Skywatch Line for Wednesday and Thursday, December 4 and 5, 2024, written by Alan French

This is Dudley Observatory’s Skywatch Line for Wednesday and Thursday, December 4 and 5, 2024, written by Alan French.

The Sun rises at 7:10 A.M. on Wednesday and sets at 4:21 P.M. On Thursday it rises at 7:11 and sets at 4:21. This Thursday has 9 ¼ minutes less daylight than last Thursday. In November we lost just over an hour of daylight. As we approach the Winter Solstice, on December 21, the loss of daylight each day decreases. After the Winter Solstice, we begin to gain daylight.

The Moon was new early on Sunday, December 1, and is moving toward first quarter. After sunset on Wednesday a thin crescent Moon and brilliant Venus will be a lovely sight in the south southwest. Low in the sky, the pair will provide a nice photo opportunity with a good foreground choice.

At 5:00 P.M. Wednesday the 14% illuminated Moon will be 15 degrees above the horizon with Venus just over 3 degrees above it. By 5:30 the Moon will be 12 ½ degrees high and by 6:00, 9 degrees above the horizon. The Moon will set at 7:18 P.M., Venus at 7:29.

By Thursday night the Moon’s eastward motion against the starry background will have moved it well away from Venus, and the Moon will in the constellation Capricornus, 11 degrees to the upper left of the Venus. At 5 P.M. a 22% illuminated Moon is 22 ½ degrees high. It will set at 10:32 P.M. The Moon will reach first quarter on Sunday morning.

As Venus sets, brilliant Jupiter, at magnitude -2.8, dominates the eastern sky. Our solar system’s largest planet will be 32 degrees above the horizon.

At 7:30 P.M. on Wednesday the four Galilean moons of Jupiter are nicely placed for easy observation, all well away from the bright planet and two on either side. This would be a good time to try to spot them with a steadily supported or held binoculars. They will be easier, of course, with a spotting scope on a tripod or astronomical telescope on its mount.

To the east of Jupiter you will see Io, closest to the planet, and Europa, farthest away. To the west of Jupiter, Ganymede will be closest and Callisto farthest afield. This description will match what you see with binoculars or a spotting scope, but some astronomical telescopes will reverse the view. On Wednesday, it will be easy to see which is east and which is west in your telescope’s view. The two moons to the east will be in a line with Jupiter, the two moons to the west will not.

Thursday’s view at 7:30 P.M. will also feature two moons on each side of Jupiter. Europa and Ganymede will be to the east, with Ganymede farthest away, and Io and Callisto will be to the west, with Callisto considerably farther away. The pair farther from the planet is to the west, and the pair closer to the planet is to the east.