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Q&A: Galaxies, Galaxy Clusters, AGN, and Quasars

Q:
Quasar 3C273
3C294
I read an article about the discovery of merging galaxies. In this article is said that this is happening 10 billion light years away. Does this mean that the events you saw actually happened 10 billion years ago? So at this point shouldn't the galaxies already be merged and maybe transformed into a quasar?

A:
Perhaps you've seen images from the Chandra website of such distant objects. For example, the cluster of galaxies called 3C294 is about 10 billion light years away:

http://chandra.harvard.edu/press/01_releases/press_021501.html

You are correct in your assumption. If an object is 10 billion light years away, and we receive light from it, whatever event caused the light to be emitted happened 10 billion years ago. So indeed, the galaxy merger we view today from Earth has already merged and evolved for 10 billion more years, and probably bears little resemblance to the current image. More information

As to it turning into a quasar, that is actually an open question. It may be that if each galaxy contains a supermassive black hole in the center, then the merging of these black holes could power a quasar (http://chandra.harvard.edu/xray_sources/quasars.html), or more likely a gamma ray burst (http://chandra.harvard.edu/xray_sources/grb.html).

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