Skywatch Line for Wednesday and Thursday, December 25 and 26, 2024, written by Alan French

This is Dudley Observatory’s Skywatch Line for Wednesday and Thursday, December 25 and 26, 2024, written by Alan French.

The Sun rises at 7:25 A.M. on Wednesday and Thursday, and sets at 4:27 P.M. on both days. We are past the Winter Solstice, the Sun is moving north, although slowly, and Thursday gained just under 2 minutes of daylight compared to last Thursday. The pace of increase will gradually accelerate.

The twice-yearly change of clocks, springing ahead an hour on the second Sunday in May and falling back an hour on the first Sunday in November, tends to evoke complaints, and there are regular discussions about doing away with the change. The most recent legislation proposed in Congress made Daylight Saving Time year-round, meaning the clocks would be set ahead an hour and never fall back.

The country did this experiment before, a change inspired by the gas shortage in 1973. On December 14, 1973, Congress voted to put the country on year-round Daylight Saving Time (DST), a move supported by 79% of the people. President Richard Nixon signed the legislation the next day and permanent DST went into effect on January 6,1974, with the clocks moving ahead an hour.

If DST was in effect on Thursday, with the clocks ahead an hour, the Sun would not rise here now until 8:25 A.M. Farther north, where the now southern Sun travels a lower arc across the sky, sunrise would be even earlier. In Plattsbugh the Sun would rise at 8:30. Farther west, the Sun rises later. In Buffalo the sun would rise Thursday at 8:45. Grand Rapids, Michigan, father west, is still in the Eastern Time Zone, and sunrise would not be until 9:12.

After year-round DST went into effect in January, the late sunrises and extra morning darkness quickly became unpopular. They also proved dangerous to children on their way to school. Three months after finding 79% favoring DST, only 42% were found in favor. It was so unpopular, that in August, 1974, legislation was proposed to end year-round DST. It was passed by Congress in late September and signed into law by President Lyndon Johnson. Standard Time was restored on October 27.

The Moon reached third quarter Sunday and is now moving toward new. You can catch a waning crescent, old Moon in the morning sky before sunrise. At 6 A.M. Wednesday a 27% sunlit Moon will be 28 degrees above the south southeastern horizon. On Thursday at 6:00 A.M. it will be 20-degrees high, 19% in sunlight, and a little farther south. By Friday it will be in the southeast, 11 degrees high, and only 12% of the visible face will be in sunlight. The Moon will reach new Monday, December 30.

Venus continues to dominate the early evening sky, now just under 20-degrees above the southwestern horizon at 6:00 P.M. and at magnitude -4.3. Through a telescope Venus appears moderately gibbous, with 58% of its visible face in sunlight. On its faster, inner orbit, Venus is slowly catching up with Earth. It will reach inferior conjunction, passing roughly between Earth and the Sun, on March 22, 2025, our time.

At 6:00 P.M. you will also find bright Jupiter, magnitude -2.6, in the east southeast, 54-degrees above the horizon. On Wednesday at 6:00 P.M. any modest telescope will reveal Europa to the east of Jupiter, and Io, Ganymede, and Callisto to the west. Callisto, however, will be very close to the planet’s limb, just about to be occulted by Jupiter. Io will disappear behind the planet at 6:09. When the moon moves out from behind the planet, it will emerge into Jupiter’s shadow and be eclipsed. Io will emerge from eclipse, into sunlight, away from the planet’s western limb and become visible at 8:48 P.M.

On Thursday at 6:00 P.M. all four visible moons will be seen. Ganymede and Europa will be to the east, and Io and Callisto to the west. Again, Io, will be close to the western limb. This time, however, Io will be moving farther westward, having emerged from crossing in front of the planet, a transit, at 5:28 P.M. Ganymede, visible just to the west, emerged from eclipse at 5:39 P.M.