15 June 2011

Chicken or the Egg Question Answered?

One of the most fascinating findings in astronomy over the last decade has been the unique relationship between galaxies and the supermassive black holes lurking in their centers.  Rather than being rare, a giant black hole appears to reside in each and every elliptical or spiral galaxy throughout the cosmos.

Illustration of an active, supermassive
black hole in a galaxy's center
But which came first? The giant black hole, drawing in material to help form the galaxy, or did the galaxy form first, generating the environment for a dense collection of matter to collapse into a black hole at its heart?  

Astronomers and theorists from Yale, Rutgers, and the Universities of Hawaii and Michigan have now gathered evidence suggesting that each galaxy and its black hole grow in tandem, starting less than a billion years after the Big Bang.  As reported in the journal Nature, the team revealed this by looking at some 250 distant galaxies earlier spotted by the Hubble Space Telescope and searching with the Chandra X-Ray Observatory for the x-ray signals being emitted from each galaxy's central black hole.  What they find is a distinct connection: the black holes growing and evolving over time along with their host galaxies. "This finding," says team member Kevin Schawinski of Yale University, "tells us there is a symbiotic relationship between black holes and their galaxies that has existed since the dawn of time."  
Image Credit: NASA Goddard Space Flight Center

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