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I know that the Milky Way will collide with Andromeda in the distant future but based on what we know so far there is a supermassive black hole in the center of each galaxy and thus the Milky Way will get sucked into it as well. But before that will it turn into a quasar or something like that?

I was surprised that Wikipedia is so sparse on information in this topic. So how can I visualize its lifecycle?

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Nice question. That the Milky Way galaxy has a super massive black hole at its center doesn't mean that it "will get sucked into it". When it does collide with the Andromeda galaxy, some of its mass will get thrown onto the central black hole(s) (after they coalesce of course- which can take a long time). Whether or not it goes through a quasar phase I am not qualified to speculate. – astromax Nov 21 '13 at 23:52

If we look at Newtonian physics, and how galaxies will interact, a central black hole should just be considered as a massive, dense object.

The Milky Way does not fall into its own central black hole, it orbits it - as physics tells us it should.

When we get closer to Andromeda, the gravitational influence of Andromeda will act more strongly on us, and when we get really close, individual masses within each galaxy will have dramatic effects on each other, but as with any such system, the two black holes will not suck everything in.

If the two galaxies end up coalescing - which is not a given - the orbits of the stars and the black holes will be very complex. For billions of years the 2 black holes will orbit each other, getting closer as they shed energy, but during that time the stars around them will suffer many effects, including:

  • some will be expelled
  • some will hit the black holes
  • some will go nova
  • and so on

The best way to understand what will happen is to avoid thinking too deeply about black holes being weird, and treat them as dense masses. For most purposes this will help you model galactic collisions.

Have a look at this NASA simulation of the collision between the Milky Way and Andromeda:

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An interesting follow-up question I have is whether or not more energy will be 'shed' through gravitational radiation, or through kinematic interactions with surrounding material. – astromax Nov 22 '13 at 16:44
Now that is a question I have no clue about... – Rory Alsop Nov 22 '13 at 19:22

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