The Andromeda Galaxy is autumn's greatest showpiece! It's the largest galaxy of our local group of 30, and the single most distant object visible to the naked eye. The New Moon was on the 6th, so this is a great time to look at the sky. Jupiter and Saturn are still highly visible in the South. Venus is visible low in the SW. So, if you see something bright there, it’s definitely Venus.
Andromeda is 2.5 million light years from us, but the fact that it's visible unaided tells you how big it really is. The Milky Way is 100,000 light years across, and Andromeda is 150,000. So, it's a larger twin of our galaxy. In 2006, the Spitzer Space Telescope revealed that it has one trillion stars, more than twice what the Milky Way has.
This great spiral offers it all: a bright nucleus, dust zones, star clouds, globular clusters and eight satellite galaxies (four of which are visible to us). Its name comes from the Andromeda constellation in which it appears. That was named after the mythological princess, Andromeda.
Andromeda Galaxy is visible on any clear moonless night from late summer to early spring. To find it, look for the "Great Square of Pegasus" about halfway up in the eastern sky. The square looks like a large baseball diamond with a bright star at each corner. Envision the farthest star to the left as third base. The two horizontal streamers flowing to the left of this star are part of the Andromeda constellation. There are three bright stars in each streamer. Find the middle star of each streamer and look slightly above them. The fuzzy patch of light you see is the Andromeda Galaxy! The upper "V" of Cassiopia's "W" also points down to it.
This elongated smear of gray-green light stretches the diameter of two full moons. Only the bright central region is visible to the naked eye. With a telescope, it's six times the width of the full moon, because you also see the spiral arms. Binoculars would show you something in between and make the oval shape more obvious.
If you give your eyes at least 30 minutes to adjust to the dark they will become more sensitive to faint light, and it will be easier to find. Our low humidity also helps. Remember, what you're seeing is how it looked 2.5 million years ago.
The Andromeda Galaxy is racing towards us. The Hubble Telescope showed that in 3-4 billion years it will collide with the Milky Way. The collision will take another 100 million years to complete. The stars are small and far apart, so they won't collide, but what will happen is that the galaxies will merge to form a much larger galaxy. The huge gas clouds will collide and form many new stars. Currently, it takes our Sun 200 million years to complete one orbit around the Milky Way. Imagine how long it will take a star/sun to complete an orbit around this new giant galaxy!