Skywatch Line for Monday and Tuesday, December 30 and 31, 2024, written by Alan French
This is Dudley Observatory’s Skywatch Line for Monday and Tuesday, December 30 and 31, 2024, written by Alan French.
The Sun sets at 4:32 P.M. and night falls at 6:14. Dawn begins at 5:44 AM and ends with the Sun rising at 7:24. This Tuesday has 3 ½ more minutes of daylight than last Tuesday.
The Moon reaches new late Monday afternoon and is too close to the Sun to see Monday evening. On Tuesday the young Moon will set just over 30 minutes after sunset. At 4:47 P.M., 15 minutes after sunset, with bright evening twilight, the slender, crescent Moon, just over 1% illuminated, will be just 2-degrees above the southwestern horizon. It will be a challenging target under the best conditions, requiring an excellent view southwest and clear skies near the horizon. Circumstances will improve as we move into January and the Moon moves toward first quarter, higher into the evening sky, and lingers longer after sunset. The Moon will reach first quarter on Monday, January 6.
Venus continues to dominate the early evening sky, shining at magnitude -4.4 in the southwest. At 5 P.M. it is 28-degrees above the horizon. By 6 P.M. it is 22 degrees high and brilliant against the darker skies.
Venus sets at 8:25 P.M. It continues to slowly grow in apparent size as it catches up with Earth and draws closer. A telescope would not only show a slightly larger disk than a week ago, it would also show less of
the sunlit face of Venus. It still appears slightly more than half illuminated as seen from Earth.
Saturn, at magnitude +1.1, is toward the south southwest at 6:00 P.M., 34-degrees above the horizon, and 17-degrees to the upper left of Venus. The planet’s lovely rings, now with their north face tipped just over 5 degrees towards us, are visible in even a modest spotting scope magnifying about 30 times, although easier at 50 to 60-power. The planet’s largest and brightest moon, Titan, is also easy to spot. In a
spotting scope Titan will look like a star just to the upper right of Saturn at 6 P.M. on Monday. At the same time Tuesday, Titan will be well to the lower right. Astronomical telescopes may reverse or invert the view.
Jupiter, at magnitude -2.7, continues to dominate the eastern sky in the early evening. By 8:00 P.M. the gas giant is 57-degrees above the east southeastern horizon. On Monday at 8 P.M. any modest telescope will show three of the planets four Galilean moons, with Io and Ganymede to the west and Callisto well to the east. Europa will be passing in front of Jupiter, and will be hard to spot.
Look for bright Europa in front of the planet, toward the south and about one-quarter of the planet’s diameter in from the western limb. If you can not see the moon, look for its shadow well to the east. The
black shadow of a moon on Jupiter’s cloud-tops is easier to see than the bright moon itself against the bright planet. Europa itself, however, should be easier to spot as it approaches the western limb. Europa will move out from in front of the planet, to the west, at 8:40 P.M., and should be easier to spot shortly before then in front of the darker western limb.
On Tuesday night at 8:00 P.M. a telescope will show Europa and Ganymede to the west of Jupiter and Io and Callisto to the east. (They are mentioned in order of their distance from the planet, the closest being
named first.)
Our Earth, on its faster, inner orbit, continues to catch up with Mars. As Mars grows closer, its apparent size increases and more detail appears through our telescopes. Mars now shines at magnitude -1.2 and
appears 14.2 arcsecond across. We are just over two weeks from opposition, so it will not grow much brighter or much larger. At opposition, on January 15, it will reach magnitude -1.4 and appear 14.6
arcseconds in diameter. At closer, or “favorable” oppositions, it can reach 25 arcseconds. It will next exceed 20 arcseconds around the opposition of July 5, 2033, when it will reach a maximum of 22.1 arcseconds.
Even without a telescope, bright, reddish Mars is a lovely sight. It will be due south and highest, 71-degrees above the horizon, at 1:42 A.M. If you are not a night-owl, catch it 30-degrees above the eastern
horizon at 9:00 P.M.
Happy New Year! May 2025 bring you many clear nights and lovely celestial sights.