This is the Dudley Observatory Skywatch Line for Monday, and Tuesday, January 27th and 28th, written by Joe Slomka.
The Sun sets at 5:01 PM; night falls at 6:39. Dawn breaks at 5:36 AM and ends with the Sun rising at 7:14.
The Moon and Venus, both in Aquarius, dominate the early evening sky. Monday, Venus blazes with minus 4th magnitude high in the southwest, appears about 15 arc-seconds in size and appears about 75% illuminated. The waxing Moon lies about 6° below Venus, appears about one half degree in size and 9% illuminated. The Moon sets at 7:49 PM on Monday. Tuesday, Venus now appears about 4° north of the Moon, which now appears about 16% lit and sets at 8:49 PM. Venus sets at 8:19 PM.
One hour past Monday’s sunset, Neptune, also in Aquarius, appears less than 1° below Venus, shining with 8th magnitude, 12 magnitudes fainter than Venus, and about 2 arc-seconds in size; Neptune sets at 8:18 PM. Tuesday, Mercury, in Capricornus, may be spotted with difficulty. It lies very low in the southwest, shines with minus 1st magnitude, appears 92% lit, and sets at 5:51 PM; elusive Mercury probably requires an unobstructed southwestern horizon.
Nightfall also reveals Uranus, in Aries, brighter with 6th magnitude, 3 arc-seconds in size and sets at 12:26 AM. Finder charts for Neptune and Uranus can be found in astronomy magazines and websites.
The Dawn sky is becoming crowded. Mars rises in Ophiuchus at 4:01 AM. The Red Planet shines with 1st magnitude and appears about 5 arc-seconds in size. It still close enough to Antares in Scorpius for comparisons between the two red rivals. Jupiter rises about 5:56 in Sagittarius, shining with minus 1st magnitude and appearing a large 32 arc-seconds in size. It should be bright and large enough to be seen by the naked eye about 7 AM. Saturn, also in Sagittarius, rises at 5:56 AM, shining with zero magnitude and appears half Jupiter’s size
Throughout the night, star clusters abound. In early evening, we find the Pleiades above the shoulders of Taurus. The Bull’s face is made of another star cluster, the Hyades. The nearby constellation Auriga harbors three clusters. Finally, Cancer contains the Beehive and M 67.
All these are called “Open Clusters.” They appear to contain, at most, a few hundred stars, which are widely spaced and irregularly shaped. Open clusters are relatively young, less than a billion years old. They reside in the disk of a galaxy and are relatively small, about 50 light-years across.
There is another class of star clusters. These are called “Globular Clusters.” Globular clusters are usually found around galaxy halos and central bulges. Globulars may contain up to a million stars and are quite large, in a sphere about 100 light-years across. These stars are quite old.
If tonight’s weather is clear, binoculars can show many Open Clusters. Just dress warmly and observe the Hyades, Pleiades and the nearby pentagon shaped constellation Auriga.