Skywatch Line for Wednesday and Thursday, November 8 and 9, 2023

This is Dudley Observatory’s Skywatch Line for Wednesday and Thursday, November 8 and 9, written by Alan French.

The Sun rises at 6:38 A.M. on Wednesday and sets at 4:39 P.M. On Thursday it rises at 6:39 and sets at 4:38. This Thursday has 17 ¼ minutes less daylight than last Thursday.

The Moon reached last quarter Sunday and is now headed toward new. The waning crescent Moon, 23% illuminated, rises in the east at 1:36 A.M. Wednesday morning. At 5:00 A.M. the Moon will be 34 degrees above the east southeastern horizon with brilliant Venus 10 ½ degrees below. This is just a preview for their much closer and more impressive and photogenic rendezvous Thursday morning.

The Moon rises in the east at 2:38 A.M. Thursday morning. Its visible face is just over 15% in sunlight. The Moon will be quickly followed by Venus, appearing above the horizon just 5 minutes later. By 3 A.M. the
Moon will be 3 degrees high  and Venus will be just ½ degree from the lunar limb.

By 4:00 A.M. the pair will be 13 ½ degrees high and Venus will be slightly closer to the Moon. At 5:00 A.M., just before the beginning of astronomical dawn, so the skies are still dark, the pair will be will be
24 degrees high. At 6:00 A.M. they will be higher, toward the southeast, and morning twilight will be encroaching. Morning twilight, however, may add to the beauty of their close encounter. Let’s hope the skies are clear!

While Venus dominates the morning sky, Jupiter shines brightly low in the east as the final remnants of evening twilight vanish at 6:18 P.M., when the gas giant is 20 degrees above the horizon. By 9:30 Jupiter will be 53 degrees about the southeast horizon.

As we have mentioned, the four largest and brightest moons of Jupiter are visible in almost any telescope, looking like stars to either side of the planet. It is fun and interesting to see how their apparent
positions change as they orbit Jupiter. From out vantage point, they appear to shuttle back and forth, moving from one side of the planet to the other and back. The innermost moon, Io, takes only 1.77 days to make one orbit. The outermost moon, Callisto, requires 16.7 days to complete an orbit. From our vantage point, the positions of the two inner moons, Io and Europa, change faster than the two outer moons, Ganymede and Callisto.

It you view Jupiter with any modest telescope at 7:00 and 9:30 P.M. you can see how the position of its moons change. At 7:00 P.M. on Wednesday Ganymede and Callisto will be to one side of Jupiter, both well away from the planet with Callisto farthest away. Io and Europa will be close to the opposite limb, with Io slightly closer. At 9:00 P.M. the positions of Io and Europa will have changed, with Europa now closer to Jupiter. On the opposite side, Ganymede will be slightly closer to Callisto.

At 7:00 P.M. Thursday all four moons will be on the same side of Jupiter, with Io and Europa having moved to the eastern side with Ganymede and Callisto. Io will be closest to Jupiter, followed by Europa
and Ganymede. Callisto will be well away from the planet, close to its most distant point. At 9:00 P.M Io will still be closest, but Ganymede will then be closer to Jupiter’s limb than Europa.