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Sunday January 23
Mercury reaches inferior conjunction at 5 a.m. EST. It is now hidden from view by the bright glare of the Sun, but will just begin to appear at dawn as a morning object by the end of the month.
Instead, let’s focus tonight on a fascinating and easy-to-see object: the Pleaides (M45). This large open cluster stretches 110′ across the sky and is already 66° high an hour after sunset. Look south to find this young star cluster about 14° northwest of Aldebaran in Taurus the Bull. Many people think of the Pleiades as looking like a spoon or ladle, and some even confuse it with Ursa Minor (which is much larger, weaker, and located to the north). At least six bright stars are visible to the naked eye, including 5th magnitude Pleione, a known variable. Pleione is a rapidly rotating star whose movement causes changes in its brightness and even in the type of spectrum that astronomers observe. By carefully comparing Pleione’s brightness to that of its neighboring stars over the course of a few observations, you too might be able to tell that it is changing over time!
The American Association of Variable Star Observers has more information about this star and how to observe it as part of its Monthly Featured Variables webpage.
Sunrise: 7:16
Sunset: 5:09 p.m.
Moonrise: 11:07 p.m.
Moon setting: 10:29
Moon phase: Waning gibbous (69%)
monday january 24
Saturn and Jupiter are fast sinking in the evening sky, but the planet Neptune is a slightly less harried affair. The distant planet is still 30° high an hour after sunset, hovering above bright Jupiter and just on the border between Capricorn and Pisces.
First, while it’s still in place, find Jupiter – it’s easy, because the giant planet is a bright magnitude of -2.1. Enjoy a telescopic view of its alternating light and dark belts while you can, as the planet will continue to sink at sunset each day for the rest of the month, blurring its details.
Once it gets dark enough, two 4th magnitude stars will appear to the upper left of Jupiter (northeast): Hydor at 6.2° northeast of Jupiter and Phi (ϕ) Aquarii at 5.5° northeast of Hydor. (Hydor is brighter than Phi.) Another 3.7° northeast of Phi is Neptune, whose magnitude 7.8 glow you’ll notice with binoculars or any small scope. You will notice that it is close (18′) to a magnitude 6 field star – Neptune is the faintest and “flattest” star and may appear gray or blue to your eyes. Its disk currently only spans 2 inches – but that’s because the massive planet is around 2.9 billion miles (4.7 billion kilometers) from Earth.
Sunrise: 7:15 a.m.
Sunset: 5:10 p.m.
Moonrise: —
Moon setting: 10:54
Moon phase: Waning gibbous (59%)
tuesday january 25
The last quarter moon occurs at 8:41 a.m. EST, rising just after midnight on the 24th and holding its highest at dawn. But you don’t have to be an early riser to enjoy this phase, which is visible in bright daytime skies until just before noon.
It is true that early morning sightings before dawn will give you breathtaking views. Now is the time to enjoy the long line of craters walking through the middle of our Moon, as well as the long curve of the Apennines, which form the southeastern edge of Mare Imbrium (the Sea of Rains). Imbrium also shows two large, prominent craters in the waning sunlight: Plato at its top and Archimedes toward its bottom.
Easily visible is the bright, radiant crater Copernicus, which lies southwest of Imbrium. And walking down, just west of the daylight-separating terminator, are large craters that include (among many others) Ptolemaeus, Alphonsus, and Arzachel.
Sunrise: 7:14 a.m.
Sunset: 5:11 p.m.
Moonrise: 00:15
Moon setting: 11:21 a.m.
Moon phase: Ascending descending (48%)
