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Chandra 'Hears' A Black Hole
Donald Savage Headquarters, Washington (Phone: 202/358-1727) September 9, 2003 Steve Roy Marshall Space Flight Center, Huntsville, Ala. (Phone: 256/544-6535) Megan Watzke Chandra X-ray Observatory Center, CfA, Cambridge, Mass. (Phone: 617/496-7998) RELEASE: 03-284 CHANDRA "HEARS" A BLACK HOLE NASA's Chandra X-ray Observatory detected sound waves, for the first time, from a super-massive black hole. The "note" is the deepest ever detected from an object in the universe. The tremendous amounts of energy carried by these sound waves may solve a longstanding problem in astrophysics. The black hole resides in the Perseus cluster, located 250 million light years from Earth. In 2002, astronomers obtained a deep Chandra observation that shows ripples in the gas filling the cluster. These ripples are evidence for sound waves that have traveled hundreds of thousands of light years away from the cluster's central black hole. "We have observed the prodigious amounts of light and heat created by black holes, now we have detected the sound," said Andrew Fabian of the Institute of Astronomy (IoA) in Cambridge, England, and leader of the study. In musical terms, the pitch of the sound generated by the black hole translates into the note of B flat. But, a human would have no chance of hearing this cosmic performance, because the note is 57 octaves lower than middle-C (by comparison a typical piano contains only about seven octaves). At a frequency over a million, billion times deeper than the limits of human hearing, this is the deepest note ever detected from an object in the universe. "The Perseus sound waves are much more than just an interesting form of black hole acoustics," said Steve Allen, also of the IoA and a co-investigator in the research. "These sound waves may be the key in figuring out how galaxy clusters, the largest structures in the universe, grow," Allen said. For years astronomers have tried to understand why there is so much hot gas in galaxy clusters and so little cool gas. Hot gas glowing with X-rays should cool, and the dense central gas should cool the fastest. The pressure in this cool central gas should then fall, causing gas further out to sink in towards the galaxy, forming trillions of stars along the way. Scant evidence has been found for such a flow of cool gas or star formation. This forced astronomers to invent several different ways to explain why the gas contained in clusters remained hot, and, until now, none of them was satisfactory. Heating caused by a central black hole has long been considered a good way to prevent cluster gas from cooling. Although jets have been observed at radio wavelengths, their effect on cluster gas was unclear since this gas is only detectable in X-rays, and early X-ray observations did not have Chandra's ability to find detailed structure. Previous Chandra observations of the Perseus cluster showed two vast, bubble-shaped cavities in the cluster gas extending away from the central black hole. Jets of material pushing back the cluster gas have formed these X-ray cavities, which are bright sources of radio waves. They have long been suspected of heating the surrounding gas, but the mechanism was unknown. The sound waves, seen spreading out from the cavities in the recent Chandra observation, could provide this heating mechanism. A tremendous amount of energy is needed to generate the cavities, as much as the combined energy from 100 million supernovae. Much of this energy is carried by the sound waves and should dissipate in the cluster gas, keeping the gas warm and possibly preventing a cooling flow. If so, the B-flat pitch of the sound wave, 57 octaves below middle-C, would have remained roughly constant for about 2.5 billion years. Perseus is the brightest cluster of galaxies in X-rays, and therefore was a perfect Chandra target for finding sound waves rippling through the hot cluster gas. Other clusters show X-ray cavities, and future Chandra observations may yet detect sound waves in these objects. For images and additional information on the Internet, visit: http://chandra.nasa.gov http://chandra.harvard.edu -end- |
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Chandra 'Hears' A Black Hole
On a sunny day (9 Sep 2003 18:59:12 GMT) it happened
(Ron Baalke) wrote in : If so, the B-flat pitch of the sound wave, 57 octaves below middle-C, would have remained roughly constant for about 2.5 billion years. Is it out of order to just write a frequency in Hz? Like nn Hz? (maybe float). At least I would have some idea. Or how about 'radio waves that are 57 octaves below the resonance of .3 mm thick quarts?' If you wanted to be cryptic you succeeded. |
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Chandra 'Hears' A Black Hole
Jan Panteltje responded to a press release:
If so, the B-flat pitch of the sound wave, 57 octaves below middle-C, would have remained roughly constant for about 2.5 billion years. Is it out of order to just write a frequency in Hz? Like nn Hz? (maybe float). At least I would have some idea. Middle C has a frequency of 261.63 Hz. The B-flat just below it has a frequency of 233.08 Hz. An octave is a doubling or halving of frequency, so 57 octaves below the B-flat just below middle C is 1.6 e-15 Hz, if I calculated correctly. That is a period of 618,307,825,964,715 seconds, or 19,592,992 years, again if I calculated correctly. Makes no sense to me. -- Jeff, in Minneapolis .. |
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Chandra 'Hears' A Black Hole
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Chandra 'Hears' A Black Hole
Jeff Root wrote:
Middle C has a frequency of 261.63 Hz. The B-flat just below it has a frequency of 233.08 Hz. An octave is a doubling or halving of frequency, so 57 octaves below the B-flat just below middle C is 1.6 e-15 Hz, if I calculated correctly. That is a period of 618,307,825,964,715 seconds, or 19,592,992 years, again if I calculated correctly. A bit generous with our precision, aren't we? Makes no sense to me. Well, sound waves are just longitudinal pressure waves through a medium, yes? In a sense, what this black hole is throwing out could be seen as such (as the original article stated, "ripples in the gas filling the cluster")... though a period of 19.6 million years seems to stretch the idea of "sound" to the breaking point. -=shrug=- -- -- With Best Regards, Matthew Funke ) |
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Chandra 'Hears' A Black Hole
Bob Officer replied to Jeff Root:
Middle C has a frequency of 261.63 Hz. The B-flat just below it has a frequency of 233.08 Hz. An octave is a doubling or halving of frequency, so 57 octaves below the B-flat just below middle C is 1.6 e-15 Hz, if I calculated correctly. That is a period of 618,307,825,964,715 seconds, or 19,592,992 years, again if I calculated correctly. Makes no sense to me. Sound = pressure waves = mechanical/kenetic energy... They are observing a periodic pressure wave... as the gases are flowing outward from the black hole. Calling such pressure waves Did you accidentally omit the word "sound" at this point? is not really accurate... Sound is a mechanical wave, so them calling this periodic wave sound is really reaching. I assume that they know what sound is and what it isn't. Since they call it "sound", I assume it is a correct use of the term. What makes no sense to me is: How can it have a period of 19 million years? -- Jeff, in Minneapolis .. |
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Chandra 'Hears' A Black Hole
Jeff Root wrote:
What makes no sense to me is: How can it have a period of 19 million years? Do you know of something that would keep it from having such a period? I'd be interested in how they measure the waves' speed of propagation. Once you have *that*, and you can see the ripples (which the article states Chadra "saw"), it seems to me that determining the period is trivial. The animations at the following URL might help you visualize how these ripples propagate, though I'm still trying to look up the physics behind the matter: http://www1.msfc.nasa.gov/NEWSROOM/news/video/2003/video03-152.html This link will show you photographs where they determine the ripples are located: http://www1.msfc.nasa.gov/NEWSROOM/news/photos/2003/photos03-152.html -- -- With Best Regards, Matthew Funke ) |
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Chandra 'Hears' A Black Hole
Matthew F Funke wrote:
This link will show you photographs where they determine the ripples ^^^^^^^^^^^^^^^^^ Whoops! Make that "photographs *of* where". -- -- With Best Regards, Matthew Funke ) |
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Chandra 'Hears' A Black Hole
The Reuters article had some additional information that is helpful to this
discussion: 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. http://www.cnn.com/2003/TECH/space/0...eut/index.html 1. I think that the scientists observed the 30,000 light year ripples, estimated the velocity of sound in the gas, and deduced the frequency. 2. Although a stretch, I do think they can technically classify this as sound. The definition of according to Merriam Webster: "mechanical radiant energy that is transmitted by longitudinal pressure waves in a material medium (as air) and is the objective cause of hearing". These are pressure waves in a gas, so if you were in the cosmic gas, could hear that low, and could live for 20 million years to listen to the entire period, then sure, you would hear sound. =) |
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