. It still forms the right angle of a rough right triangle with Castor and Pollux above it and Procyon to its right. Mars is 50° east along the ecliptic from brighter Jupiter. Mars remains 2° or 3° above M44, the Beehive star cluster, when seen in the east in late evening. Mars has enlarged to 12 arcseconds in apparent diameter.
Jupiter is just past its December 7th opposition, shining at magnitude –2.8 in Taurus. Spot it fairly low in the east-northeast as twilight fades. Jupiter is very high toward the southeast or south after 9pm. It’s 48 arcseconds wide in a telescope.
Saturn, magnitude +1.0 in Aquarius, glows highest in the south soon after dark. Saturn is now 40° east of Venus along the ecliptic.
On Friday evening, Saturn’s two largest moons, Titan and Rhea, will be close to each other, forming a telescopic “double star”, 7 arcseconds apart as they pass each other. Their minimum separation will come around 5:59pm, just after dark. Rhea will be south of brighter Titan. Watch them pulling apart for the rest of the evening. Titan and Rhea are magnitudes 8.5 and 10.0, respectively.
The Geminid meteor shower should be at its peak late Saturday night. The full moonlight will hide many of its meteors, leaving only the brightest ones to shine through. In the evening the meteors will be fewer still, but those that do appear will be long, Earth-grazers skimming far across the top of the atmosphere.