Scientists: Black hole in Virgo cluster of galaxies hums

NASA scientists have detected a gigantic sonic boom and a "musical" of deep sounds generated by a supermassive black hole in the Virgo cluster of galaxies.

"We can tell that many deep and different sounds have been rumbling through this cluster for most of the lifetime of the universe," said William Forman of the Harvard-Smithsonian Center for Astrophysics Thursday.

The scientists, using NASA's Chandra X-ray Observatory, made the discovery by using data from the longest X-ray observation ever of M87, a giant elliptical galaxy located in the Virgo cluster of galaxies and known to harbor one of the universe's most massive black holes.

The loops and rings in the hot, X-ray emitting gas that surrounds M87 indicate periodic eruptions that occur near the black hole, generating pressure waves in the gas that manifest themselves as sound.

Scientists say that the outbursts occur when material falls toward the black hole. While most of the matter was devoured, some of it was violently ejected in jets.

These outbursts occur every few million years and prevent the gas from cooling and forming new stars, which is why M87 has retained its elliptical shape, they explained.

Chandra's M87 observations also give the strongest evidence to date of a shock wave produced by the black hole, a clear sign of a powerful explosion. The shock wave appears as a nearly circular ring of high-energy X-rays that is 85,000 light-years in diameter and centered on the black hole.

Musically, the sound in M87 appears to be discordant and complex, with some sound waves implying a note around 56 octaves below middle C. The presence of the large cavity and the sonic boom gives evidence for even deeper notes -- 58 or 59 octaves below middle C -- powered by large outbursts.

The new results on M87 were presented during the High-Energy Astrophysics Division meeting last week in San Francisco.

Xinhua/Agencies