The Autumn Night Sky

As we move into autumn, the time changes, and it starts to get dark earlier. It is a great time to go stargazing. Here are a few notes taken from two earlier FAS Astronomers Blogs.

The Night Sky

During the Fall, find the Great Square of Pegasus to the south. Add a few more stars to find Pegasus itself, the upside-down flying horse, high in the sky. Off to the east of Pegasus is the constellation of Andromeda. If you wait to a little later in the evening, the constellation Perseus will be visible even more toward the east. It looks something like an upside down Y or maybe the wishbone from your Thanksgiving turkey.

The ecliptic (path of the planets) runs well below Pegasus and Andromeda. In 2023, Saturn appears in Aquarius below the neck and head of Pegasus and Jupiter in Cetus below Andromeda.

Turn around and find the queen Cassiopeia to the north looking like a big W or M. Nearby is the faint King Cepheus resembling a child’s drawing of a house. Low in the horizon is the Big Dipper. Follow the two stars at the end of the bowl to find Polaris (the North Star) at the end of the tail of the Little Dipper. Notice that the Little Dipper is always found curved in toward the Big Dipper.

See our webpage about The Night Sky for a few suggested smart phone and tablet apps and links to various star maps including Stellarium Web. The Astronomical League has monthly sky charts (see below). You might also visit the new Kaleideum Digital Dome Planetarium for their sky tours (general museum admission rates apply).

The Deep Sky

To the right and just above the nose of Pegasus (Enif) is the globular cluster [M15]. Draw a line from the intersection of the neck and head of Pegasus (Baham/Theta Pegasi) to Enif and extend it out just under ½ the distance to the cluster.

The faint Andromeda Galaxy (M31) is found in Andromeda. It will appear as a fuzzy patch of light, but through a telescope from a dark sky location you might see the brighter central portion of the galaxy. To find it:

  1. Start with the star in the upper left corner of the Great Square of Pegasus – as it appears when looking south (Alpheratz).
  2. Hop one-two left across the bottom row of the Andromeda constellation through Delta Andromedae to the star Mirach.
  3. Then hop up one-two through Mu Andromedae to find the galaxy.

Below Mirach, around the same distance as to Andromeda, but in the opposite direction is the Triangulum Galaxy [M33]. It is technically in the constellation Triangulum – hence its name. Although a bright galaxy, it is somewhat diffuse, so it might be difficult to see.

For more of a challenge, try to locate the globular cluster [M2] in Aquarius below the head of Pegasus .

  • Draw a line from the lower right corner of the Pegasus great square (Markab/Alpha Pegasi) through the intersection of the neck and head of Pegasus (Baham/Theta Pegasi). Extend it around ¾ of the distance to the cluster.
  • You can also use the top of the constellation Aquarius, which has four stars that make up a “squiggly” shape. Draw a line from Eta Aquarii (the left star) through Sadalmelik/Alpha Aquarii (the right star) and extend it roughly the same distance to the cluster.

The Perseus Double Cluster [C14, NGC 869 and NGC 884] is a Caldwell object worth looking for between Perseus and Cassiopeia.

  • Draw a line from the left base of the triangle at the top of Perseus (Al Fakhbir/Gamma Persei) through the two stars marking the left middle of Cassiopeia’s W or right middle of Cassiopeia’s M (Ruchbah and Navi). The Double Cluster is halfway between Al Fakhbir and Ruchbah.
  • Or draw a line from Navi and Ruchbah through the intersection of the Perseus upside-down Y and brightest star in Perseus (Mirfak). The Double Cluster is around 1/3 of the way from Ruchbah to Mirfak.

Two open clusters are found around Perseus.

  • The Perseus Open Cluster [M34] is located just a bit toward Perseus from the middle of the line between the lower right end of the Perseus upside down Y (Algol) and the end of the lower row of Andromeda (Almach).
  • The Alpha Persei Cluster [Mel 20] is a wide cluster surrounding the star Mirfak.

One of the more interesting open clusters, and another Caldwell object, is the ET/Owl Cluster [C13, NGC 457] found near Cassiopeia. You can see two bright stars for its eyes, two stars for its feet, a row of stars representing its body, and several stars off in either direction for its arms. Many think it looks like an extra-terrestrial (ET) or an owl.

  • It can be found by drawing a line from the left of Cassiopeia’s W or right of Cassiopeia’s M (Segin) to Ruchbah and extending it half that distance. The cluster is just off the line toward Andromeda and Perseus.
  • You can also draw a line from the center star of the W or M (Navi) that intersects with the above line to create a right angle near the cluster.

A Few References

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