APOD: GW151226: A Second Confirmed Source ... (2016 Jun 15)

[Fred the Cat]

I'll bet today's sound will eventually make the "Top Ten"

[neufer]

I'm a little puzzled by something though. The graph seems to show the frequency a little above 32 Hertz (maybe about 40 Hz) at the beginning. The tone I hear on the other hand sounds to me closer to middle C on the piano or maybe an octave below. I seem to recall middle C being a frequency of about 256 Hertz and an octave below then being 128 Hz. Am I wrong?

The APOD clearly states: INCREASED PITCH

[neufer]

I like Betty Boop, but I don't believe she emits any gravitational waves.

One has to be an "L" shaped guy to detect them.

[ecdowney]

Is this in real-time? I mean, did these two black holes really merge in about a second?? Wow!

[Cheers]

Yes, that's what I wondered. Did it only take a second or is there something else?

[neufer]

[size=150][color=#0000FF]GW150914 merger[/color][/size]

---

Is this in real-time? I mean, did these two black holes really merge in about a second?? Wow!

Yes, that's what I wondered. Did it only take a second or is there something else?

Real time... and about 4 times longer than the GW150914 merger

[Joules]

That chirp hits a mighty high frequency for two objects that are kilometers in diameter.

[neufer]

That chirp hits a mighty high frequency for two objects that are kilometers in diameter.

Not as they near the speed of light.

[alter-ego]

That chirp hits a mighty high frequency for two objects that are kilometers in diameter.

Not as they near the speed of light.

I'm not sure what you meant; as measured, the frequency continues to increase with velocity.

[hamilton1]

The naming convention for these events is annoying; GW151226 follows the American dating format but that is confusing to Europeans who would use 261215 - these are discoveries for mankind and not just Americans.

[Markus Schwarz]

Ok. Presumably the chirp wave at the end marks the moment when the two black holes became one? Does there exist a theory / model explaining the general shape of this chirp? It would be nice to say that "this is what GR predicted the fusion of two black holes to sound like (on the GW spectrum)

I guess

This GW-emitting system is best fit by two merging black holes with initial masses of about 14 and 8 solar masses

means just that

You are correct. Within the general theory of relativity you can predict the GW spectrum emitted by two merging black holes. If you know the masses of the two black holes before merger, you can precisely predict the GW properties. The problem is that we don't know the masses of the two black holes in this case. Instead, it's used the other way around. What people do is they simulate templates of GW for given masses of the two black holes. When a GW signal is observed you basically look up in the catalogue which initial masses best reproduce the observed signal. Maybe we can get more information on the situation if we can observe the system containing the final black hole also in electromagnetic radiation.

But the abrupt ending of the signal is an indication that an event horizon has formed. It is also an indication of the no-hair-conjecture. This conjecture roughly states that black holes in general relativity don't have any "external structure". In the case of two merging black holes it means that the resulting black hole very quickly settles down to a shape without any "bumps", and which emits no further gravitational waves.

[bystander]

The naming convention for these events is annoying; GW151226 follows the American dating format but that is confusing to Europeans who would use 261215 - these are discoveries for mankind and not just Americans.

Writing dates as day month year makes as much sense as writing time as seconds minutes hours.

YYMMDD is more in keeping with international standards (see ISO 8601) than is DDMMYY.

[neufer]

That chirp hits a mighty high frequency for two objects that are kilometers in diameter.

Not as they near the speed of light.

I'm not sure what you meant; as measured, the frequency continues to increase with velocity.

A 22 solar mass binary black hole system 'touches' at a separation of ~ 22x3 = 66 km.

The 2 holes switch places on the order of every
(66 x π/2) km /(300,000 km/s) ~ 1/3,000 seconds corresponding to ~ 3,000 Hz
which should correspond to the highest possible gravitational wave frequency.

[neufer]

So... can we build an Gravitational Wave Generator and make electricity from the motion of "The Strain"? Like with an Ocean Waves... Probably not a big wave by the time it gets to us.

Since it is an action, and has an Energy, an amount, an intensity, a frequency of wavelength, and thus a Load... that means this is Gravitational Charge... The Energy Load of that action... I work with Emotional Charge...and there are other Charges as well....

We can detect distant supernova as well but we don't bother to capture their photons as an energy source; the nearby Sun is a much better source of photons. Gravitational tidal forces grow even faster as one approaches near the sources (i.e., inversely with the cube of the distance). That is why it makes much more sense to capture the energy of ocean tides due to our Moon (in conjunction with Earth's rotation & much closer than 1 light day away) rather than the feeble energy of distant black hole mergers.

[Fred the Cat]

If we could only "catch a wave" we'd be sitting on top on the world.

Surfing.jpg (12.3 KiB) Viewed 3444 times

[starsurfer]

If we could only "catch a wave" we'd be sitting on top on the world.

Surfing.jpg

starsurfer approves of this post.
Also only realised now that there is actually sound and why geckzilla said "Bwoop"!

[Craig Willford]

Probably nobody is even watching the Discussion page on this APOD of 2016 06 15 anymore, but I couldn't help myself.

With two detected in three months, one has to be simultaneously interested that they are so often (from an observer's point of view) and yet so rare (as the volume of space inside a radius of 1.4 billion light years is so huge, to only have one every three months is amazing). It is going to be so very exciting as still more detections take place. Still yet more exciting when LIGO can expand to have more detectors and we can pinpoint the spot in the sky from which it came (by triangulation).

The description talks of red shift. Spectrum shifts are detected in relation to known expected, non-shifted emission or absorption lines. Gravity waves don't have those. What red shift was detected and how?

If there was normal matter in close proximity to the black holes as they spiraled down, I would think the massive gravity waves might so compress and distend the matter that they would display absorbed energy with bright, high frequency photons that might be detected if a telescope were looking in the right direction at the right time, even at a distance of 1.4 billion light years.

Craig Willford

[Joules]

The 2 holes switch places on the order of every
(66 x π/2) km /(300,000 km/s) ~ 1/3,000 seconds corresponding to ~ 3,000 Hz
which should correspond to the highest possible gravitational wave frequency.

So we're hearing years (orbits) go by.
Doesn't seem to be much distortion of the spherical holes involved.
That'd damp signal, and if anything the amplitude increases with frequency right up to, almost, the end.

[ems57fcva]

Ok. Presumably the chirp wave at the end marks the moment when the two black holes became one? Does there exist a theory / model explaining the general shape of this chirp? It would be nice to say that "this is what GR predicted the fusion of two black holes to sound like (on the GW spectrum)

I guess

This GW-emitting system is best fit by two merging black holes with initial masses of about 14 and 8 solar masses

means just that

You are correct. Within the general theory of relativity you can predict the GW spectrum emitted by two merging black holes. If you know the masses of the two black holes before merger, you can precisely predict the GW properties. The problem is that we don't know the masses of the two black holes in this case. Instead, it's used the other way around. What people do is they simulate templates of GW for given masses of the two black holes. When a GW signal is observed you basically look up in the catalogue which initial masses best reproduce the observed signal. Maybe we can get more information on the situation if we can observe the system containing the final black hole also in electromagnetic radiation.

But the abrupt ending of the signal is an indication that an event horizon has formed. It is also an indication of the no-hair-conjecture. This conjecture roughly states that black holes in general relativity don't have any "external structure". In the case of two merging black holes it means that the resulting black hole very quickly settles down to a shape without any "bumps", and which emits no further gravitational waves.

I see no need for the no-hair conjecture here. The loss of the gravitational wave signal only means that the object has settle into hydrostatic equilibrium. So even if the merging and final objects were not black holes, they still are stars of some kind (quark stars?), and in any case will act as a liquid and quickly settle down into a stable shape. And even if these are black holes, they still have settled down into their own equivalent of hydrostatic equilibrium. (FWIW - I do not believe in black holes, but I do support the fundamentals of GR. So even if GR is not totally correct, these discoveries still are a huge validation of the fundamentals of GR; and show that any theory that improves of GR must still be build on the same foundational principles as GR was.)

[ems57fcva]

I agree with the earlier posters who did not like the use of a placeholder for this APOD. Certainly there should have been a note mentioning the news conference, but a normal picture. Then this video could have been the next day's APOD.

[alter-ego]

The description talks of red shift. Spectrum shifts are detected in relation to known expected, non-shifted emission or absorption lines. Gravity waves don't have those. What red shift was detected and how?

That's right, the redshift is not directly measured.
Instead GW strain amplitude (the measured quantity) is used to calculate the distance, which in turn using the standard cosmological model yields the redshift, z. [ Strain ≡ ΔL/L ∝ r_s/r where r_s = Schwarzschild radius, and r = luminosity distance ]

If there was normal matter in close proximity to the black holes as they spiraled down, I would think the massive gravity waves might so compress and distend the matter that they would display absorbed energy with bright, high frequency photons that might be detected if a telescope were looking in the right direction at the right time, even at a distance of 1.4 billion light years.

Assuming a mass could survive long enough during coalescence to reach unity strain (unity strain ~ Schwarzschild radius), most likely a vast amount of heat will be generated rather than a lot of high energy photons. Heat and destruction would depend on the strain amplitude and duration (i.e. total merger mass) and details of the unlucky mass. A rocky body would certainly have a lot of debris while a gas cloud would get hot and maybe not break up. Simply put, I expect the mass-to-energy conversion ratio from GW strain oscillations would be exceedingly small compared to a supernova-like event (e.g. Type Ia) which is required for visibility over 1.4 billion ly.

[starsurfer]

I agree with the earlier posters who did not like the use of a placeholder for this APOD. Certainly there should have been a note mentioning the news conference, but a normal picture. Then this video could have been the next day's APOD.

I didn't see any problem with the placeholder, it made things even more exciting!

[Chris Peterson]

I agree with the earlier posters who did not like the use of a placeholder for this APOD. Certainly there should have been a note mentioning the news conference, but a normal picture. Then this video could have been the next day's APOD.

I didn't see any problem with the placeholder, it made things even more exciting!

Maybe the first time. But not this time, when it was pretty obvious what the announcement was going to be, and it was something expected. Placeholders should be reserved only for the most stupendous news... which this was not.

It just wasted a day of APOD for much of the world.

[ems57fcva]

I agree with the earlier posters who did not like the use of a placeholder for this APOD. Certainly there should have been a note mentioning the news conference, but a normal picture. Then this video could have been the next day's APOD.

I didn't see any problem with the placeholder, it made things even more exciting!

Maybe the first time. But not this time, when it was pretty obvious what the announcement was going to be, and it was something expected. Placeholders should be reserved only for the most stupendous news... which this was not.

It just wasted a day of APOD for much of the world.

Also, that chirp video deserved to be up for a whole day, instead of less than half of a day.

I appreciated the head-up that the placeholder gave, and even watched the press conference myself. Even so, APOD is an educational/entertainment web site, not a news site. Its job is to help us all understand astronomy/astrophysics (and occasionally some closely related topics) and that includes recent breaking news about those fields. It does not need to cover the news as it happens. In fact, not doing so gives the editors more time to construct a good page on the topic (although the final page was quite good in this case).

[ems57fcva]

If there was normal matter in close proximity to the black holes as they spiraled down, I would think the massive gravity waves might so compress and distend the matter that they would display absorbed energy with bright, high frequency photons that might be detected if a telescope were looking in the right direction at the right time, even at a distance of 1.4 billion light years.

Assuming a mass could survive long enough during coalescence to reach unity strain (unity strain ~ Schwarzschild radius), most likely a vast amount of heat will be generated rather than a lot of high energy photons. Heat and destruction would depend on the strain amplitude and duration (i.e. total merger mass) and details of the unlucky mass. A rocky body would certainly have a lot of debris while a gas cloud would get hot and maybe not break up. Simply put, I expect the mass-to-energy conversion ratio from GW strain oscillations would be exceedingly small compared to a supernova-like event (e.g. Type Ia) which is required for visibility over 1.4 billion ly.

A rocky body would likely be turned molten if is was close enough, but its emissions would be quite pale compared to even the surrounding stars. The chemical binding energy that would be released just does not amount to all that much. As for a gas cloud: It would freely distort as the gravitational waves went through without being heated at all. A gas cloud cannot "hold" any strain, while a solid object can be strained and absorb energy from a changing strain.