Skywatch Line for Wednesday and Thursday, December 11 and 12, 2024, written by Alan French
This is Dudley Observatory’s Skywatch Line for Wednesday and Thursday, December 11 and 12, 2024, written by Alan French.
The Sun rises at 7:16 A.M. on Wednesday and sets at 4:21 P.M. On Thursday it rises at 7:17 and sets at 4:21. This Thursday has just over 6 minutes less daylight than last Thursday.
The Moon was at first quarter last Sunday and is now headed toward full. At 6:30 P.M. on Wednesday a waxing gibbous Moon, its visible face 85% in sunlight, will be high in the east southeast. It will be due south and 63 degrees above the horizon at 8:41.
Thursday night at 6:30 will find the Moon, 92% sunlit, toward the east and 46 degrees above the horizon. Brilliant Jupiter will be 26-degrees to the lower left of the Moon. The Moon will be due south and 68-degrees above the horizon at 9:37 P.M.
At 7:30 P.M. Wednesday Jupiter is 37 degrees high in the east, almost 6 degrees higher than last Wednesday. Like last Wednesday, two of its Galilean moons will be on each side of the planet, visible in any modest telescope. The two to the east are Io and Europa, with Io closest, and to the west are Callisto and Ganymede, with Callisto closest. The closest moon to the planet is Io, to the east, and the pair to the west are closer to each other than the pair to the east. This will help distinguish the moons if your telescope happens to reverse the view.
Jupiter will be due south and highest at 11:26 P.M. Wednesday, when it will be 69 degrees above the horizon. This would be the best time to use a telescope to look for details in the planet’s atmosphere because the view is through a thinner layer of the Earth’s atmosphere. It is also a good time to spot Jupiter’s famous Great Red Spot (GRS) since it will be crossing the planet’s meridian.
Jupiter has two dark belts, one on either side of equator, the North and South Equatoria Belts, abbreviated NEB and SEB. The Great Red Spot pushes into the south side of the SEB.
On Thursday at 7:30 P.M. three moons will be to the east of Jupiter and one will be to the west, and the GRS will be close to the meridian, ideally placed for viewing.
The moons to the east, arranged in a rough triangle, will be Europa, Callisto, and Ganymede, with Europa closest to Jupiter and Ganymede farthest away. Io will be to the west.
When the skies are steady, especially through a larger aperture telescope, Jupiter’s cloud tops show a wealth of detail. Details become easier to spot with experience, time and experience behind the eyepiece is rewarded.