ESO to announce "unprecedented discovery" on October 16

[Tullius]

1 hour ago, UmbralRaptor said:

Also, it's really cool how fast LIGO has gone from "we can detect gravitational waves" to constraining stellar astrophysics.

Yes, that is probably the most fascinating thing of this whole endeavour.

51 minutes ago, Green Baron said:

I doubt that was the case. I would guess that's within the margins of signal detection and processing in the instruments.

The time difference is certainly correct, as otherwise we would lose a large amount of value of the parallel observation of the event. As an example, VIRGO detected the gravitational waves 22 milliseconds before LIGO Livingston, and 3 milliseconds later it was also picked up by LIGO Hanford, so we know exactly when it happened. Also the gamma-ray burst was observed by two space telescopes (Fermi and INTEGRAL). And knowing the exact timing of 1.7 seconds between the gravitational waves and the gamma-ray burst is a valuable in its own right.

As to why, I found an article from the links on wikipedia:

Quote

The neutron star merger presents some puzzles of its own. For example, the gamma rays were relatively faint, even though the burst was closer than any previously measured short burst by a factor of 10, McEnery notes. That could be because researchers saw the merger from a funny angle, she says. A gamma ray burst is thought to emerge when jets of hot matter moving at near–light-speed shoot out along the rotational axis of the newborn black hole, beaming radiation into space like a lighthouse. In this case, observers on Earth may not be looking right down the jet but may be viewing it from a slight angle, McEnery says—astronomers’ first off-axis view of an astrophysical jet.

The long lag before astronomers began to pick up radio and x-ray emissions supports that picture, says Raffaella Margutti, an astrophysicist at Northwestern University in Evanston, Illinois, who studied the event with NASA's orbiting Chandra X-ray Observatory. The radio and x-ray signals come from the jet, which at first would have beamed them too narrowly along its axis to be seen from Earth. As the jet slowed, however, radiation would emerge at wider angles, making the signals detectable off-axis.

(Source: http://www.sciencemag.org/news/2017/10/merging-neutron-stars-generate-gravitational-waves-and-celestial-light-show)

That may be part of the explanation. Another might (just guessing) be that the 100 seconds of gravitational wave observation might detail the seconds right before the explosion, while the gamma-rays etc. are the result of the explosion.

 

The whole thing is just something that is mind-bogglingly huge:

• 10,000 Earth masses of gold and platinum are expected to have formed!
• The paper detailing the astronomical observations is said to have 4600 authors, about one third of all astronomers!

And now, place your bets: What has formed out of this collision? A neutron star heavier than any known neutron star, or a black hole lighter than any known black hole?

Edited October 16, 2017 by Tullius

[PakledHostage]

2 hours ago, Tullius said:

And now, place your bets: What has formed out of this collision? A neutron star heavier than any known neutron star, or a black hole lighter than any known black hole?

What about a quark star? Now that would be a thing!

[cubinator]

4 hours ago, Shpaget said:

So, why did the gravitational wave come to Earth 2 seconds before the X-rays?

I think the X-rays actually started being emitted a little after the big gravitational disturbance.

It'll be really cool to see what more we can learn about these collisions from their gravitational waves!

[insert_name]

3 hours ago, Tullius said:

Yes, that is probably the most fascinating thing of this whole endeavour.

The time difference is certainly correct, as otherwise we would lose a large amount of value of the parallel observation of the event. As an example, VIRGO detected the gravitational waves 22 milliseconds before LIGO Livingston, and 3 milliseconds later it was also picked up by LIGO Hanford, so we know exactly when it happened. Also the gamma-ray burst was observed by two space telescopes (Fermi and INTEGRAL). And knowing the exact timing of 1.7 seconds between the gravitational waves and the gamma-ray burst is a valuable in its own right.

As to why, I found an article from the links on wikipedia:

That may be part of the explanation. Another might (just guessing) be that the 100 seconds of gravitational wave observation might detail the seconds right before the explosion, while the gamma-rays etc. are the result of the explosion.

 

The whole thing is just something that is mind-bogglingly huge:

• 10,000 Earth masses of gold and platinum are expected to have formed!
• The paper detailing the astronomical observations is said to have 4600 authors, about one third of all astronomers!

And now, place your bets: What has formed out of this collision? A neutron star heavier than any known neutron star, or a black hole lighter than any known black hole?

How do they define astronomers in that context

[YNM]

This is great. Back then they all talked about GRBs without having any real idea what the hell they are. In the same time, they haven't detected any gravitational waves from supposedly-GRB-producing event.

And suddenly, the paths cross.

So, congratulations everyone. And thank you the Universe.

Shame on ESO though as I believe it involved waaay more than themselves !

Edited October 17, 2017 by YNM

[PB666]

5 hours ago, cubinator said:

I think the X-rays actually started being emitted a little after the big gravitational disturbance.

It'll be really cool to see what more we can learn about these collisions from their gravitational waves!

Gravitational waves are created before the two neutron stars collide. As they approach the two objects circle each other with higher and higher omega. This increases the tone of the energy pulse carried on space-time. Since space-time is massless the pulse travels at the speed of light, just like all massless waveforms. The tone increases and the two neutron stars collide. Neutron stars are the remnant of supernova, such stars create clouds of gas that surround them at distances too far from the star to coalesce at the systems center, however as two neutron stars pass close they draft debris from the outer regions other Neutron stars system. Neutron stars also have very intense magnetic fields. Neutron stars are typically 10 km in diameter and as they approach they are multiples of this distance apart, the gravitational waves in space-time we are measuring are from a distance of 100,000,000 of light years. a light year is 10E13 km. IOW the intensity of the perceived acceleration in 10E40 times stronger between the two worlds relative to what we can detect. The closer they get the faster things close by get pulsed. Now imagine your little KSP craft entering the atmosphere from say 1700 m/s versus 4000 m/s, that brighter glow is cause be collisions of particles being acceleration E = hv, higher energy collisions result in brighter light. Electrons are being stripped from their atoms from increasingly energetic shells and when the recombine they create more energetic light. Prior to us detecting the gravitational waves the approaching stars are causing low energy radiation from less energetic collisions. As they get closer the orbiting stars cause some of this radiation to be blue shifted (toward us) and red shift(away from us). As they get really close the shift increases more. Consequently the higher energy pre-GRB hv observed is expected prior to the formal collision.

Conceptionally however I should make the point that when two stars cross each others systems boundaries, a collision of sorts has already happened, there is already material colliding and producing radiation. If you imagine relative interstellar speeds in the 10k m/s to 100k m/s range you are looking at a fairly bright glow of relatively low intensity. Such collisions will produce plasma and can be subject to the accelerations of the magnetic field. The problem is that unless your are already looking at that system, you probably will never set your instruments in a mode to detect the radiation emitted. Its only because we can see the pulsing gravitational waves that we see things are going to happen. If you then take a close look, of course you will see something. GRB are a known commodity they were detecting using nuclear bomb surveylance satellites. However, we don't often see hv emitted before GRB until more or less recently. More sensitive gravitatonal wave detection will give better spectrographic information of the entire process of a merger, not just the last few seconds.

I should also correct one media fallacy. It is generally accepted that light is not the only massless field that travels at C. In this regard the discovery is non-exceptional. What is more valuable is the finding that the energies and material present are suitable for heavier than iron element formation. The increasing frequency of light and finally x-rays and gamma suggests that these mergers not only have sufficient energy but a means of blowing material away from the merging stars. This is important because many neutron star mergers will create black holes from which no matter escapes. When two black holes merge only the lightest elements in the surrounding gases escape due to x-ray pressure.

 

[PB666]

9 hours ago, Tullius said:

Yes, that is probably the most fascinating thing of this whole endeavour.

The time difference is certainly correct, as otherwise we would lose a large amount of value of the parallel observation of the event. As an example, VIRGO detected the gravitational waves 22 milliseconds before LIGO Livingston, and 3 milliseconds later it was also picked up by LIGO Hanford, so we know exactly when it happened. Also the gamma-ray burst was observed by two space telescopes (Fermi and INTEGRAL). And knowing the exact timing of 1.7 seconds between the gravitational waves and the gamma-ray burst is a valuable in its own right.

As to why, I found an article from the links on wikipedia:

That may be part of the explanation. Another might (just guessing) be that the 100 seconds of gravitational wave observation might detail the seconds right before the explosion, while the gamma-rays etc. are the result of the explosion.

 

The whole thing is just something that is mind-bogglingly huge:

• 10,000 Earth masses of gold and platinum are expected to have formed!
• The paper detailing the astronomical observations is said to have 4600 authors, about one third of all astronomers!

And now, place your bets: What has formed out of this collision? A neutron star heavier than any known neutron star, or a black hole lighter than any known black hole?

If the neutron star that forms is heavier then it simply forms a black hole, a small one that would generally go unnoted.  Note that two merging neutron stars of 10km diameter will only produce a result of 12.6km in diameter, two small for even the most sensitive telescopes to see. You can see the effects of neutron stars because of the intense magnetic fields that spin around them, these can be noisy or quiet. Thus a nuetron star can disappear and appear to be a black hole. Black holes are may not be visible but when they absorb matter they release UV and Xrays and cause a glow of excited plasma at their 'poles'.

Once you have a merger, there is a certain inevitability that it will form a black hole. The problem is that such a small black hole would begin to disintegrate unless more material is added over time due to hawkings radiation, which converts a higher percentage of mass the smaller the black hole is. 

[YNM]

17 hours ago, insert_name said:

How do they define astronomers in that context

Anyone with access to the equipments ?

[PakledHostage]

Derek at Veritassium made a good summary of this observation:

 

[sevenperforce]

On 10/17/2017 at 12:34 AM, PB666 said:

Once you have a merger, there is a certain inevitability that it will form a black hole. The problem is that such a small black hole would begin to disintegrate unless more material is added over time due to hawkings radiation, which converts a higher percentage of mass the smaller the black hole is. 

Define small. Neutron stars are typically 1-3 solar masses, so we're looking at 2-6 total solar masses of matter. If that collapses into a black hole, it would have to eject 99.999998% of its mass or more in the collision, or the black hole remnant would still be too large to undergo net shrinkage from Hawking radiation.

A black hole smaller than the mass of our Moon will lose mass over time; a black hole larger will gain mass, even if the only things falling onto are photons from the cosmic microwave background. 

[Diche Bach]

On 10/17/2017 at 12:21 AM, PB666 said:

Gravitational waves are created before the two neutron stars collide. As they approach the two objects circle each other with higher and higher omega. This increases the tone of the energy pulse carried on space-time. Since space-time is massless the pulse travels at the speed of light, just like all massless waveforms. The tone increases and the two neutron stars collide. Neutron stars are the remnant of supernova, such stars create clouds of gas that surround them at distances too far from the star to coalesce at the systems center, however as two neutron stars pass close they draft debris from the outer regions other Neutron stars system. Neutron stars also have very intense magnetic fields. Neutron stars are typically 10 km in diameter and as they approach they are multiples of this distance apart, the gravitational waves in space-time we are measuring are from a distance of 100,000,000 of light years. a light year is 10E13 km. IOW the intensity of the perceived acceleration in 10E40 times stronger between the two worlds relative to what we can detect. The closer they get the faster things close by get pulsed. Now imagine your little KSP craft entering the atmosphere from say 1700 m/s versus 4000 m/s, that brighter glow is cause be collisions of particles being acceleration E = hv, higher energy collisions result in brighter light. Electrons are being stripped from their atoms from increasingly energetic shells and when the recombine they create more energetic light. Prior to us detecting the gravitational waves the approaching stars are causing low energy radiation from less energetic collisions. As they get closer the orbiting stars cause some of this radiation to be blue shifted (toward us) and red shift(away from us). As they get really close the shift increases more. Consequently the higher energy pre-GRB hv observed is expected prior to the formal collision.

Conceptionally however I should make the point that when two stars cross each others systems boundaries, a collision of sorts has already happened, there is already material colliding and producing radiation. If you imagine relative interstellar speeds in the 10k m/s to 100k m/s range you are looking at a fairly bright glow of relatively low intensity. Such collisions will produce plasma and can be subject to the accelerations of the magnetic field. The problem is that unless your are already looking at that system, you probably will never set your instruments in a mode to detect the radiation emitted. Its only because we can see the pulsing gravitational waves that we see things are going to happen. If you then take a close look, of course you will see something. GRB are a known commodity they were detecting using nuclear bomb surveylance satellites. However, we don't often see hv emitted before GRB until more or less recently. More sensitive gravitatonal wave detection will give better spectrographic information of the entire process of a merger, not just the last few seconds.

I should also correct one media fallacy. It is generally accepted that light is not the only massless field that travels at C. In this regard the discovery is non-exceptional. What is more valuable is the finding that the energies and material present are suitable for heavier than iron element formation. The increasing frequency of light and finally x-rays and gamma suggests that these mergers not only have sufficient energy but a means of blowing material away from the merging stars. This is important because many neutron star mergers will create black holes from which no matter escapes. When two black holes merge only the lightest elements in the surrounding gases escape due to x-ray pressure.

 

It must be a truly fascinating time to be an undergraduate in physics with a thirst to push the envelope. I'm definitely too old for that sort of shenanigans . . . but you blew my mind with just the first few sentences which I put in bold.

Might try to stomach that Veritasium video to get a digestible synthesis of it but . . . to put my central question to test: "Gravitational waves" isn't simply confirming that such a thing exists a gigantic "discovery?"

What implications does this have for the whole dark matter/dark energy "we don't really understand 95% of the Universe" paradox?

[sevenperforce]

4 minutes ago, Diche Bach said:

What implications does this have for the whole dark matter/dark energy "we don't really understand 95% of the Universe" paradox?

None.

[Diche Bach]

8 minutes ago, sevenperforce said:

None.

I thought the hypothetical phenomenon known as dark matter and dark energy had a lot to do with so-called gravity though?

[sevenperforce]

10 minutes ago, Diche Bach said:

I thought the hypothetical phenomenon known as dark matter and dark energy had a lot to do with so-called gravity though?

Dark matter isn't really hypothetical, dark energy is slightly hypothetical but not really, and gravity isn't so-called. But in any case this merger of neutron stars didn't involve dark matter or dark energy or their interactions with gravity.

[Diche Bach]

3 minutes ago, sevenperforce said:

Dark matter isn't really hypothetical, dark energy is slightly hypothetical but not really, and gravity isn't so-called. But in any case this merger of neutron stars didn't involve dark matter or dark energy or their interactions with gravity.

So what is dark matter "made of?" Where does it fit on the periodic table? We have yet to measure or observe it directly right? It is merely inferred based on discrepancies between expected and observed galactic configurations, right?

I am most definitely no expert, but seems to me dark matter is still fairly hypothetical. Clearly there IS SOMETHING that accounts for the observations and the discrepancies which led to the invocation of the concept of "dark matter." But no one has yet to observe the stuff, no one knows for real what it is and it might be many things not merely one thing, eh?

This merger involved gravity and confirmation of what appears to me to be a new if not revolutionary model of what gravity is, and the paradox of dark matter and dark energy all revolve around discrepancies in observed and expected behavior where gravity is a central parameter, so I still not convinced of "zero implications."

Edited October 19, 2017 by Diche Bach
elaboration of comment/question

[sevenperforce]

2 minutes ago, Diche Bach said:

So what is dark matter "made of?" We have yet to measure or observe it directly right? It is merely inferred based on discrepancies between expected and observed galactic configurations, right?

I am most definitely no expert, but seems to me dark matter is still fairly hypothetical. Clearly there IS SOMETHING that accounts for the observations and the discrepancies which led to the invocation of the concept of "dark matter." But no one has yet to observe the stuff, no one knows for real what it is and it might be many things not merely one thing, eh?

Dark matter is directly observable and measurable; we just haven't been able to isolate it or figure out what it's made of. Most likely it is made of small particles which interact only through the weak nuclear force rather than through electromagnetic forces. 

[Diche Bach]

4 minutes ago, sevenperforce said:

Dark matter is directly observable and measurable; we just haven't been able to isolate it or figure out what it's made of. Most likely it is made of small particles which interact only through the weak nuclear force rather than through electromagnetic forces. 

Directly observable how? What kind of telescope can "see" dark matter? I think you are using a different concept of "direct measurement" than I am.

The fact it is called "dark" is indicative of the fact it is not directly observable is what I understood. It is a hypothetical force, whose presence is inferred based on the discrepancy of how galaxies SHOULD behave if the only matter present were that which IS observable (the glowing stuff) and how galaxies actually behave. Specifically, if the glowing stuff was all there was, galaxies should fly apart, so there must be other stuff we cannot see.

I know about the lensing observations, but that too strikes me as "indirect" measurement of dark matter. The stuff itself still has not been seen, merely inferred with some precision based on the effects which "it" had on observable phenonenon.

ADDIT: and I presume based on your screen name/title you are actually trained in physics (which I am NOT! ) so  . . . please be patient with me. I'm not just trying to derail the thread or be a pain in the butt or otherwise disrupt discourse. I'm honestly just curious and want to learn more.

Edited October 19, 2017 by Diche Bach
clarification

[Green Baron]

41 minutes ago, Diche Bach said:

Directly observable how? What kind of telescope can "see" dark matter? I think you are using a different concept of "direct measurement" than I am.

 

Hi !

Observable by the movement of stars, starclusters, galaxies and galaxy clusters. They do not move as indicated by the visible matter alone but like they would if there was ~5 times more matter. It is until now not visibly through telescopes, so it has been called "dark", without any intended mystification.

Dark matter doesn't interact except by gravity. But what can't be seen electromagnetically may nevertheless exist, sotosay :-)

Hope that wasn't totally wrong :-)

Edit: same with gravitational waves. They exist and can be measured, though we can't see them. They are a new sense for observing the universe, somebody said that besides seeing (telescopes) we can now hear as well.

Edited October 19, 2017 by Green Baron

[Diche Bach]

6 minutes ago, Green Baron said:

Hi !

Observable by the movement of stars, starclusters, galaxies and galaxy clusters. They do not move as indicated by the visible matter alone but like they would if there was ~5 times more matter. It is until now not visibly through telescopes, so it has been called "dark", without any intended mystification.

Dark matter doesn't interact except by gravity. But what can't be seen electromagnetically may nevertheless exist, sotosay :-)

Hope that wasn't totally wrong :-)

 

That fits with what I understood. I don't call that "direct observation." We can see the effects of something that must be there but we cannot see "it." Thus we observe dark matter, indirectly, which means, we really have no idea what it is. Merely that something is producing discrepancies in observed and expected observations.

ADDIT: anyway, Dark matter and Dark Energy are (it seems to me) quintessentially about this thing we call gravity!

Thus, it seemed to me that (a) the discovery of gravity waves; and (b) confirmation of that discovery by a different natural event might well have some implications for those theoretical constructs, with gravity being the central nexus of all three.

Edited October 19, 2017 by Diche Bach
Clarification

[sevenperforce]

48 minutes ago, Diche Bach said:

ADDIT: and I presume based on your screen name/title you are actually trained in physics (which I am NOT! ) so  . . . please be patient with me. I'm not just trying to derail the thread or be a pain in the butt or otherwise disrupt discourse. I'm honestly just curious and want to learn more.

No worries!  

48 minutes ago, Diche Bach said:

Directly observable how? What kind of telescope can "see" dark matter? I think you are using a different concept of "direct measurement" than I am.

The fact it is called "dark" is indicative of the fact it is not directly observable is what I understood. It is a hypothetical force, whose presence is inferred based on the discrepancy of how galaxies SHOULD behave if the only matter present were that which IS observable (the glowing stuff) and how galaxies actually behave. Specifically, if the glowing stuff was all there was, galaxies should fly apart, so there must be other stuff we cannot see.

I know about the lensing observations, but that too strikes me as "indirect" measurement of dark matter. The stuff itself still has not been seen, merely inferred with some precision based on the effects which "it" had on observable phenonenon.

You and @Green Baron are correct that dark matter was originally only "inferred" based on galactic rotation rates and so forth. This is definitely an "indirect" observation.

However, gravitational lensing allows something much more like direct observation. Technically, you're observing the shadow of the dark matter, just like we can detect exoplanets by measuring the periodic dip in light when they pass in front of their star. However, a shadow can be quite precise, and gravitational lensing can tell us exactly how much dark matter there is, where it is, and how it is distributed. We cannot see the dark matter itself, because it doesn't interact with light, but we can see its silhouette, which honestly is pretty much all we're looking at with most exoplanets. 

The indirect/direct thing is the same difference as saying "I only felt the guy punch me" and "I couldn't see the guy's face, but I saw his silhouette before I felt him punch me."

Edited October 19, 2017 by sevenperforce

[Green Baron]

A physicist would probably object because it is there and can be mapped for example. We can't see a lot of things because our instruments or techniques don't allow, yet they are there.

Now we could ask: Is the interaction via gravity enough for a direct observation ?

 

Edit: already outdated with @sevenperforce's last ninja stab :-)

Edited October 19, 2017 by Green Baron

[sevenperforce]

Another way of putting it...

We indirectly observe exoplanets when we detect the tug of their gravity on their parent star. We directly observe exoplanets when our telescopes see how they block light from their parent star.

We indirectly observe dark matter when we measure the anomalous rotation curves of galaxies. We directly observe dark matter when our telescopes see how it bends light from more distant galaxies.

[PakledHostage]

43 minutes ago, Diche Bach said:

That fits with what I understood. I don't call that "direct observation." We can see the effects of something that must be there but we cannot see "it." Thus we observe dark matter, indirectly, which means, we really have no idea what it is. Merely that something is producing discrepancies in observed and expected observations.

I am out of my depth on this topic, but I thought gravitational lensing around distant galaxies was one method that we can "see" dark matter, in so far as we see its effect on light bending around those distant galaxies to form Einstein rings? I understood that the amount of lensing we observe is consistent with what we expect if dark matter is indeed present?

Edited October 19, 2017 by PakledHostage

[sevenperforce]

1 hour ago, PakledHostage said:

I am out of my depth on this topic, but I thought gravitational lensing around distant galaxies was one method that we can "see" dark matter, in so far as we see its effect on light bending around those distant galaxies to form Einstein rings? I understood that the amount of lensing we observe is consistent with what we expect if dark matter is indeed present?

That ring is actually a single galaxy image, repeated several different times in several warped arcs. By using a computer to "unwarp" and resolve the images, we can find out the shape of the gravitational disturbance that warped them and thus determine the distribution of all mass within that ring. 

The resultant mass distribution might look something like this:

In this case, the lensing object would be a large galaxy cluster. The spikes would be each individual galaxy, while the big smooth lump (noticeably asymmetric) is the dark matter which pulled the galaxies together.

Depending on the clarity of the images available, you can sometimes even construct a three-dimensional image of the dark matter distribution:

It's very odd-looking, isn't it? Like, clumpy. Dark matter particles don't interact electromagnetically, so they have virtually no way to shed angular momentum, so dark matter clumps don't form into nice spheres.

Of course, good lensing depends on the existence of a resolvable light source directly behind the lensing object. If the light source is something more "blurry" like a quasar, we may only be able to get a rough determination of where the dark matter is located. However, this can still be very helpful. Consider the following:

In this rather spectacular image, the contour map shows the general density of dark matter projected onto two dimensions, as shown by lensing. You'll see that there are two large distributions of dark matter. Between them are bright images, which are the superimposed x-ray photographs from baryonic matter. 

What happened here? Well, two very large galaxy clusters collided, billions of years ago. The dust, starstuff, and other baryonic matter in the two galaxy clusters slowed as the two clusters met, heating up considerably in the process (the smaller, denser one formed that lovely bowshock on the right). Meanwhile, the two large distributions of dark matter, which don't interact at all, continued on their merry way without even noticing the collision. Because the baryonic matter slowed down, the dark matter in each cluster "outran" the cluster, which is why we see this dramatic separation. 

This video shows the animation of what happened:

 

Edited October 19, 2017 by sevenperforce

[LordFerret]

On 10/16/2017 at 2:55 PM, Tullius said:

10,000 Earth masses of gold and platinum are expected to have formed!

Trying to imagine what that would do to the market. lol

Someday, we're going to be rich.