Black Hole Hums a Note of Distinction

Big black holes sing bass.

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 Tuesday.

“The intensity of the sound is comparable to human speech,” said Andrew Fabian of the Institute of Astronomy in Cambridge, England. But the pitch of the sound is about 57 octaves below middle C.

This is far deeper than humans can hear, and the researchers believe it is the deepest note ever detected.

The sound is emanating from the Perseus Cluster, a giant clump of galaxies some 250 million light-years from Earth.

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 lay there, and the activity around the center bolstered this assumption.

When scientists focused 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. “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, which create the 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.