A new census
compiled by astronomers contains the location of every local galaxy with a supermassive black hole at its center.
"We
are confident we are seeing every, active supermassive
black hole within 400-million-light-years of Earth," said Jack Tueller of NASA Goddard Space Flight Center in Maryland who led the
census effort.
Called active
galactic nuclei, or AGN, these black holes have masses of up to billions of
Suns compressed into a region about the size of our solar system. The all-sky
census [image],
performed using NASA's Swift satellite over a nine-month period, detected more
than 200 nearby AGN.
Supermassive black holes are thought to lie at the hearts of nearly every massive galaxy, but only a few percent appear
to be active. The black holes of
some galaxies, like our Milky Way,
were likely once active but are now dormant for reasons that are still unclear.
One idea is that they've simply consumed all the material in their immediate
vicinities. Such dormant supermassive black holes
were not counted in the survey.
Among the
key findings from the survey [image]
was the detection of AGN in so-called "starbursts"
galaxies with intense star forming activity. These discoveries will enable
scientists to test a theory called "co-evolution,"
which states that black hole activity and star formation go hand in hand, the
researchers say.
The
findings were presented at a press conference today at the meeting of the
American Astronomical Society's High Energy Astrophysics Division in San Francisco.
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