Observation of Gravitational Waves from a Binary Black Hole Merger

[Eratosthenes (Peter)]

Originally Posted by xelasnave

Could the wave trigger star formations or other events within any range relatively close to the merger.

interesting notion. Waves have valleys and peaks and points of inflection. One would assume that any nearby dust and gas will be effected in various ways. Gathered and carried along perhaps? Concentrated into the seeds of future stellar or galactic structures??

I recall reading that the two black holes that are spinning around one another are 29 and 36 solar masses. When they combine they will produce one black hole with an estimate mass of 62 solar masses.

There are 3 solar masses which are channeled elsewhere - will most of this massive energy end up powering the gravitational wave?

In any case these pulses of Hades are supremely powerful, especially close to the source.

I would like to see another LIGO type detector constructed - preferably in Australia with evacuated tubes over 100km long and arranged in a Crucifix geometry.

[xelasnave]

I thought if we looked past the merged black hole (behind it) we may be able to observe close stars say one light year "respond" to the passing wave. Looking behind may show something. The event was say 1.3 billion light years so if we observe something 1.3 billion light years plus one light year next September we maybe see it pass by that object.
But I see new links that I must read.

[Eratosthenes (Peter)]

Originally Posted by xelasnave

I thought if we looked past the merged black hole (behind it) we may be able to observe close stars say one light year "respond" to the passing wave. Looking behind may show something. The event was say 1.3 billion light years so if we observe something 1.3 billion light years plus one light year next September we maybe see it pass by that object.
But I see new links that I must read.

one year later in a 1.3 billion year time frame is a very small percentage ~0.0000000769 %

What do you expect to extract and delineate from a measurement in September 2016?

The signal was already very faint in September 2015 - and that signal was most likely the peak of the wave - ie one of the initial wave pulses

Unless some sort of pre-event has been measured and there is something bigger yet to reach us.?

[xelasnave]

I have no idea of the possible effect.
Say there is a star or other object one light year past our event if there is anything to observe we could make the observation next September.If there was an object close behind we would see that event after last September.

[xelasnave]

the percentage is irrelevant but it may be we could observe effects behind which will not reach us until a future time.

[bojan]

Alex,
have a look at the link below to get some feeling about what the effect of the GW source in question is on "distant" object:
http://gizmodo.com/your-questions-ab...red-1758269933

I was surprised myself when I've read it.

"How far away do you have to be from this kind of black hole merger to live to tell the tale?
Stuver: For the black hole binary we detected with gravitational waves, they produced a maximum change in the length of our 4 km (~2.5 mi) long arms [of] 1x10-18 meters (that is 1/1000 the diameter of a proton). We also estimate that these black holes were 1.3 billion light-years away.
Now assume that we are 2 m (~6.5 ft) tall and floating outside the black holes at a distance equal to the Earth’s distance to the Sun. I estimate that you would feel alternately squished and stretched by about 165 nm (your height changes by more than this through the course of the day due to your vertebrae compressing while you are upright). This is more than survivable."

The above quotation summarizes the issue of noticeability.. provided the calculation involved was correct.

[xelasnave]

Thank Bojan.
That's cleared it up for me.
Surprising indeed.

[torsion (Bram)]

Hi bojan,

As for the interaction to measure the gravitational wave, because gravitational waves have such a weak coupling with matter, that is what made the measurement so incredible difficult.

Weber's principle idea was that the gravitational wave would 'ping' one of the resonant modes of the bar, and then he would readout the 'energy/displacement' of that resonance. That made these bar detectors 'resonant bar detectors', looking at gravitational waves around 1000 Hz (actual frequency depends on the resonant mode of the bar). The signal could be followed for maybe 10 Hz to 20 Hz, and then disappeared in the noise.

The LIGO detectors, are 'broadband' detectors, and are able to follow the gravitational wave from 10 Hz to 8000 Hz. The GW150914 event was a signal from 35 Hz to 150 Hz, over a period of 0.2 seconds.

As for more detectors, they are coming online (Virgo early next year and KAGRA later), just takes time I am all for a detector in Australia... would be nice. That would primarily help with the sky localisation for EM followups.

Also, LIGO made an initial faq page which may be of interest, https://www.ligo.caltech.edu/page/faq

[Eratosthenes (Peter)]

I am astonished that the LIGO group used flimsy 40kg mirrors in the detector. This decision alone almost destroyed any chance of a successful and meaningful measurement....

These yahoos were lucky this time - thanks to the Russian researchers in Moscow who covered the LIGO group's backside...just to save on some glass costs - absolutely ridiculous.

[julianh72 (Julian)]

Originally Posted by torsion

As for the Pulsar Timing Array, that is a very interesting results. According to the models, they should have seen something and they didn't. So that says something about the models, which in turn is very interesting.

Unless I am misunderstanding the situation (which is entirely possible; probable even!), I'm not surprised that we didn't see a corresponding change in the Pulsar timing yet.

The gravitational waves reached us by travelling in a straight path 1.3 billion light years long (if "straight" means anything when we are talking about distortions of space itself!). Unless the pulsar we are monitoring happens to lie on the same "straight" path (VERY unlikely!), the path length from the Black Hole Merger to the Pulsar to Earth is longer than the "straight" path from the Black Hole Merger to Earth.

If the Pulsar happens to lie close to the straight path, between Earth and the merged Black Holes, it would have felt the gravitational waves before us, but as the cumulative path length is longer, the disruption to the regular pulsar frequency won't reach us for some time yet. If the Pulsar lies 100 light years beyond us, the gravitational waves won't reach it for another 100 years, and then it will take another 100 years for the Pulsar fluctuation signal to reach us.

[Shiraz (Ray)]

I think that the pulsar study is based on a totally different timeframe (eg cycles per year, not 100 Hz). The pulsar study is looking for long slow galaxy-class events, not small black hole or neutron star mergers - from my limited understanding, the zippy merger that was observed with LIGO would not register on the pulsar study.

For interest, it seems that Australia could possibly have had a LIGO, but the Government was not able to finance it. From Wiki, "The LIGO-Australia plan was approved by LIGO's US funding agency, the National Science Foundation, contingent on the understanding that it involved no increase in LIGO's total budget. The cost of building, operating and staffing the interferometer would have rested entirely with the Australian government.[6] After a year-long effort, the LIGO Laboratory reluctantly acknowledged that the proposed relocation of an Advanced LIGO detector to Australia was not to occur. The Australian government had committed itself to a balanced budget and this precluded any new starts in science. The deadline for a response from Australia passed on 1 October 2011." https://en.wikipedia.org/wiki/AIGO

[sjastro]

Originally Posted by julianh72

Unless I am misunderstanding the situation (which is entirely possible; probable even!), I'm not surprised that we didn't see a corresponding change in the Pulsar timing yet.

The gravitational waves reached us by travelling in a straight path 1.3 billion light years long (if "straight" means anything when we are talking about distortions of space itself!). Unless the pulsar we are monitoring happens to lie on the same "straight" path (VERY unlikely!), the path length from the Black Hole Merger to the Pulsar to Earth is longer than the "straight" path from the Black Hole Merger to Earth.

If the Pulsar happens to lie close to the straight path, between Earth and the merged Black Holes, it would have felt the gravitational waves before us, but as the cumulative path length is longer, the disruption to the regular pulsar frequency won't reach us for some time yet. If the Pulsar lies 100 light years beyond us, the gravitational waves won't reach it for another 100 years, and then it will take another 100 years for the Pulsar fluctuation signal to reach us.

To expand on Ray's post.

Gravitational waves are emitted in all directions and continuously up to the time of the Black Hole merger.

The Pulsar timing array is designed to measure fluctuations in pulsar arrival times caused by gravitational waves which alter the Earth-Pulsar distance.
The Pulsar fluctuation times are long period events, and are expected to be caused by gravitational waves of very low frequency (long period).
These very low frequency gravitational waves are generated by orbiting supermassive black hole binaries in galaxies.

GW150914 on the other hand is an example of a Black Hole merger producing gravitational waves in the high frequency range which would not impact on pulsar fluctuation time.

http://nanograv.org/assets/img/GWBigPicture.png

Regards

Steven

[silv (Annette)]

torsion:
As for the Pulsar Timing Array, that is a very interesting results. According to the models, they should have seen something and they didn't. So that says something about the models, which in turn is very interesting.

I just >>read (in the comment section) that the Pulsar Timing Array is looking for a different kind/source of GW: higher amplitudes but much much lower in frequency. Like from binary supermassive BH within 2 merging galaxies.
Ligo is not designed to detect those kind of waves and vice versa.
>>abstract

Binary supermassive black holes - that's also the subject of observation of the future eLISA in 2035, with a laser beam length of 1 million km. Well, sexy, but... that's kind of too much in the future for my attention span.
A mission for an eLisa instrument test, "Lisa Pathfinder", is going to go into science mode on March 1st.
Here, the laser beam is shortened to 38cm to fit into 1 spacecraft.
The test is about gaining info on the "rulers'" functionality and exactness in a free fall environment, which can not be obtained on Earth.
I would follow the mission or eLISA on Facebook. Only to keep being reminded of - and through that, possibly commit into long term memory what I understood so far.
But they don't have their own page. Just not sexy enough...
Ah well.

[xelasnave]

Lets build a bigger better one and rent it out?

[Eratosthenes (Peter)]

Originally Posted by xelasnave

Lets build a bigger better one and rent it out?

definitely the way to go...

but this time don't skimp on the glass in the mirrors

the clowns in the LIGO group got away with it this time, with the help of a few Russian geniuses in Moscow.

Aussie mirrors should be at least an order of magnitude heavier - at least 300kg, bare minimum anyway.

We have lots of sand on our coastline so I really dont see what the problem is...

[xelasnave]

Why have large mirrors we may need to move it.
One inspace maybe?

[torsion (Bram)]

Hi Julian,

Sorry didn't see you post, but a few have answered your point nicely.

In the Pulsar Timing Array, they use the pulsars and earth as 'the test masses' to measure the timing, while in LIGO they use the 40 kg test masses 4km apart to measure the timing.

The test masses (four of them in total per interferometer), are about 34 cm in diameter and 20 cm thick, made of low-mechanical-loss, high quality Fused Silica. They have been polished to have a concave surface on the front with a radius of about 2 km (and flat on the back). Then they are coated with high quality, low-optical-loss coatings (high reflectivity on the front and anti-reflective on the back). They are manufactured in a joined effort in the US, UK and France, with reference measurements done at CSIRO - Centre for Precision Optics (if I am not mistaken).

The concave polishing and the coatings are required to form a stable, low loss optical Fabry-Perot cavity. Any loss will remove photons which are then not used in the sensing of the signal. Also, additional loss can turn into heat, which will deform the mirrors, and introduce loss. Hence they use the low-loss materials to reduce all this.

The 40 kg is a ~4x increase in mass from the original LIGO detectors. The difficulty is homogeneous polishing and coating of the 34 cm diameter, which was quite a challenge. Any ripples etc on the mirror surface will introduce loss. Going to much larger mirrors makes the manufactory of them impossible (currently). You can think of a compound mirror (made of multiple pieces), but then any loss near the joining faces will/can increase the noise.

A nice photo of one of the Advanced LIGO mirrors is here http://www.ligo.org/multimedia/galle...d_llo_itmy.jpg. The wiggles on the mirror are from a special protective coating, which will be removed when work is done nearby. (more photos here http://www.ligo.org/multimedia/gallery/opt.php)

[Eratosthenes (Peter)]

Originally Posted by xelasnave

Why have large mirrors we may need to move it.
One inspace maybe?

At least the vacuum bit of the design is already up there....great thinking xelas

How do we get the 600kg mirrors up there though?

Do you know if there Are deposits of sand on Pluto or Europa?

May need to crunch the numbers before we float the idea on Wall Street.

The fascist bankers on Wall Street are very picky and would want some short term returns, one would think.

[xelasnave]

No mirrors just a transmitter beam splitter and receivers.

The bankers can make money short selling shares in mirror companies as sucess of the mirror less system will see them plumet.

Look I dont work on the trivial aspects of the plan I just come up with magnificent ideas it is up to the staff to iron out perceived difficulties and make my ideas work.

[Eratosthenes (Peter)]

Originally Posted by xelasnave

No mirrors just a transmitter beam splitter and receivers.

The bankers can make money short selling shares in mirror companies as sucess of the mirror less system will see them plumet.

Look I dont work on the trivial aspects of the plan I just come up with magnificent ideas it is up to the staff to iron out perceived difficulties and make my ideas work.

I dont think the good folk of iceinspace have ever doubted that Universal axiom xelas

having said that however I will say this...."it's critical that you at least help out with the nitty gritty of the Space LIGO project - especially the mirrors even if they arent really required. I am a strong believer that mirrors should be installed in the next generation of LIGO detectors irrespective of whether they are part of the measurement or not. Heavy mirrors. massive heavy mirrors - at least 15 of them weighing over 900kg each - The mirror system will impress investors and bankers to fund the project in space".

You may wish to consider consulting with an expert who is commercially savvy and understands the criminal system that underpins Wall street and the casino stock market before you stampede towards getting your little idea off the ground.