Seeing Giant Galaxies
We’ve begun the season to look for the farthest object a human eyeball can see without help – the Andromeda Galaxy, or Messier 31. This large spiral galaxy is a sister to our own Milky Way galaxy. It sits 2.5 million light-years away from our sun, meaning that its stars’ light has been journeying for that length of time.
Under dark skies, using unaided eyes only, you should be able to see a faint fuzzy patch that is elongated left to right. The galaxy spans six full moon diameters across the sky, but only its bright core and the surrounding, inner halo are usually seen visually. The galaxy is quite easy to see with binoculars.
Because their fields of view are too narrow to see the entire galaxy, small telescopes generally only show its bright core. While looking, see if you can see M31’s two small, fuzzy-looking companions, the small elliptical galaxies designated M32 and M110. M32 is closer to the main galaxy’s core and is situated just to the lower right (or to the celestial south). M110 is above (or northeast of) the main core and is slightly farther away. At 2.49 million light-years, M32 is closer to us than the Andromeda Galaxy; while M110 is 200,000 light-years farther away.
In late September, the Andromeda Galaxy is about halfway up the east-northeastern sky at 10 pm EDT (That is, lower than that before 10 pm, and higher later than 10 pm). To locate it, you can first find the medium-bright star Mirach. It’s the second star east of the eastern corner of the Great Square of Pegasus. Then look for a dimmer star about 4 finger widths above Mirach. The galaxy is higher by that same distance. Alternatively, you can use the highest three stars of the W-shaped constellation Cassiopeia (the Queen). Those three bright stars form an arrow that points directly at M31.
Get more tips and facts on observing celestial objects in the night sky in our Star Walk 2 app!