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beecee

Sixth Gravitational Wave Discovery:

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https://www.ligo.caltech.edu/WA/news/ligo20171115

Scientists searching for gravitational waves have confirmed yet another detection from their fruitful observing run earlier this year. 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. 

 

more at link....

 

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2 hours ago, beecee said:

https://www.ligo.caltech.edu/WA/news/ligo20171115

Scientists searching for gravitational waves have confirmed yet another detection from their fruitful observing run earlier this year. 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. 

 

more at link....

 

does anyone know if gamma or x rays were detected here as well, giving clear evidence the gravity wave travels at light speed (or perhaps is induced by the gamma/x rays moving through space)

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7 hours ago, interested said:

does anyone know if gamma or x rays were detected here as well, giving clear evidence the gravity wave travels at light speed (or perhaps is induced by the gamma/x rays moving through space)

I assume not. As no such radiation is expected from black holes it would have been headlined. 

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2 hours ago, Strange said:

I assume not. As no such radiation is expected from black holes it would have been headlined. 

My old boss used to say "never assume anything unless you want to make an ass of u and me".  

Quoting from the link below ref gravity waves, there are others links on the subject also, but it has recently been shown gravity waves travel at light speed with a reasonable degree of certainty. ie they keep up with the gamma/x rays originating from the same source.

" However on August 17 a single merging event was detected that delivered all the puzzle pieces in one swoop, when for the first time a range of sophisticated equipment picked up a series of signals from two neutron stars colliding. These included a gravity wave, a ripple in the fabric of space time, detected by the famous LIGO and VIRGO observatories. The gravity wave was quickly found to nearly coincide with a burst of gamma rays from detected by the Fermi satellite. The observatories swiftly alerted a world-wide association of astronomers with access to a vast suite of telescopes and satellites capable of detecting cosmic light spanning the entire electromagnetic spectrum, from radio waves to high-energy gamma rays.

This equipment captured the light from a kilo-nova, a type of radioactive explosion produced in the collision and predicted by theory.  Two weeks later, the Chandra satellite detected high-energy X-rays consistent with a gamma ray burst, the most powerful kind of explosion in the universe, a signature of the birth of a black hole and the launch of a beam of material at speeds close to that of light.

"

http://www.bath.ac.uk/research/news/2017/10/16/first-light-gravity-wave/

(unrelated dark matter issue axioms dont exist either https://phys.org/news/2017-11-dark-narrowed.html?utm_source=nwletter&utm_medium=email&utm_campaign=daily-nwletter )

 

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On 11/17/2017 at 11:08 AM, Strange said:

Are the gravitational waves detected by ligo solely attractive are do they repel also. The readings do not make it clear. Most likely it is a increase in decrease in gravity attraction detected but then dark energy seems to repel?

  

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13 minutes ago, interested said:

Are the gravitational waves detected by ligo solely attractive are do they repel also. 

Neither. They are alternating compression/stretching at right angles to the direction of travel:

a03fig03.gif

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17 minutes ago, Strange said:

Neither. They are alternating compression/stretching at right angles to the direction of travel:

a03fig03.gif

Can gravitational waves be shown graphically in terms of spacetime geometry?

Is the rubber sheet  with radiating waves the only representation?

 

https://www.google.ie/search?hl=en&tbm=isch&source=hp&biw=1600&bih=769&ei=Kj4QWvOBBYHwaKWOp4AC&q=merging+blasck+hole&oq=merging+blasck+hole&gs_l=img.3...1561.7410.0.9403.0.0.0.0.0.0.0.0..0.0....0...1.1.64.img..0.0.0....0.FgoeW3WFcww   loads of them

 

Am I really just asking for a mathematical/geometric  analysis of a region of space as a ripple passes through and would that just be another  example of spacetime being  minutely curved -this time  as a result of an extremely distant event ?

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12 minutes ago, geordief said:

Can gravitational waves be shown graphically in terms of spacetime geometry?

I guess you can think of the vertical component of the wave representing the strain (stretching and compression) in that direction. It is hard to imagine how you would visualise the sideways strain at the same time.

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13 minutes ago, Strange said:

I guess you can think of the vertical component of the wave representing the strain (stretching and compression) in that direction. It is hard to imagine how you would visualise the sideways strain at the same time.

Would there be a time axis in that  representation (I am quite happy to forego the y- and z-axes if it means time (or ct ,perhaps)  can be depicted  in relation to  a spatial distance  in a graphical or geometrical way.

 

Pardon my  ignorance but this vertical/ horizontal   feature of the wave has nothing to do  with the e and m components of an em wave? (it looks a bit similar-is that a feature of all waves)

 

What causes these vertical/horizontal components in a gravitational waves? (is  it only evident in the inter spatial relations?)

Edited by geordief

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4 minutes ago, geordief said:

Would there be a time axis in that  representation (I am quite happy to forego the y- and z-axes if it means time (or ct ,perhaps)  can be depicted  in relation to  a spatial distance  in a graphical or geometrical way.

I think it would be a static snapshot - there are some videos that animate the ripples radiating away. That would be the time dimension. I don't know if there is also some distortion in the time dimension.

Quote

Pardon my  ignorance but this vertical/ horizontal   feature of the wave has nothing to do  with the e and m components of an em wave? (it looks a bit similar-is that a feature of all waves)

You are right: it is just characteristic of waves. They all happen to be sine curves (or close approximations to sine).

Quote

What causes these vertical/horizontal components in a gravitational waves? (is  it only evident in the inter spatial relations?)

Good question ... Very good question ...

We might need a Mordred to answer that!

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A GW wave is a superposition of 10 waves, the only two waves are the Tranverse and traceless wave components. Hence GW waves being in the transverse traceless gauge. These two waves have a 45 degree phase shift from each other. This corresponds to the H positive and cross polarizations in image above. Also the quadrupole moment. spin 2 characteristic 

Edited by Mordred

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40 minutes ago, Mordred said:

A GW wave is a superposition of 10 waves, the only two waves are the Tranverse and traceless wave components. Hence GW waves being in the transverse traceless gauge. These two waves have a 45 degree phase shift from each other. This corresponds to the H positive and cross polarizations in image above. Also the quadrupole moment. spin 2 characteristic 

Not that I have a hope of gleaning anything from this ,but is this  a decent description? It seems to date from pre-Ligo times....(I googled it based on your post) 

 

http://eagle.phys.utk.edu/guidry/astro616/lectures/lecture_ch21.pdf 

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On 11/17/2017 at 5:08 AM, Strange said:

Thanks Strange!

I was planning to ask the question. Is there any scenario where we would have a visible component of a black hole merger? I haven't read the article yet but I am a fan of Ethan Siegel and I am sure he will give a fine explanation.

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11 minutes ago, Outrider said:

Is there any scenario where we would have a visible component of a black hole merger?

I think only if there were significant accretion disks. I'm not sure if/why that is considered unlikely for merging binaries. 

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6 minutes ago, Strange said:

I think only if there were significant accretion disks. I'm not sure if/why that is considered unlikely for merging binaries. 

I was thinking along the same lines. Perhaps the accretion disks get ripped off before the black holes get close enough to produce gravitational waves? Just a WAG.

How bout a neutron star and a black hole? Is that even considered a merger or just lunch?:)

I'll let you know what I think of the article after I read it. To much distraction to read it at work. Reading ES reminds me of what an old man told me along time ago. "Its important to listen to every word."

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Well I read the article and it was a good read but I don't think it really addressed why black hole mergers might not have an EM component. In fact the article states that several researchers feel that there was one but their findings cannot be confirmed. 

He concludes with four bullet points that the evidence seems to suggest that if black hole mergers do have an EM component , it's one that's:

  • incredibly weak,
  • that occurs mostly at lower energies,
  • that doesn't have a bright optical or radio or gamma-ray component,
  • and that occurs with an offset to the actual emission of gravitational waves.

He also dosent get into the why of the offset. I dont understand that either.

The article left me with another question. Sorry. I'll repost your link to (hopefully) avoid confusion. 

https://www.forbes.com/sites/startswithabang/2017/06/08/newest-ligo-signal-raises-a-huge-question-do-merging-black-holes-emit-light/#680a220147d9

Quote

According to our best models of physics, merging black holes aren't supposed to emit any light at all. A massive singularity surrounded by an event horizon might emit gravitational waves, due to the changing curvature of space time as it orbits an inspirals with another giant mass, in line with General Relativity's predictions. Because that gravitational energy, emitted as radiation, needs to come from somewhere, the final black hole post-merger is about two solar masses lighter than the sum of the originals that created it. This is completely in line with the other two mergers LIGO observed: where around 5% of the original masses were converted into pure energy, in the form of gravitational radiation.

Did he just say something came out of a black hole? 

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26 minutes ago, Outrider said:

Well I read the article and it was a good read but I don't think it really addressed why black hole mergers might not have an EM component.

There is no matter involved in a merger of "just" two black holes and so nothing to generate Em radiation. But if there is an accretion disk, then that could be affected in such a way as to generate radiation; but even this might require more than our current theories to explain it (I really don't know).

29 minutes ago, Outrider said:

He also dosent get into the why of the offset. I dont understand that either.

I think because of the size of the accretion disk that would generate it.

30 minutes ago, Outrider said:

Did he just say something came out of a black hole? 

Interestingly, he touched on this in another blog. The energy for the gravitational waves comes from the system: the extremely stirred up spacetime between the black holes.

https://www.forbes.com/sites/startswithabang/2017/11/10/ask-ethan-could-matter-escape-the-event-horizon-during-a-black-hole-merger

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Thanks for the replies they really help.

34 minutes ago, Strange said:

There is no matter involved in a merger of "just" two black holes and so nothing to generate Em radiation. But if there is an accretion disk, then that could be affected in such a way as to generate radiation; but even this might require more than our current theories to explain it (I really don't know).

Ok I guess we are just going to have to wait for more observations. 

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5 minutes ago, Outrider said:

Thanks for the replies they really help.

Thanks. (I have had a few negative reactions to my answers recently so it is reassuring to know I can still be useful occasionally!)

 

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2 minutes ago, Strange said:

Thanks. (I have had a few negative reactions to my answers recently so it is reassuring to know I can still be useful occasionally!)

 

Your welcome. I'll probably have a little more to say and possibly more questions after I think about your article a little more.

Honestly, with regard to the two threads I think you are referencing, after page three or four I don't know why you bothered.

Carl Sagan ignited my interest many years ago with his series of books chronicling the adventures of the pioneer probes almost thirty years ago. I am still very much hooked. As I don't have the formal training I rely on people like you to explain the finer details of the amazing discoveries being made these days.

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1 hour ago, Outrider said:

Carl Sagan ignited my interest many years ago with his series of books chronicling the adventures of the pioneer probes almost thirty years ago.

Should be voyager probes.

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