M31 is the deep-sky object that made me want to do astrophography. This light travelled for 2.5 million years before reaching my yard in Victoria, BC in the early September.
The Andromeda is closest galaxy to our Milky Way Galaxy. It is 152,000 light-years in diameter, contains approximately 1 trillion stars and is moving towards us at 110 kilometres per second. Our galaxies will collide in about 4.5 billion years, eventually forming a single giant elliptical galaxy.
The chance of any stars colliding is actually negligibly small, because despite their great numbers, the distances between the stars are tremendous. The two galaxies will simply pass through each other, as they commonly do. In fact, the M31 itself merged with another galaxy 3 billion years ago.
However, both the Milky Way and the Andromeda galaxies have supermassive black holes in their centres, and when they eventually merge, they would form a quasar and release as much energy as about 100 million supernova explosions. According to the current models, there is a 12% chance that our Sun would get ejected from the new galaxy during the collision, in which case the star itself, as well as its planets would be undisturbed. However, if the Sun comes close to the new black hole, it would be torn apart by its gravity.
This will be of little consequence to the life on our planet, though, because much earlier than that, about 1 billion years from now, the Sun’s luminosity will increase by approximately 40%, and there will be no way for liquid water and terrestrial life to exist on Earth.
Time to introduce planetary engineering into our curriculum?