Space Walk: The Andromeda Galaxy

The Andromeda Galaxy, M31, is one of the largest and most prominent galaxies in the night sky. In fact, it is so large and bright that it is one of the few objects that exists outside of our own galaxy that can be seen with the unaided eye from a dark location. It's so large that it won't even fit in the lowest power field of view in many telescopes. It's a good binocular object, but can show interesting details in the telescope. It is the closest major galaxy to the Milky Way, and is predicted to collide with us, but not for a few billion years, so no need to worry yet.

Link to the mp3 audio file. Download the file to the device you will be using to listen to it in the field.

Andromeda Galaxy Space Walk Among the Stars - audio

Images of M31 taken by amateur astronomers.

Charts to accompany the Space Walk. Review these prior to observing with your telescope.

Chart 1: Finding the general area in the sky. 

Find the Big Dipper and use the "pointer stars" at the end of the "bowl" to find Polaris, the North Star. 

Then find the "W" of Cassiopeia. The point of the "W" on the right has a star off it that will point to Alpheratz. 

Then backtrack along the two chains of stars that make up the constellation Andromeda. Take the second pair of stars and find the third star up, then look offset just a little for a dim little oval cloud.

 Binoculars will help spot it.

Chart 2: Finder chart for the various objects cited in the MP3 guide. The red "+" identifies the core of M31. Stars used to find the various objects are circled in orange. The green lines denote the most easily visible sections of M31's dark dust lanes. You'll need about an 8 to 10 inch telescope and a reasonably dark sky to see them well. The star cloud NGC 206, as well as double stars Struve 44 (STF 44), Struve 64 (STF 64), and Struve 79 (STF 79) are also labeled. 

The red letters at bottom refer to the Bonus Challenge (see below). Notice the orientation has East up and north to the right. All of the following images and charts are in the same orientation, though they vary in scale. 

Image showing some of the features from the Space Walk labeled.

The three stars at top are used to find STF 79 and should be visible in a finderscope. 

The stars identified within the galaxy itself are used to see how far you can trace the glow of the galaxy on the northeastern side in your telescope. Once you have oriented yourself in the telescope you realize that you're only seeing the inner section of the galaxy- the section that looks yellower in the image. The bluer outer arms in images extend much farther out. Note that East is up in this image, which matches the chart above.

Bonus Challenge: Finder image for globular cluster G1 (Mayall II), the brightest globular cluster in the Andromeda Galaxy. Globular clusters exist in a halo around large galaxies. G1 is one of more than 450 globular clusters known to exist in M31. This cluster is 13.7 magnitude, making it visible in a dark sky with moderate to large backyard telescopes, though experienced observers with smaller scopes may be able to pick it out under excellent conditions. 

The yellow letters refer to the red-lettered stars in Chart 2 above. The first image is one degree wide. The yellow rectangle shows the area covered by the detail image that follows, which is 15 arcminutes wide and equates roughly to a telescope's high power field of view. 

The "tiny" galaxy to the lower left of star "A" is UGC 330, at 14.7 magnitude, about 290 million light years away, which is why it appears so small and dim. For reference, star "B" is 8.5 magnitude. Note how far away from M31 the cluster is in the sky, yet it's part of that galaxy (130,000 light years from the core). East is up, north to the right in both images to match the other charts and images.

Close up view of the yellow box above, with globular cluster G1 labeled:

Hubble Space Telescope image of G1 (Mayall II). The cluster is approximately 1,000 light years in diameter. The two stars are the two forming the tiny triangle with G1 in the previous image.