Posted on 08/14/2009 9:31:19 AM PDT by HIDEK6
Astronomers have detected the deepest note ever generated in the cosmos, a B-flat flying through space like a ripple on an invisible pond. No human will actually hear the note, because it is 57 octaves below the keys in the middle of a piano.
The detection was made with NASA's Chandra X-ray Observatory and announced at a press conference today.
The note strikes an important chord with astronomers, who say it may help them understand how the universe's largest structures, called galaxy clusters, evolve. The sound waves appear to be heating gas in the Perseus galaxy cluster, some 250 million light-years away, potentially solving a longstanding mystery about why the gas surrounding this cluster and others does not chill out as existing theory predicts.
The gas is apparently dancing excitedly to the eons-long drone of a deep B-flat.
Black hole music
Astronomers were not surprised to find the supermassive black hole making a strong sub-bass sound. Though these greatest known matter sinks are by nature dark and invisible, they create bright and chaotic environments in which many forms of radiation -- from radio waves to visible light to X-rays -- have been recorded. These electromagnetic waves all travel at the speed of light.
Sound waves are similar, but they travel far more slowly and are more physical in nature. Sound you hear, for example, can be produced by the visible compression and expansion of a stereo speaker. The waves physically compress the stuff through which they move, be it air, water, or hot interstellar gas.
Other studies have shown that the riotous activity around black holes -- where gas is accelerated to nearly light-speed -- produces many notes that are, all together, much like music. Collectively, the cosmos produce, scientists believe, a cacophonic symphony of inaudible tunes.
Musical production appears to be ubiquitous in Nature. Scientists often call it flicker noise, and it has also been detected in the X-ray outputs of magnetic fields within our solar system. Even Earth hums its own tune. Musical analogies are found in everything from seascapes to brainwaves.
Way out of range
The 53 hours of Chandra observations revealed a note that is more than a million billion times deeper than what you can hear.
"We have observed the prodigious amounts of light and heat created by black holes," said Andrew Fabian of the Institute of Astronomy in Cambridge, England, and leader of the study. "Now we have detected the sound."
"The Perseus sound waves are much more than just an interesting form of black hole acoustics," said Fabian's colleague Steve Allen. "These sound waves may be the key in figuring out how galaxy clusters grow."
Scientists had previously observed large amounts of hot gas infusing clusters. Given what's known, the gas should cool over time, however. Cooler gas would create areas of lower pressure near the center of a cluster, causing fringe gas to fall inward. In the process, trillions of stars would form.
This isn't what astronomers see when they look at clusters, though.
The Perseus cluster is the brightest known in X-rays, making it a good target for study. It has two large, bubble-shaped cavities that extend away from a central black hole. The cavities are formed by jets of material ejected from the black hole's surroundings, and the jets have been suspected of heating the outlying gas. But scientists couldn't see how.
A special image-processing technique was used to bring out subtle changes in brightness that revealed the presence of ripples -- the sound waves.
Fabian and Allen figure the sound waves, observed spreading out from the cavities, heat the gas. The amount of energy involved is staggering, equal to what would be produced if 100 million stars exploded.
A single, long-sounding note is produced by a sound wave in which the waves are the same size and shape continuously. The newfound note has been sounding, the researchers say, for about 2.5 billion years.
Caption:"The Chandra data show sound waves rippling through hot gas that fills the Perseus cluster. The features were discovered by using a special image-processing technique to bring out subtle changes in brightness."
"Is this image you are talking about a simple time lapse image acquired over the 53 hours; or is it more like a race track photo finish image?"
53hr shutter speed on an object ~250Mly away...
Even though the shutter speed is 53hrs, there is no motion to be observed. The time lapse is needed to gather spacial info. 2.5Byrs of event is contained in that still.
I would note that the ripples are not concentric and diminish abruptly rather than with distance. I don't see yet how one can associate this image with a wave generator. I also don't see how you come up with a velocity for the "signal" being suggested.
ML/NJ
Yes.
" I just am not familiar with the use of the word ripple as a scientific term."
It's English and portrays waves through a fluid cross section very well. The fluid in this case is a gas embedded in a field of galaxies.
"I would note that the ripples are not concentric and diminish abruptly rather than with distance."
The entire assembly appears to have a 2.5Bly radius. The lack of concentricity is caused by spacial inhomogeneitiesous in the gas and resultant speed of sound variation, and rotational effects. There's no apparent dissipation, because the density peaks in the longitudinal waves are substantial and gravity will maintain that configuration. Pressure waves through gas regions generate stars.
The generating wave is a resultant og the BH's gas jet. If the ejecta moved at c, there would be 120 ripples. Since there are only ~5.5 ripples/radius, the ejecta, or speed of sound in the gas, is 0.05c.
Well, now that I think about it we did use "ripple tanks" in my high school physics class (PSSC - it was pretty good) to study waves.
The entire assembly appears to have a 2.5Bly radius.
And how do you know this?
ripples/radius
What kind of a unit is this? Radius of what?
Since there are only ~5.5 ripples/radius, the ejecta, or speed of sound in the gas, is 0.05c.
I don't understand. Does the number 5.5 come from the number of wavelengths extending from the generating object? I still don't understand why these peaks(?) don't extend out indefinitely from the center. How do you infer a wave velocity from any of this?
ML/NJ
"And how do you know this?"
The NASA guys said so.
"Radius of what?"
That Persius cluster. The gas cloud is embedded in the galaxies. That's the same as saying the galaxies are embedded in the gas cloud. Both are the Persius cluster which has the radius of 2.5Bly.
"I still don't understand why these peaks(?) don't extend out indefinitely from the center."
There's nothing but intergalatic space outside the Persius cluster. That means there's nothing to propagate a longitudinal shock/sound wave through.
"Does the number 5.5 come from the number of wavelengths extending from the generating object?
Yes.
"How do you infer a wave velocity from any of this?"
If the jet v was c, there would be 120 ripples. There is only ~5.5, so... 5.5/120=0.05c.
don’t think sound waves, think math
... Also, the BH jets would have had a startup time in the cluster.
Any one that can understand what you wrote is either a genius or schzoid...I am not a genius..
Closer to home...
Somewhere I found a geologic _audio_ recording of the Indonesian Christmas Eve Tsunami. Fascinating sound - with sub-bass so strong it blew out my iPod headphones.
ML/NJ
Here's a paper that covers the matter: A deep Chandra observation of the Perseus cluster: shocks and ripples" Fig 5 gives a radius of 163kly. The shock/sound velocity is ~0.005-0.02c.
This discussion the two of you are having is above my pay grade. WAY above my pay grade. But the fact that you’re having this discussion at all has me more encouraged about the future of FR than anything I’ve read here for quite a while. Hope you don’t mind me peeking in the window from time to time just because I enjoy seeing IQ points flying around a room.
ML/NJ
I just heard about this from my daughter, googled it up and found it here, and thought you might be interested in it.
Job 38:6-8
6 On what were its footings set,
or who laid its cornerstone-
7 while the morning stars sang together
and all the angels shouted for joy?
8 “Who shut up the sea behind doors
when it burst forth from the womb,
Okay, I just did a little research on your links, and the legendary, “Brown Noise.”
I didn’t know that they actually tested this theory on Mythbusters.
LOL!!
Without checking it out for myself, I’ll tell you how to do it -
an octave is a doubling of frequency.
So take the frequency of the “middle B flat” and double it 40 times (times 2 to the 40th power) and compare that to the frequency of yellow.
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