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LIGO and Virgo announce the detection of a black hole binary merger

ligo.caltech.edu

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Re: LIGO and Virgo announce the detection of a black hole binary merger

#11

Post by dwaltrip »

sulam wrote: post #6
spuz wrote: post #2

One question I've had about gravitational wave detections that I haven't yet been able to find an answer to is what is the mechanism by which the mass of an orbiting black hole pair converts its mass into a gravitational wave? Presumably the mass of the black holes is comprised of matter (in whatever form that may be) and kinetic energy. Is the gravitational wave energy while the two objects orbit purely a conversion…

Mass is energy. As I understand it, the waves are created because of the rapid acceleration of large masses, either black holes or neutron stars. These waves do transmit energy and the final resulting body will be less massive at least partially because of that.

I believe all accelerating masses emit gravitational waves, but that most do so on an absurdly small scale. As if the 10^-20 scale of the black hole merger gwaves isn't small enough...

Re: LIGO and Virgo announce the detection of a black hole binary merger

#12

Post by evanb »

spuz wrote: post #2

One question I've had about gravitational wave detections that I haven't yet been able to find an answer to is what is the mechanism by which the mass of an orbiting black hole pair converts its mass into a gravitational wave? Presumably the mass of the black holes is comprised of matter (in whatever form that may be) and kinetic energy. Is the gravitational wave energy while the two objects orbit purely a conversion…

When an apple falls to the earth, by what process is its potential energy converted to kinetic energy? Gravitational processes alone.

Apple-earth collisions primarily radiate apple sauce, black hole mergers primarily radiate in gravitational energy.

Minor nit: In general relativity black holes are not actually comprised of matter---they're entirely warping of spacetime. Whether that remains true in a quantum theory of gravity is unknown.

Re: LIGO and Virgo announce the detection of a black hole binary merger

#13

Post by solipsism »

spuz wrote: post #2

One question I've had about gravitational wave detections that I haven't yet been able to find an answer to is what is the mechanism by which the mass of an orbiting black hole pair converts its mass into a gravitational wave? Presumably the mass of the black holes is comprised of matter (in whatever form that may be) and kinetic energy. Is the gravitational wave energy while the two objects orbit purely a conversion…

Anything spinning in an asymmetrical way (e.g. two bodies orbiting each other, but not a single body spinning) loses angular momentum as gravity waves. This is true whether it's two black holes or a tumbling dumbbell.

In addition to that, the ultimate merger of the black holes releases the incredible amount of gravitational potential energy that existed between them when they were separate bodies.

No mass escapes the event horizon. These are black holes after all :)

Re: LIGO and Virgo announce the detection of a black hole binary merger

#14

Post by krylon »

dwaltrip wrote: post #9
krylon wrote: post #8

Earlier quoted context omitted.

Huh. IIRC, black hole mergers are also a likely source of short gamma ray bursts. So I suspect at 1 AU, one would need a lot of shielding to not get fried by the gamma rays. EDIT: What I meant to say was: It would probably be quite awesome to experience such an event up close, provided it is possible to do so safely. ;-)

I believe that black hole mergers are dark in the entire electromagnetic (EM) spectrum. This is why the recent binary neutron star merger was so groundbreaking -- it emitted both gravitational waves and a broad spectrum of EM waves. Indeed, though, it would be awesome to witness the collision and resulting gwaves personally, if such a thing was possible :)

> I believe that black hole mergers are dark in the entire electromagnetic (EM) spectrum.

Now that I think about it - yes, of course. It's why they are called _black_ holes. ;-) facepalm

Re: LIGO and Virgo announce the detection of a black hole binary merger

#15

Post by vecter »

krylon wrote: post #14
dwaltrip wrote: post #9

Earlier quoted context omitted.

I believe that black hole mergers are dark in the entire electromagnetic (EM) spectrum. This is why the recent binary neutron star merger was so groundbreaking -- it emitted both gravitational waves and a broad spectrum of EM waves. Indeed, though, it would be awesome to witness the collision and resulting gwaves personally, if such a thing was possible :)

> I believe that black hole mergers are dark in the entire electromagnetic (EM) spectrum. Now that I think about it - yes, of course. It's why they are called _black_ holes. ;-) facepalm

That doesn't follow from the fact that black holes are "black". For example, black holes can emit a ton of radiation from accretion disk as matter accelerates and falls inwards, radiating huge amounts of energy [0]. Two naked black holes merging probably wouldn't emit much (if any) EM radiation, but if they had very active accretion disks, then it's certainly possible there would be a ton of EM activity.

[0] https://en.wikipedia.org/wiki/Accretion_disk

Re: LIGO and Virgo announce the detection of a black hole binary merger

#16

Post by pja »

krylon wrote: post #3

> Dubbed GW170608, the latest discovery was produced by the merger of two relatively light black holes, 7 and 12 times the mass of the sun, at a distance of about a billion light-years from Earth. The merger left behind a final black hole 18 times the mass of the sun, meaning that energy equivalent to about 1 solar mass was emitted as gravitational waves during the collision. I wonder if one would experience any macr…

I ask because one solar mass worth of energy sounds like ... a lot. At least to me as an astronomical layperson.

It’s a ridiculously large amount of energy. Someone might want to check my numbers, but a standard candle Type 1A supernova releases ~2x10^44 Joules. 1 Solar mass energy is equivalent to roughly ~2x10^47 Joules. So this black hole merger is about 1000x times the energy released by an ordinary supernova. And there’s nothing ordinary about a supernova, pace https://what-if.xkcd.com/73/

Re: LIGO and Virgo announce the detection of a black hole binary merger

#17

Post by raverbashing »

dwaltrip wrote: post #9
krylon wrote: post #8

Earlier quoted context omitted.

Huh. IIRC, black hole mergers are also a likely source of short gamma ray bursts. So I suspect at 1 AU, one would need a lot of shielding to not get fried by the gamma rays. EDIT: What I meant to say was: It would probably be quite awesome to experience such an event up close, provided it is possible to do so safely. ;-)

I believe that black hole mergers are dark in the entire electromagnetic (EM) spectrum. This is why the recent binary neutron star merger was so groundbreaking -- it emitted both gravitational waves and a broad spectrum of EM waves. Indeed, though, it would be awesome to witness the collision and resulting gwaves personally, if such a thing was possible :)

Nah I think there are some effects in the visible range. You probably have some kind of accretion disk that gets shaken up by the merger, there might also be some effects due to Hawking radiation

But they're probably only visible from close range (like the 1AU mentioned above) and are too faint to be seen from 1Bi light years like the event that they captured

Re: LIGO and Virgo announce the detection of a black hole binary merger

#18

Post by libeclipse »

> ...meaning that energy equivalent to about 1 solar mass was emitted as gravitational waves during the collision.

Damn. That's something like 179 100 000 000 000 000 000 000 000 000 000 000 000 000 000 000 J

That's an insane amount of energy. It's equivalent to what you would get if you converted the entire mass of the sun into pure energy.

Re: LIGO and Virgo announce the detection of a black hole binary merger

#19

Post by spuz »

evanb wrote: post #12
spuz wrote: post #2

One question I've had about gravitational wave detections that I haven't yet been able to find an answer to is what is the mechanism by which the mass of an orbiting black hole pair converts its mass into a gravitational wave? Presumably the mass of the black holes is comprised of matter (in whatever form that may be) and kinetic energy. Is the gravitational wave energy while the two objects orbit purely a conversion…

When an apple falls to the earth, by what process is its potential energy converted to kinetic energy? Gravitational processes alone. Apple-earth collisions primarily radiate apple sauce, black hole mergers primarily radiate in gravitational energy. Minor nit: In general relativity black holes are not actually comprised of matter---they're entirely warping of spacetime. Whether that remains true in a quantum theory o…

None of this actually answers the question. The question is by what process does energy in the binary black hole system get converted into gravitational wave energy?

Re: LIGO and Virgo announce the detection of a black hole binary merger

#20

Post by spuz »

solipsism wrote: post #13
spuz wrote: post #2

One question I've had about gravitational wave detections that I haven't yet been able to find an answer to is what is the mechanism by which the mass of an orbiting black hole pair converts its mass into a gravitational wave? Presumably the mass of the black holes is comprised of matter (in whatever form that may be) and kinetic energy. Is the gravitational wave energy while the two objects orbit purely a conversion…

Anything spinning in an asymmetrical way (e.g. two bodies orbiting each other, but not a single body spinning) loses angular momentum as gravity waves. This is true whether it's two black holes or a tumbling dumbbell. In addition to that, the ultimate merger of the black holes releases the incredible amount of gravitational potential energy that existed between them when they were separate bodies. No mass escapes the…

How much of the 1 solar mass of detectable gravitational energy is released before the moment of collision and how much is released at the moment of collision? Is the mechanism for release of this energy the same in both cases? If 1 solar mass of energy was released in total, and the mass of the combined black hole is less than the two before the merger, how is it possible that none of the mass of the black holes has escaped their respective event horizons?
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