Big black holes sing bass

Black Holes Sing Bass, but Humans Can't Hear Them

Updated 1:23 PM ET September 9, 2003

By Deborah Zabarenko

WASHINGTON (Reuters)
One particularly monstrous black hole has probably been humming B flat
for billions of years, but at a pitch no human could hear, let alone
sing, astronomers said on Tuesday.

"The intensity of the sound is comparable to human speech," said Andrew
Fabian of the Institute of Astronomy at Cambridge, England. But the
pitch of the sound is about 57 octaves below middle C, roughly the
middle of a standard piano keyboard.

This is far, far deeper than humans can hear, the researchers said, and
they believe 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. A light-year is about
6 trillion miles, the distance light travels in a year.

Fabian and his colleagues used NASA's orbiting Chandra X-Ray Observatory
to investigate X-rays coming from the cluster's heart. Researchers
presumed that a supermassive black hole, with perhaps 2.5 billion times
the mass of our sun, lay there, and the activity around the center
bolstered this assumption.

Black holes are powerful matter-sucking drains in space, and astronomers
believe most galaxies, including our own Milky Way, may contain black
holes at their centers. Black holes have not been directly observed,
because their gravitational pull is so strong that nothing, not even
light, can escape it.

SOUND WAVES

So researchers have concentrated on what happens around the edges of
black holes, just before matter is pulled in. When scientists trained
the Chandra observatory on the center of Perseus last year, they saw
concentric ripples in the cosmic gas that fills the space between the
galaxies in the cluster.

"We're dealing with enormous scales here," Fabian said in a telephone
interview. "The size of these ripples is 30,000 light-years."

Fabian said the 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, he said, 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.

To scientists, he said, 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 of the
sound.

Fabian said the notion of singing black holes might well be extrapolated
to other galaxies, but not necessarily to the Milky Way.

Chandra has 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.

I think the Beatles did something like that at the end of "A Day in the
Life."
Marty

On Tue, 9 Sep 2003 17:41:38 -0500 (CDT), (Marty)
wrote:

I think the Beatles did something like that at the end of "A Day in the
Life."
Marty


Correct, it was meant to annoy dogs.

Am I the only one who has noticed that "57 octaves" below Middle C is
about *9 million years*? "too low to hear" is a heroic understatement...