This month ……. The Andromeda Galaxy (M31). On a collision course with the Milky Way it will be visiting us “shortly”
The Andromeda Galaxy is one of the closest galaxies to our own Milky Way and is travelling in our direction at approximately 100 to 140 kilometres per second. In about 4.5 billion years the Andromeda Galaxy and the Milky Way are expected to collide.
The photograph above is by Adam Evans - M31, the Andromeda Galaxy (now with h-alpha)Uploaded by NotFromUtrecht, CC BY 2.0, https://commons.wikimedia.org/w/index.php?curid=12654493
At a distance of 2.5 million light years the Andromeda Galaxy is the most distant object you can see with the naked eye and with an apparent magnitude of 3.4 is among the brightest of the Messier objects
The Andromeda Galaxy is over two and a half times the size of the Milky Way and contains around a trillion stars compared to between 100 and 400 billion stars for our own Milky Way galaxy.
When you look at the Andromeda galaxy the light you are seeing took 2.5 million years to reach you. You are seeing the galaxy as it was 2.5 million years ago.
The galaxy is named after Andromeda, a princess in Greek mythology, the daughter of King Cepheus and Queen Cassiopeia. The painting below is by renaissance artist, Titian, and it is in the Wallace Collection in London. The painting portrays Perseus killing the dragon after which he will save Andromeda, who has been left as a sacrifice by her parents.