21 July 2010

When galaxies collide

Two galaxies are squaring off in Corvus and here are the latest pictures. But when two galaxies collide, the stars that compose them usually do not. That's because galaxies are mostly empty space and, however bright, stars only take up only a small amount of that space. During the slow, hundred million year collision, one galaxy can still rip the other apart gravitationally, and dust and gas common to both galaxies does collide. In this clash of the titans, dark dust pillars mark massive molecular clouds are being compressed during the galactic encounter, causing the rapid birth of millions of stars, some of which are gravitationally bound together in massive star clusters.


  1. Awesome photo. Pretty awesome event going on there, too.

  2. Just curious as to how collisions of galaxies would be explained under the theory of the universe expanding I learned in school. Or has the theory been modified, and the universe is no longer expanding?

  3. Mike, I didn't know, so I had to Google your question to find the answer:

    Anyway it's quite natural for galaxies to collide even though the universe is expanding - although I could see why you might get confused about it. What happens is that there is a battle between the forces of gravity between the two galaxies (which is trying to pull them together) and the expansion of the universe (which is trying to pull them apart). With galaxies that start out quite close together, it is almost always gravity that wins, so in the end the galaxies will collide. This will most likely happen to the Milky Way and the Andromeda galaxy (our nearest large neighbour) in a few billion years.

    More at this Cornell University link -


  4. From what I have heard, evidently Scientists have recently discovered that the Milky Way is colliding with another Galaxy right now. I don't know if that is true, but it gives you an idea of what life in one of those is like.


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