As the Moon wanes this week, it will be seven degrees to the celestial west of Jupiter. As it waxes a couple days later, it will be two degrees to the celestial southeast of Mercury.
Tuesday, January 21 all night — Comet C/2017 T2 (PanSTARRS) passes the Heart and Soul Nebulas
In the northern sky on the nights surrounding Tuesday, January 21, the orbital motion of Comet C/2017 T2 PanSTARRS (red track with annotated dates and times) will carry it past the well-known pair of nebulas in Cassiopeia known as the Heart and Soul nebulas (also designated IC 1805 and IC 1848), setting up a wonderful astro-imaging and observing opportunity while the sky is moonless. The comet, which should be readily visible during January in binoculars as a dim fuzzy patch, possibly with a tail, is predicted to reach peak visibility in late spring 2020.
Wednesday, January 22 before sunrise — Old Moon over Jupiter
Look just above the southeastern horizon before sunrise on Wednesday, January 22 for the very old, slim crescent Moon sitting a generous palm’s width to the upper right (or seven degrees to the celestial west) of Jupiter. That bright planet will rise at about 6:30 a.m. local time. About fifteen hours later, the Moon’s eastward orbital motion will produce an occultation of Jupiter for observers in Madagascar, the Kerguelen Islands, southern and eastern Australia, New Zealand, southern and eastern Melanesia, and southwestern Polynesia.
Friday, January 24 at 21:42 GMT — New Moon
When at its new phase, the Moon is travelling between Earth and the Sun. Since sunlight can only reach the side of the Moon that faces away from Earth, and the Moon is in the same region of the sky as the Sun, our natural satellite becomes completely hidden from view for about a day.
Saturday, January 25 after sunset – Young Moon near Mercury
Very low in the west-southwestern sky immediately after sunset on Saturday, January 25, the very thin crescent of the young Moon will be positioned less than two finger widths to the left (or within two degrees to the celestial southeast) of Mercury. The best time to see the pair will be between 5:30 and 5:45 p.m. local time — but ensure that the Sun has completely set before scanning the sky with binoculars (red circle) or a telescope.
Chris Vaughan is a science writer, geophysicist, astronomer, planetary scientist and an “outreach RASCal.” He writes Astronomy Skylights, and you can follow him on Twitter at @astrogeoguy. He can also bring his Digital Starlab portable inflatable planetarium to your school or other daytime or evening event. Contact him through AstroGeo.ca to tour the universe together.