Autumn Night Sky (Northern Hemisphere)

The sky has made another quarter turn in the three months since August as the Earth moves around the Sun.  The Summer Triangle has worked its way westward during the northern autumn.  The rich band of the Milky Way in the constellation Sagittarius disappears into the southwest.  The Big Dipper has turned low in the northeast.  If you have an unobstructed view of the southern horizon, you’ll see the star Fomalhaut (“FOAM-a-lot”) in the constellation Piscis Austrinus, the Southern Fishes.  Because it’s the only bright star in this part of the sky in the northern hemisphere, Fomalhaut is sometimes called the “Lonely Star of Autumn”.

The sky at 9 p.m. on November 15 from 40 degrees N latitude. Click to open in a new window.

The sky at 9 p.m. on November 15 from 40 degrees N latitude. Click to open in a new window.

Rising in the northeast sky, look for the large constellation Perseus and above it the W-shaped constellation Cassiopeia.  This constellation reveals many fine star clusters to an observer with binoculars or a telescope.  Below Perseus, low in the northeast, the brilliant star Capella, which you saw setting in the northwest in the spring, rises again and gets a little higher each night as the autumn wears on. Perhaps the most conspicuous constellation of a northern autumn is Pegasus, the winged horse of Greek legend.  The body of Pegasus comprises the “Great Square”, which lies just southeast of the zenith in mid-November and spans as much sky as your closed fist.  Attached to Pegasus is the constellation Andromeda, which harbors the nearest major galaxy to our own.  The Andromeda Galaxy can be seen easily with the unaided eye in dark sky as a faint, misty, oval patch near the star Mirach in Andromeda.  But don’t underestimate this dim fuzzy patch… it’s actually a galaxy like our own Milky Way, though somewhat larger, with some 200 billion stars.  The light from the Andromeda Galaxy has been traveling through space for 2 million years before it enters your eye.

The “Great Square” of Pegasus lies overhead on northern autumn evenings.  The position of the Andromeda Galaxy is shown in this map

The “Great Square” of Pegasus lies overhead on northern autumn evenings. The position of the Andromeda Galaxy is shown in this map

In November later in the evening look to the east for the rising Pleiades star cluster, which lies within the small V-shaped constellation Taurus, the Bull.  The appearance of Taurus with its bright orange star Aldebaran marks the coming of winter in the northern hemisphere.  East of Taurus, in late November and December look for the grand constellation Orion, the Hunter, rising above the eastern horizon.  The tidy line of three bright stars marks the “belt” of the ancient constellation.