ASTRONOMERS have spotted several 鈥渕iddleweight鈥� black holes that they believe
formed when others coalesced.
Black holes usually come in two varieties鈥攕upermassive ones created
when huge gas clouds collapse, and much smaller black holes born in supernovae.
But at a meeting of the American Astrophysical Society in Charleston last week,
astronomers from NASA and Carnegie Mellon University in Pittsburgh announced the
discovery of medium-sized black holes.
These middleweights have a mass equivalent to several hundred Suns, and the
researchers rule out supernovae or collapsing gas clouds as their source. 鈥淭he
most viable theory is that a lot of stellar-size masses merge to create an
intermediate mass range black hole,鈥� says Edward Colbert of NASA鈥檚 Goddard Space
Flight Center near Washington DC.
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