The title of the this post is a fact. Our own mortality is, truly, inevitable. However, the “We’re” that I am referring to is our theoretical descendants, around 3.75 billion years from now. But many scientists believe that this event will not cause the end of Earth. In full disclosure, its much more likely that the death of our solar system’s sun will cause our planet’s death than what is discussed in this post.
Regardless, a possible cause of our descendants’ deaths is the collision of the Andromeda and Milky Way galaxies. We will start by establishing some facts about Andromeda, as many do not know as much about one of the closest galaxies to our own.
The Andromeda Galaxy.
The Andromeda Galaxy
Andromeda, the Milky Way, and Triangulum are the three largest galaxies in our Local Group of Galaxies. Triangulum is much smaller, but Andromeda and the Milky Way are approximately equal in size (we used to believe that Andromeda was much larger than us, however new technology for measuring galaxy mass has determined that it is much smaller). Andromeda is also the most distant astrological object you can see unaided in the night sky (although you need a great spot away from light pollution to see it).
Because of its similar mass to the Milky Way, the Andromeda and Milky Way galaxies are drawn towards each other through a mutual gravitational pull. This results in the Andromeda Galaxy hurtling towards us at at least 250,000 miles per hour.
I know, this sounds absolutely terrifying. Two galaxies colliding sounds like the end of all life on Earth. But many scientists believe that Earth will survive the collision, based on its position in the Milky Way, and the only major difference will be that our night sky will look entirely different. A video off of Business Insider is very interesting in showing the possible appearances of our sky.
But what will happen to the Milky Way?
Currently, our galaxy and Andromeda are spiral galaxies. This is a less common type of galaxy, and studying Andromeda has actually helped scientists greatly in determining the origin of the category. However, once the two galaxies collide, they will completely rip each other apart, parts of their galaxies shifting from their original positions as the supermassive black holes thought to be at the center of each galaxy meet for the first time. They will then throw each other away, and eventually come back together to form a massive elliptical galaxy (the most common shape of a galaxy in the known universe). (NASA Hyperwall released a great video on what this would look like.)
Ultimately, for our descendants, not much will change. They will probably be more focused on the imminent death of the sun (stay tuned for a post on that), as its predicted time of death is approximately 3.5-4 billion years from now.
However, personally, I am disappointed that I will not be able to see the night sky as it will look after the collision. I’m sure it will be stellar.
Sources:
https://svs.gsfc.nasa.gov/30955
https://www.businessinsider.com/milky-way-andromeda-galaxy-collision-space-nasa-hubble-2016-1
https://www.forbes.com/sites/jillianscudder/2016/11/27/astroquizzical-milky-way-collide-andromeda/#16009db96574
https://space-facts.com/andromeda/