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Big or small, black holes play same melody

Big or small, black holes play same melody

By Richard Stenger

(CNN) -- Massive black holes that dwell in distant galactic centers and diminutive counterparts that reside in nearby star systems have one startling likeness: they play the same energetic song, albeit at different tempos.

British astronomers came to that conclusion after tuning into the X-ray emissions of numerous black holes. They compared the slow variations in emissions from the larger ones with the much more rapid radiation outputs from the smaller siblings.

The former can be as much as a billion times heavier than the sun, feeding on an unstable diet of galactic gas. As matter approaches a central black hole, it compresses and releases fluctuating bursts of energy, including X-rays. Radiation emission variations can last hours or years.

In contrast, much smaller black holes feed off companion star material. Their energy release variations are measured in milliseconds or seconds.

But slow down the variation patterns of the little guys, for example, by a factor of 1 million, and they have an uncanny resemblance to those of the big boys, according to University of Southampton researchers.

"If you were to transcribe the X-ray output of these black holes as a series of musical notes, so greater X-ray output means a higher pitch, it would not sound quite like any particular sort of music, because the variations in X-ray output are essentially random," said astronomer Phil Uttley.

"But the 'tune' will still have a musical quality about it. This is because the general pattern of note changes is the same as you hear in all kinds of music," he said "You could say that these black holes are the ultimate improv artists!"

Uttley and colleagues used NASA's Rossi X-ray Timing Explorer satellite to monitor central galaxy black holes for six years.

That black holes emit variations of the same theme could serve as a valuable tool for astronomy.

"The tape speed setting is the only major difference, and it's governed by the black hole's mass. Bigger black holes show slower variations, so we can use the X-ray variability to measure the mass of the (larger, more distant) black holes," Uttley said.




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