Mirach is the guide star to 3 galaxies

Here is the Great Square of Pegasus, connected to the Andromeda constellation through the star Alpheratz. People often find the Andromeda Galaxy (M31), the large spiral galaxy next to our Milky Way, jumping stars from Alpheratz, to Mirach and Mu Andromedae, into the galaxy.

Mirach, also known as Beta Andromedae, is a moderately bright star in the constellationAndromeda. It is a larger and more massive star than our sun, with about three to four times the mass of the sun and 100 times the diameter of the sun, shining with about 2000 times the total brightness of our sun. It is what is known as a red giant star, in the final stages of its evolution, a star whose outer layers have expanded. But Mirach is quite far away at 197 light-years, and so it shines in our sky at only 2nd magnitude, a respectable brightness but not as bright as many other stars.

However, Mirach is an important star for stargazers, who often use this star to guide them in locating three galaxies: the Andromeda Galaxy (M31), the Triangulum Galaxy (M33), and a galaxy known as Mirach’s. Ghost (NGC 404).

The Andromeda Galaxy is possible to spot with the naked eye or with binoculars in a dark, moonless night sky. The other two galaxies are much fainter. You will likely need a telescope to see them.

Use Mirach to find the Andromeda Galaxy (M31). Draw an imaginary line from Mirach to the star Mu (µ) Andromedae. Then continue to extend that line about the same distance between those two stars to get to the Andromeda Galaxy.

Beneath dark, moonless skies, to the naked eye, the Andromeda Galaxy appears as a speck in the sky. Even if the moon is outside or under skies with moderate light pollution (like suburbs), you can see it through binoculars. At approximately 2.5 million light-years away, the Andromeda Galaxy is the closest large spiral galaxy to our Milky Way, and it is as distant as can be seen with the naked eye.

Use Mirach to find the Triangulum galaxy (M33). The Triangulum Galaxy, in the Triangulum constellation, is much fainter than the Andromeda Galaxy. Some people with excellent eyesight have been able to see it, without the aid of telescopes or binoculars, in extraordinarily good viewing conditions. Even so, it can still be a challenge to find M33 with binoculars and small telescopes.