The Sound of a Black Hole

Snags writes "Astronomers have used the Chandra X-ray Observatory to observe the deepest, lowest-frequency sound waves ever observed. By my calculations, the 'B-Flat 57 octaves below middle-C' has a period of 9.8 million years. Despite arguments that explosions in space movies should be silent, it is legitimate to call these sound waves because at that frequency, particles of space dust can 'see' each other through gravity. These notes are 'over a million billion times deeper than the limits of human hearing', so to call it infra-sound would be a bit of an understatement."

Comments

That explains!

[orkysoft]

Infrasound! Now that explains why many people have this irrational fear of black holes! :-)

My vivid imagination...

[Anonvmous Coward]

When I read "The Sound of a Black Hole"
the sound I heard in my mind was "oh shit there's a black hole!"

Wow - and I thought Germany had a long concert

[MerlynEmrys67]

bbc.co.uk

So this is a 639 year concert that has started in Germany. The concert has been ongoing for 17 months (the initial "quiet period" of the organ filling) however the first three note chord has been hit.

Boy wish I had that kind of time to waste... Imagine the monks 630 years from now going - "Well, this is over now - what the hell are we going to do now ?"

Re:Wow - and I thought Germany had a long concert

[menscher]

"The performance follows a legal case in which composer Mike Batt was forced to pay a six-figure sum to Cage's publishers, who accused him of plagiarising a silent piece of music." And we thought SCO was bad!

This would be a "RTFA". It *is* sound.

[JeanPaulBob]

Read the Space.com link.

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.

They're not saying that infra-radiation is sound--they used the telescope to see ripples in the gas. That's the sound.

GSS

[falsification]

B-Flat 57 octaves below middle-C

AKA "a giant sucking sound."

B-Flat 57 octaves below middle-C?

[Anonymous Coward]

B-Flat 57 octaves below middle-C, and it's the sound of a black hole. My , they've discovered the brown note!

Umm, sorry for that...

No matter.

[bobdotorg]

My extreme audiophile friend now has to replace his whole system to capture the experience of these new sounds.

Re:No matter.

[mlush]

My extreme audiophile friend now has to replace his whole system to capture the experience of these new sounds.

Make that replace his whole Star system.

Alien

[DeltaStorm]

In space no once can hear you hum...

Concert

[Molina the Bofh]

I wouldn't buy tickets to a music-playing blackhole concert. They suck.

Re:Concert

[danratherfan]

I don't know. I liked their one and only album "Songs from the Singularity".

Re:It is not sound

[recursiv]

I concede defeat.

On the team

[xiox]

I'm on the team that did this. Ask any questions you like!

Re:On the team

[FrostedWheat]

I'm on the team that did this. Ask any questions you like!

Would you like some toast?

-Talkie Toaster

Re:On the team

[xiox]

Good question. If you look at the ripple image (generated by unsharp masking), you'll see the waves aren't perfectly spaced, so there's an error there. We estimate a wavelength of about 11 kpc. You then need the sound speed, which is a function of temperature (about 1170 km/s in gas of about 5 keV). The calculation of the period of 10^7 years is probably a good estimate, but it isn't precise. If you're really interested in the details read the original paper here.

Re:On the team

[xiox]

Look, I don't want any toast, and he doesn't want any toast. In fact, no one around here wants any toast. Not now, not ever. No toast!

Or muffins! Or muffins! We don't like muffins around here! We want no muffins, no toast, no teacakes, no buns, baps, baguettes or bagels, no croissants, no crumpets, no pancakes, no potato cakes and no hot-cross buns and definitely no smegging flapjacks!

Do black holes exist?

[nimblebrain]

Black holes rely on an assumption that gravity has no limits on its strength, and to some extent on it following a strict Newtonian curve.

Thinking of "curves" in space-time is an interesting analogy for gravity, but still doesn't address the mechanism - sure, the planet may be on a "45 degree" incline in spacetime, but what forces it down... and not up? You would nearly have to posit the existence of some constant stream of gravitons coming at 'right angles' to three-dimensional space in order to actually push things 'down the well'.

There are alternate corpuscular (i.e. caused by particles; "quantum") models of the mechanism of gravity. There's the LeSagian model, with modern reworks that range from the bizarre-yet-possible theories of Tom Van Flandern, to the more "moderate" theories of Paul Stowe explaining how the "drag" factor that detractors expect doesn't show up, in exactly the sort of way that Feynman expressed it for electromagnetism.

The LeSage-type theories are, in general, "push" theories, which operate in a medium filled with gravitons (just as space is filled with photons) that are deflected/absorbed near bodies and cast 'shadows' that create a low "pressure" area close to surfaces and, to a lesser extent, between bodies.

The formulae calculate out approximately to Newton's/GR's gravity equation, but with some interesting exceptions:

• There is a stronger fall-off at greater distances, which limits the effective range of gravity (surprisingly, this reduces the need for 'dark matter' to keep galaxies in the shape they're in)
• Inside denser and denser bodies, graviton absorption reaches a point where matter on the inside hardly contributes at all (a complete gravity "shadow")

This upper limit on the strength of gravity may prevent the ultimate collapse that black hole theory requires.

Black holes are still a theoretical construct. Even the jets, now often taken as a 'sign' of a black hole, are still a largely unexplained phenomenon, one that is also associated with accretion disks for newly-forming stars.

So if something's singing in that cloud, it may not be as dense as it's accused of being.

I apologize for all the jargon. I shall go read another thread on SCO as just punishment :)

Re:Do black holes exist?

[Bonker]

Thinking of "curves" in space-time is an interesting analogy for gravity, but still doesn't address the mechanism - sure, the planet may be on a "45 degree" incline in spacetime, but what forces it down... and not up? You would nearly have to posit the existence of some constant stream of gravitons coming at 'right angles' to three-dimensional space in order to actually push things 'down the well'.

The best explantion for this I've ever heard deals entirely with special relativity and never touches quantum mechanics. The author I read (Epstein) discusses what he calls 'Slow Time'. An object is always moving in four dimenions, even if it appears at rest to an observer, because it is moving forward in time as well. Since all dimensions of space and time are warped by the presence of matter, and not just space, if the object being observed is closer to a source of gravity (on a steeper part of the curve of space-time), he will start to experience time shortening or time dialation sooner and more strongly than you, the observer. His straight-line path through time starts to curve toward the source of gravity. This time-dialation acts as a vector force to 'push' him towards the source of gravity.

You can read more about the interperatation of Special Relativity in this book: Relativity Visualized

Re:Do black holes exist?

[krysith]

Doesn't a stronger fall off at greater distances actually go against the data we have for anomalous gravitational effects? If anything, both cosmological ("dark matter") and experimental data point to gravity being stronger than Newton at long distances.

See also:
"Study of the anomalous acceleration of Pioneer 10 and 11", Anderson, J.D., Laing, P.A., Lau, E.L., Liu, A.S., Nieto, M.M., and Turyshev, S.G., Physics Review D, v65, 082004, (2002)

Re:This would be a "RTFA". It *is* sound.

[xiox]

That's right. We see the ripples as X-ray emission is very sensitive to gas density (goes like density squared), so we see the dense regions where the gas is being compressed by the sound wave. The picture is a "snapshot" as we never see the wave move.