Skywatch Line for Friday, January 5, through Sunday, January 7, 2024 written by Sam Salem
This is Dudley Observatory’s Skywatch Line for Friday, January 5, through Sunday, January 7, written by Sam Salem.
On Friday, Sun rises at 7:26am and sets at 4:35pm; Moon rises at 1:18am and sets at 12:04pm.
Venus and Mercury are in the morning sky. Bright Jupiter is visible most of the night. Saturn shines steadily after sunset.
Jupiter, at magnitude –2.6 in the constellation Aries, is the bright white dot dominating the high southeast to south these evenings. It stands at its highest around 8pm. It has shrunk since opposition but still appears 44 or 43 arcseconds wide in a telescope.
Saturday is a busy evening among Jupiter’s moons with four pairs of events, including a double shadow transit. Io disappears into occultation behind Jupiter’s western edge, at 5:47pm. Nine minutes later, Ganymede emerges from in front of the same edge. These two events will only be visible from the Eastern and Atlantic time zones, and the sky there may still be bright with twilight. At 8:27pm, Europa exits Jupiter’s west limb. Nine minutes later Europa’s tiny black shadow, trailing behind, comes onto Jupiter’s opposite limb. At 10:13pm, Io emerges from eclipse by Jupiter’s shadow a small distance off the planet’s east edge. Seven minutes later Ganymede’s shadow crosses onto Jupiter’s opposite edge, thus beginning a 35-minute period of two shadows in transit at once. At 10:55pm, Io’s shadow leaves the western limb. At 11:58pm, Ganymede’s larger shadow does the same. The Great Red Spot crosses Jupiter’s central meridian around 11:05pm.
Mercury shines low in the dawn this week to the lower left of bright Venus. Their separation shrinks to 14° on Saturday. During this time Mercury brightens rapidly by 2½ times, from magnitude +1.0 to 0.0.
Venus, at magnitude –4.0 in the constellation of Libra, shines as the bright “Morning Star” in the southeast before and during dawn. It’s getting a little lower every week. Below or lower right of Venus is sparkly orange Antares.
Saturn, at magnitude +0.9 in the constellation of Aquarius, is getting lower in the southwest during and after dusk. Fomalhaut sits nearly two fists to Saturn’s lower left. Saturn sets around 9pm.
The brightest asteroid in the sky, 4 Vesta, is just past opposition and creeping toward Zeta Tauri, the dimmer horntip of Taurus near the top of Orion’s club. Binoculars will show Vesta easily at magnitude 6.5. But you’ll need a fine-scale finder chart to tell it from all the other faint pinpoints in the area. Vesta will pass 0.2° from Zeta Tau on the Sunday and Monday nights. Then it will cruise about ½° south of the dim Crab Nebula, M1, on January 11th, 12th, and 13th.