Skywatch Line for Wednesday and Thursday, November 27 and 28, 2024, written by Alan French

This is Dudley Observatory’s Skywatch Line for Wednesday and Thursday, November 27 and 28, 2024, written by Alan French.

The Sun rises at 7:02 A.M. on Wednesday and sets at 4:24 P.M. On Thursday it rises at 7:03 and sets at 4:23. This Thursday has 12 minutes less daylight than last Thursday. In November we lose just over an hour of daylight.

The Moon reached last quarter this past Friday and is headed toward new. On Thursday at 5:30 A.M. a slender, old Moon will sit 10 degrees above the southeastern horizon. Just over 7% of the Moon’s visible face will be in sunlight. Note that the rest of the Moon is faintly illuminated. This is earthshine, light from a nearly full Earth in the lunar sky. By 6 A.M. the Moon will be 14 degrees high and morning twilight will reduce the apparent brightness of the earthshine. The slender crescent, however, is a pretty sight against the early twilight skies. The Moon will reach new this coming Sunday.

At 8:00 P.M. brilliant Jupiter, at magnitude -2.8, dominates the eastern sky, lying 32 degrees above the horizon. As I often mention, Jupiter’s four largest and brightest moons are easily seen in any modest telescope. They may also be spotted in a steady supported binocular when well away from the planet.
From our vantage point the four moons appear to shuttle back and forth, sometimes crossing in front of Jupiter and sometimes passing behind the planet, and always appearing roughly in a line. Spotting scopes designed for birding and nature study produce a correct view, a view that with correspond to the description here. Astronomical telescopes often produce a reversed or inverted orientation, so the view will differ from the description. Look for where the most moons appear to determine the orientation you see.

At 8:00 P.M. on Wednesday, Io, Europa, and Callisto, will be to the lower left (east) of the planet, with Io closest and Callisto farthest away. Ganymede will be on the opposite side (west) of the planet, closer to it than Io.

At 8 P.M. on Thursday their orientation will be different. Io will be the only moon to the upper right of the planet, while Ganymede and Callisto will be to the lower left, with Callisto still the farthest away. You may have a tough time spotting Europa, to the lower left and just off the planet. It is just about to begin a transit, and will be begin to move across the face of Jupiter at 8:04 P.M. Depending on your telescope and the steadiness of our atmosphere, you may be able to see Europa as it moves in front of Jupiter, but it can be challenging, and depends on the contrast between the moon and the part of Jupiter it is crossing. It is usually easier to spot when it is first moving in front of the planet or just before it moves off than when it is farther from a limb.

The moons also cast shadows on Jupiter’s cloud tops. Europa’s shadow moved onto Jupiter’s face earlier, at 7:35 P.M. You can go out sooner and watch it move onto the planet, or look for it to the west (right) of Europa at 8 P.M. The moon’s shadows appear as small, black spots, and are easier to spot than the moons themselves in front of Jupiter.