Billions and billions of black holes
![[John Kormendy, U of Texas at Austin] A supermassive black hole lurks in the NGC 3115 galaxy](black-hole-ngc3115.jpg) Q: How many black holes do we REALLY know about? -amtrak
A: So far, we have found a supermassive black hole in every bulge galaxy. Bulge galaxies abound: our
own Milky Way, for one. We've discovered 37 supermassive black holes as of March 2001. That number
(33 back in June 2000) is increasing rapidly as we continue to search.
[John Kormendy, U of Texas at Austin] A supermassive black hole lurks in the NGC 3115 galaxy
These black holes have masses of a million to a few billion times the mass of the Sun. The massive black-hole candidate we are most certain about lies at the heart of our own galaxy: a black hole as massive as
about three million Suns dwelling about 25,000 light years from Earth.
On a smaller scale, we know of at least 10 binary stars whose unseen companion is almost certainly a black hole. Each of these black
holes, or invisible stars, is the corpse after the last convulsive collapse of a star that went supernova. Before the supernova explosion, the
stars were about 10 to 20 times the mass of the Sun.
"There are probably millions of stellar-mass black holes-mostly not in binaries and [therefore] not so easily detected-floating around the
disk of the Milky Way galaxy," says John Kormendy, astrophysicist at the University of Texas at Austin.
(Answered by April Holladay, science correspondent, May 15, 2002)
Further Surfing:
U of Texas at Austin: Monsters in galactic nuclei
USATODAY.com: Black hole found at center of Milky Way
Scientific American: The Milky Way's black hole
NASA: Black holes
Space Telescope Science Institute: Black holes
Space.com: First direct evidence of black hole
NASA: Hubble images of black hole holes
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