Celestia Forums

Is the Andromeda Galaxy going to collide with the Milky Way?

I've heard from numerous sources that the Andromeda Galaxy is going to collide with the Milky Way someday.

I understand how its radial velocity relative to the Milky Way is determined through its blueshift, but how do we know its tangental velocity? Without knowing that, how can we conclude that a collision is inevitable, rather than a hyperbolic pass or even a closed orbit of the two galaxies around each other, but without actually colliding.

When I read that "scientists have performed simulations" showing that they will collide, it seems that the simulations only show what would happen if they did collide, rather than predicting the collision itself?

Any thoughts?

I think it is pretty certain that they are going to collide one day. If they did get into a closed orbit they would probably end up spiraling into each other anyway.

Michael Kilderry

Michael Kilderry wrote:I think it is pretty certain that they are going to collide one day. If they did get into a closed orbit they would probably end up spiraling into each other anyway.

Without knowing in what direction the Andromeda Galaxy is moving, it's impossible to tell how close it will get. All we can tell from it having a velocity component towards us, is that it will get closer, just as a comet on its way towards the Sun. Will the galaxies get close enough to spiral into each other? Whether the orbit is closed or not hardly matters a lot; I wonder if the universe will last long enough to allow even for a full orbital pass?

When or if that happens, the human race will have either conquered the entire galaxy and beyond, or gone extinct. So does it really matter what happens in several billion years? Well I should be one to talk, since I am interested in this stuff too, so yeah. I'd say it will collide, and when that happens... Well we wont have to worry about it, since we will all be dead and all the people living in that time, if any will also die, or be flung out of the galaxy and die soon after. Jeez i have such a positive outlook dont I? Forgive me.

lets say our sun was still alive by the time they collided and the earth was also still well and good. The chances of the collission killing life on earth would actually be very small, since the spacing between each star is relatively very distant. The galaxies would merge without a lot of collisions between all the stars. sure some might get flung out but still if our sun was around then and we were also we would have a very good chance at survival.

Could the resulting collision create some sort of mega-super black hole from the combined masses of the two galaxies?
We'd better be somewhere far away if that happens...

I don't think the collision of the black holes would bother us directly. The probability of objects colliding directly would be small, but the probability of stellar systems interacting with each other gravitationally would be consistent. So what we should be worried about is what happens if some supercluster intersects with our own, and some massive star passes through the vicinity of our solar system. Then we'd be in trouble.

Matter of fact, that could even happen without the two galaxies colliding.

Scytale wrote:I don't think the collision of the black holes would bother us directly. The probability of objects colliding directly would be small, but the probability of stellar systems interacting with each other gravitationally would be consistent. So what we should be worried about is what happens if some supercluster intersects with our own, and some massive star passes through the vicinity of our solar system. Then we'd be in trouble.

Matter of fact, that could even happen without the two galaxies colliding.

Would that be the theory of the Nemesis Star?
http://imagine.gsfc.nasa.gov/docs/ask_a ... 130b1.html

Darkshot wrote:...or be flung out of the galaxy and die soon after. Jeez i have such a positive outlook dont I? Forgive me.

If you are talking about an Earthlike planet with it's parent star getting flung out of the galaxy, if they still stay intact together with no disasters on the way then both planet, it's life and star should survive, I don't think it matters if an earthly planet is outside of a galaxy, I think it still would be ok, there may actually be an advantage, less chance of collision with other objects.

Michael Kilderry

This is only a theory. But it is possible for galaxies collide. This what astronomers call a galaxy evolvtion.

the two galaxies' gravity will interfere with each other. then when they collide, Another billion years go by reforming into a elliptical galaxy.
It is possible for the Milky way to colide with Andromeda. Our galaxy will evolve from a sprial to elliptical.

Michael Kilderry said:

If you are talking about an Earthlike planet with it's parent star getting flung out of the galaxy, if they still stay intact together with no disasters on the way then both planet, it's life and star should survive, I don't think it matters if an earthly planet is outside of a galaxy, I think it still would be ok, there may actually be an advantage, less chance of collision with other objects.

The space inbetween the stars is large enough for other stars to fly through. By still possible for stars to collide and who knows what will when they (maybe a supernova). But this would help, if there is life there or we be even alive, that we be closer in contact. we can share our knowledge.

This will tell more:
http://www.galex.caltech.edu/

Stars frequently collide in the centers of globular clusters. Rather than going supernova, they merge to form a single star with the characteristics of a star much younger than either of the "parents.". They're what are called "blue stragglers".

See http://antwrp.gsfc.nasa.gov/apod/ap030808.html