http://www.nature.com/nsu/030908/030908-14.html
Black hole makes deepest-ever note
An immense black hole 250 million light years away is blowing the lowest B flat ever heard.
It sits at the hub of a giant galaxy called NGC 1275, in the Perseus cluster of galaxies. The satellite-borne Chandra X-ray Observatory has spotted ripples in the gas dispersed throughout the cluster.
These ripples of high- and low-density gas are like sound waves in air. But their frequency is far lower than the deepest sound audible to the human ear. A piano capable of producing the note would have 57 octaves below middle C and would be more than 15 metres long.
The sound waves carry immense amounts of energy away from the black hole, heating up the surrounding gas. Researchers suspected that the gas in clusters such as Perseus must be kept warm, but they did not know how.
The booming black hole also stifles star formation. Without the injection of acoustic energy, the gas would cool, reducing its pressure and allowing it to sink into the cluster's centre. This increase in gas density would trigger its collapse and break-up into blobs that would become new stars.
Chandra detects X-rays emitted by hot gas around NGC 1275. Previously the satellite revealed that there are two vast bubbles in this gas, apparently emanating from the galaxy's massive central black hole.
The black hole is gobbling up gas and dust. This becomes immensely heated, and shoots back out as two hot jets in opposite directions from the vortex-like heart of the galaxy. These jets blow out the two bubbles.
The ripples around the bubbles suggest that their growth excites sound waves in the gas, say discoverers Andy Fabian of the University of Cambridge, UK, and colleagues. The distance between successive peaks in the ripples - the wavelength of the sound waves - is about 36,000 light years.
The researchers calculate that the sound waves' heating effect could balance the steady cooling of the gas. Each bubble would have to be blown continuously for around ten million years before detaching from the galaxy core and moving through the gas.
Black hole makes deepest-ever note
An immense black hole 250 million light years away is blowing the lowest B flat ever heard.
It sits at the hub of a giant galaxy called NGC 1275, in the Perseus cluster of galaxies. The satellite-borne Chandra X-ray Observatory has spotted ripples in the gas dispersed throughout the cluster.
These ripples of high- and low-density gas are like sound waves in air. But their frequency is far lower than the deepest sound audible to the human ear. A piano capable of producing the note would have 57 octaves below middle C and would be more than 15 metres long.
The sound waves carry immense amounts of energy away from the black hole, heating up the surrounding gas. Researchers suspected that the gas in clusters such as Perseus must be kept warm, but they did not know how.
The booming black hole also stifles star formation. Without the injection of acoustic energy, the gas would cool, reducing its pressure and allowing it to sink into the cluster's centre. This increase in gas density would trigger its collapse and break-up into blobs that would become new stars.
Chandra detects X-rays emitted by hot gas around NGC 1275. Previously the satellite revealed that there are two vast bubbles in this gas, apparently emanating from the galaxy's massive central black hole.
The black hole is gobbling up gas and dust. This becomes immensely heated, and shoots back out as two hot jets in opposite directions from the vortex-like heart of the galaxy. These jets blow out the two bubbles.
The ripples around the bubbles suggest that their growth excites sound waves in the gas, say discoverers Andy Fabian of the University of Cambridge, UK, and colleagues. The distance between successive peaks in the ripples - the wavelength of the sound waves - is about 36,000 light years.
The researchers calculate that the sound waves' heating effect could balance the steady cooling of the gas. Each bubble would have to be blown continuously for around ten million years before detaching from the galaxy core and moving through the gas.
They've been found to be especially important in the structure of stars. The idea of a musical universe is incredibly appealing - even if they sound like littlemissattitude squeaking on a clarinet. 
