Four more Gravitational-Wave Events Announced on 1st Dec, 2018

Gary Roberts
Gary Roberts
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Topic 217153

This very recent announcement brings the total number of gravitational-wave detections announced so far to eleven - ten binary black hole mergers and one involving neutron stars.

What struck me is that the four latest announcements and two previously announced events all occurred in less than a month, between 29th July and 23rd August 2017.  One of the newly announced events was both the most massive and the most distant.  The resultant black hole was approximately 80 solar masses and that's after losing nearly 5 solar masses worth of energy to gravitational radiation.  The event occurred approximately 5 billion light years from the detectors.

Mind boggling stuff! :-).

I found this announcement by accident.  I was just having a quick browse of the science stuff on Ars Technica and there it was at the top of the list.  If you look at the actual Ars article, it contains a short video simulation showing the waveform of the detected signals from all the 10 BH-BH mergers announced so far.  In some cases the sizes of the two merging objects are quite different from each other.



Joined: 22 Jan 05
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A catalogue of GW events was

A catalogue of GW events was announced in Italy by the Istituto Nazionale di Fisica Nucleare which manages the Virgo interferometer at Cascina. Why  GW research is explored in Italy by the INFN is due to Edordo Amaldi's interest in GW after a visit to  Joseph Weber's laboratory.

Mike Hewson
Mike Hewson
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Thank you Gary, I had not

Thank you Gary, I had not known of this. :-0

Couple of points :

- I'm fascinated by the aspect that 2 + 2 is not equal to four here. If you want to keep conservation of mass/energy then you have to believe Einstein. Gravitational radiation just has to exist ie. predominantly non-electromagnetic energy leaving the collision site. So the mass of the final hole is always less than the sum of the progenitors.

- for me at least, each detection ( say, by implying an upper limit on graviton rest mass ) adds to evidence that GR cannot be quantised. We may say that QM is not needed to predict behaviour at a GW source, that is then deduced at a distance using a classical theory. GR covers it all. QM and GR can't both be right when referring to the one object. The only escape from this conundrum is to postulate something else, previously not thought of, to explain the scale dependence of these theories ( QM in the small, GR in the large ). 

- speaking of Albert, he would be thrilled to bits to know of this were he alive. He knew of the GW prediction not long after his GR theory was finalised. He despaired of ever finding them due to the small magnitude of the signal.

- so why

Most notably, we find that almost all black holes formed from stars are lighter than 45 times the mass of the Sun."

is this a significant comment? Amongst other things, it tells you something about the population of stars that go down the pathway to form BHs. Some of these detections refer to events occurring a substantial fraction of the universe's age ago. There were really big stars forming early on in the universe that had to lose mass before contracting to sufficient density to form an event horizon. These first generation stars must have been quite a sight, but not for too long. The bigger they are the brighter and the quicker is the thermonuclear burn rate. Radiation pressure alone would clear out their neighbourhood's of material and thus limit their maximum size from any further accretion. To flip the viewpoint : any theory of star formation has to account for this finding.

Cheers, Mike.

I have made this letter longer than usual because I lack the time to make it shorter ...

... and my other CPU is a Ryzen 5950X :-) Blaise Pascal

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Hallo! did

Hallo! did report about this on Dec. 3rd 2018 (German language).

The preprint of the according scientific paper you find here, that shows some more interesting details.

It´s realy amazing!

Kind regards and happy crunching




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