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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

#21

Post by russdill »

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 :)

That's assuming they are "naked" and not surrounded by rotating disks of gas and dust.

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

#22

Post by [deleted] »

spuz wrote: post #20
solipsism wrote: post #13

Earlier quoted context omitted.

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…

[deleted]

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

#23

Post by T-A »

spuz wrote: post #19
evanb wrote: post #12

Earlier quoted context omitted.

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?

If you accelerate an electric charge, it emits electromagnetic waves. If you accelerate a mass, it emits gravitational waves.

Two masses orbiting their common center of gravity are undergoing centripetal acceleration, so they continuously emit gravitational waves, spiraling closer as they lose energy (that's how the emission of gravitational waves was originally confirmed [1]).

[1] https://www.nobelprize.org/nobel_prizes/physics/laureates/19...

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

#24

Post by mstade »

raverbashing wrote: post #10

Interesting This was a couple of days days before Virgo got online AND one of the Ligo detectors was undergoing a noise modelling test (its mirrors were being vibrated at the time)

So no second opinions then, it could just as well be noise?

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

#25

Post by merraksh »

Six black hole merges observed in ~2 years! That's quite interesting. More observations will make for some useful statistical study.

I wonder if this would give us any insights w.r.t. matter and its distribution across the Universe, and/or help us better understand/estimate dark matter/energy.

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

#26

Post by Simon_says »

libeclipse wrote: post #18

> ...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.

Well, yea - that's what they mean when they say "1 solar mass".

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

#27

Post by lou1306 »

dwaltrip wrote: post #11
sulam wrote: post #6

Earlier quoted context omitted.

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...

You are correct. In fact, Einstein predicted gravitational waves but considered them un-observable, and the LIGO interferometer is 1km long exactly to magnify the effect.

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

#28

Post by T-A »

merraksh wrote: post #25

Six black hole merges observed in ~2 years! That's quite interesting. More observations will make for some useful statistical study. I wonder if this would give us any insights w.r.t. matter and its distribution across the Universe, and/or help us better understand/estimate dark matter/energy.

Dark matter, quite possibly:

https://astrobites.org/2017/08/31/could-dark-matter-be-black...

http://aasnova.org/2017/09/27/can-ligo-find-the-missing-dark...

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

#29

Post by mirimir »

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…

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

OK, that makes sense (for whatever that's worth).

But from the article:

> ... the latest discovery was produced by the merger of two relatively light black holes, 7 and 12 times the mass of the sun ... 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.

And you say:

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

I think that I get it. It's just that the stated masses of the merging black holes (7 and 12 solar masses) include gravitational potential energy. So the rest masses of the black holes didn't change, just their gravitational potential energy.

Yes?

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

#30

Post by evanb »

spuz wrote: post #19
evanb wrote: post #12

Earlier quoted context omitted.

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?

The answer is "by the processes of general relativity". When things fall "down" their potential energy is lowered, so they get faster. When mass-energy accelerates it emits gravitational waves, in much the same way when an electron accelerates it emits electromagnetic waves. If you're satisfied that a radio works by sloshing electrons around, you should be satisfied that a black hole merger emits radiation by sloshing mass around.

Where did the photons "come from"? Well, they weren't stored "inside" the electrons. By what process were the photons generated? Electrons accelerating radiate. That's essentially the answer. You can "math it up" if you want. It's not exactly an axiom, but it's pretty close to the bottom.

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