From: mk_thisisit
Astronomers have observed that the Andromeda Galaxy and the Milky Way Galaxy are on a collision course and will eventually collide [00:00:18] [00:05:09].
Collision Dynamics
While this collision might seem catastrophic, it is not expected to mean the end of our galaxy [00:05:20]. The galaxies will likely pass through each other, then return, stop, and eventually merge to become one larger galaxy [00:05:28]. Andromeda is larger than the Milky Way and will primarily absorb it [00:05:34].
Role of Black Holes
In the center of the Andromeda Galaxy, there is a much larger black hole compared to the Milky Way’s central black hole [00:05:39] [00:05:54]. When the galaxies collide, these black holes will start to fill each other up until they finally absorb each other [00:05:44]. This larger black hole will then begin to absorb the entire galaxy cluster [00:06:00].
Our local cluster contains about four or five galaxies, but much larger clusters exist with millions of galaxies [00:06:06]. Eventually, these too will be swallowed by a supermassive black hole [00:06:14]. It will also start swallowing stars, with most of them going into the supermassive black hole [00:06:22].
The “Boring Era”
This process will lead to a “boring era” where a single, massive black hole exists and endures for an incredibly long period, estimated to be around 10 to the hundredth power of years (1 followed by 100 zeros) [00:06:30]. This is the estimated time it takes for black holes to finally evaporate through the Hawking radiation phenomenon [00:06:44].