Yahoo! News Sat, Oct 04, 2003 Science - Reuters Black Holes Sing Bass, But Humans Can't Hear Them
One particularly monstrous black hole has probably been humming B flat for billions of years, but at a pitch no human ould hear, let alone sing... it is the deepest note ever detected in the universe.
The sound is emanating from the Perseus Cluster, a giant clump of galaxies some 250 million light-years from Earth.
... presumed that a supermassive black hole, with perhaps 2.5 billion times the mass of our sun...
Black holes are powerful matter-sucking drains in space, ... gravitational pull is so strong... not even light, can escape it.
SOUND WAVES
... have concentrated on what happens around the edges of black holes, just before matter is pulled in.
... they saw concentric ripples in the cosmic gas that fills the space between the galaxies in the cluster.
... ripples were caused by the rhythmic squeezing and heating of the cosmic gas by the intense gravitational pressure of the jumble of galaxies packed together in the cluster.
As the black hole pulls material in, it also creates jets of material shooting out above and below it, and it is these powerful jets that create the pressure that creates the sound waves.
... pressure ripples equate to sound waves.
By calculating how far apart the ripples were, and how fast sound might travel there, the team of researchers determined the musical note...
... the notion of singing black holes might well be extrapolated to other galaxies, but not necessarily to the Milky Way.
... looked at X-ray emissions from the Milky Way's center, and astronomers believe there is a black hole there, but because it is a young, rambunctious galaxy with lots of activity at its heart, this may interfere with any note our black hole might sing, Fabian said.
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