APOD: Simulation: Two Black Holes Merge (2019 Apr 14)

[APOD Robot]

Simulation: Two Black Holes Merge

Explanation: Sit back and watch two black holes merge. Inspired by the first direct detection of gravitational waves in 2015, this simulation video plays in slow motion but would take about one third of a second if run in real time. Set on a cosmic stage the black holes are posed in front of stars, gas, and dust. Their extreme gravity lenses the light from behind them into Einstein rings as they spiral closer and finally merge into one. The otherwise invisible gravitational waves generated as the massive objects rapidly coalesce cause the visible image to ripple and slosh both inside and outside the Einstein rings even after the black holes have merged. Dubbed GW150914, the gravitational waves detected by LIGO are consistent with the merger of 36 and 31 solar mass black holes at a distance of 1.3 billion light-years. The final, single black hole has 63 times the mass of the Sun, with the remaining 3 solar masses converted into energy in gravitational waves. Since then the LIGO and VIRGO gravitational wave observatories have reported several more detections of merging massive systems, while last week the Event Horizon Telescope reported the first horizon-scale image of a black hole.

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[Boomer12k]

Bit anti-climatic... but interesting.I guess it is to be expected that all the energy inside, would stay inside... thus, basically "BLOP" together...

:---[===] *

[De58te]

That's cool. Sort of looks like stirring a thick broth of soup. Minus the stirring spoon. But that is what it looks like when the observing point of the Earth is directly above the spinning disk of the black holes. What would it look like if we the observers would see it edge on, like we would see the black holes at the centre of the Milky Way?

[orin stepanek]

That's cool. Sort of looks like stirring a thick broth of soup. Minus the stirring spoon. But that is what it looks like when the observing point of the Earth is directly above the spinning disk of the black holes. What would it look like if we the observers would see it edge on, like we would see the black holes at the centre of the Milky Way?

Would a Black hole look like a disk? Or more like a ball? I may be all wet; but I think the Black hole would be more like a ball!

[neufer]

In a previous discussion I wrote:

The black hole's shadow has EVERYTHING to do with gravitational lensing of the hot accretion disk behind the black hole.

• It is closely related to the larger Einstein rings of
  more distant [and TOTALLY un-gravity-induced reddened] radiation sources.

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Credit: Nicolle R. Fuller/NSF

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The path of light around a black hole gets severely distorted by gravity. In this diagram, the Earth is off to the right, and light form material behind the black hole gets bent toward us, leaving a [somewhat larger] “hole/shadow” where the black hole itself is.

In today's APOD we get to see both the two dark black hole shadows of radius: R_bhs ~ 2.6 r_s
: (where r_s = Schwarzschild radius).

as well as the larger counter rotating Einstein ring of radius: R_er ~ sqrt(2r_sD_o)
: (where D_o = the distance of the observer above the scene).

Since R_er ~ 3 R_bhs at the video's end one can estimate that this event is being observed
from the nearby distance D_o ~ 30 r_s : (where r_s = Schwarzschild radius of the merged hole).

(Hence, this is a nearby spaceship's view of a merger rather than
what one might observe from the distant Earth where R_er >> R_bhs .)

[Chris Peterson]

Bit anti-climatic... but interesting.I guess it is to be expected that all the energy inside, would stay inside... thus, basically "BLOP" together...

It may not be visible in an image like this, but most certainly all that energy does not stay inside. Quite the opposite, several solar masses of energy is released in the form of gravitational waves... more radiated power at the moment of the merger than the combined output of every star in the observable universe.

[Chris Peterson]

That's cool. Sort of looks like stirring a thick broth of soup. Minus the stirring spoon. But that is what it looks like when the observing point of the Earth is directly above the spinning disk of the black holes. What would it look like if we the observers would see it edge on, like we would see the black holes at the centre of the Milky Way?

Would a Black hole look like a disk? Or more like a ball? I may be all wet; but I think the Black hole would be more like a ball! :shock:

A black hole is a point (or very close to it). That is surrounded by a spherical event horizon (although in the case of binary black holes, those spheres become distorted). But how it "looks" is much more complex, given that spacetime is so distorted around them. We are basically observing this through a complex optical system that changes the apparent (but not actual) shape of things- often in very non-intuitive ways.

[orin stepanek]

That's cool. Sort of looks like stirring a thick broth of soup. Minus the stirring spoon. But that is what it looks like when the observing point of the Earth is directly above the spinning disk of the black holes. What would it look like if we the observers would see it edge on, like we would see the black holes at the centre of the Milky Way?

Would a Black hole look like a disk? Or more like a ball? I may be all wet; but I think the Black hole would be more like a ball!

A black hole is a point (or very close to it). That is surrounded by a spherical event horizon (although in the case of binary black holes, those spheres become distorted). But how it "looks" is much more complex, given that spacetime is so distorted around them. We are basically observing this through a complex optical system that changes the apparent (but not actual) shape of things- often in very non-intuitive ways.

So I Get a '?' I come out with wow; that flew a bit over my head! In other words when 2 black holes come together; they distort each other like you wouldn't believe before they merge? Then do they (does it) become spherical again? Maybe that just flew over my head a little bit? Thanks!

[Chris Peterson]

Would a Black hole look like a disk? Or more like a ball? I may be all wet; but I think the Black hole would be more like a ball! :shock:

A black hole is a point (or very close to it). That is surrounded by a spherical event horizon (although in the case of binary black holes, those spheres become distorted). But how it "looks" is much more complex, given that spacetime is so distorted around them. We are basically observing this through a complex optical system that changes the apparent (but not actual) shape of things- often in very non-intuitive ways.

So I Get a '?' I come out with wow; that flew a bit over my head! In other words when 2 black holes come together; they distort each other like you wouldn't believe before they merge? Then do they (does it) become spherical again? :shock: Maybe that just flew over my head a little bit? Thanks!

Certainly the event horizons of binary black holes become significantly non-spherical as they approach merger.

[neufer]

Would a Black hole look like a disk? Or more like a ball? I may be all wet; but I think the Black hole would be more like a ball!

A black hole is a point (or very close to it). That is surrounded by a spherical event horizon...

<<A black hole is a region of spacetime exhibiting such strong gravitational effects that nothing—not even particles and electromagnetic radiation such as light—can escape from inside it.

At the center of a black hole, as described by general relativity, lies a gravitational singularity, a region where the spacetime curvature becomes infinite. For a non-rotating black hole, this region takes the shape of a single point and for a rotating black hole [i.e., any realistic black hole], it is smeared out to form a ring singularity that lies in the plane of rotation. In both cases, the singular region has zero volume. It can also be shown that the singular region contains all the mass of the black hole solution. The singular region can thus be thought of as having infinite density.>>

[bls0326]

Above is taken from one of the links in APOD's Black Hole Shadow post a couple of days ago. It tries to show how light/space in quadrants around the black hole are distorted and would appear to an observer. In a larger image one can see some light that is not only bent but makes an orbit or two around the black hole before getting away thus making some bands of color near the black hole.

PS The image is based on a Kerr Black Hole. There are some some other Black Hole options in the ESA ACT Visualization.
https://www.esa.int/gsp/ACT/phy/Project ... WebGL.html

[neufer]

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Above is taken from one of the links in APOD's Black Hole Shadow post a couple of days ago. It tries to show how light/space in quadrants around the black hole are distorted and would appear to an observer. In a larger image one can see some light that is not only bent but makes an orbit or two around the black hole before getting away thus making some bands of color near the black hole.

PS The image is based on a Kerr Black Hole. There are some some other Black Hole options in the ESA ACT Visualization.
https://www.esa.int/gsp/ACT/phy/Project ... WebGL.html

The image above is based on a Kerr Black Hole whose angular momentum vector is pointing up.

• Presumably, the simulation in today's APOD represents Kerr Black Holes
  whose angular momentum vectors are pointing towards us.

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The supermassive black hole at the core of supergiant elliptical galaxy Messier 87, with a mass ~7 billion times the Sun's, as depicted in the first image released by the Event Horizon Telescope (10 April 2019). Visible are the crescent-shaped emission ring and central shadow, which are gravitationally magnified views of the black hole's photon ring and the photon capture zone of its event horizon.

The crescent shape arises from the [Kerr] black hole's rotation and relativistic beaming;
the shadow is about 2.6 times the diameter of the event horizon.>>

[tomatoherd]

I don't appreciate it in the simulation. but wouldn't the rotation speed up as the distance between lessens?

[neufer]

wouldn't the rotation speed up as the distance between lessens?

Yes... but it might be hard to follow at an accelerated RPM
(and it might adversely affect certain susceptible viewers).

[Hopalong]

" ... the gravitational waves ... are consistent with the merger of 36 and 31 solar mass black holes at a distance of 1.3 billion light-years. The final, single black hole has 63 times the mass of the Sun, with the remaining 3 solar masses converted into energy in gravitational waves."
The two black holes have 36 and 31 solar masses, i.e. 67 solar masses in total. The resulting single black hole has 63 solar mass - so the difference is 4 solar masses. However, the text refers to "the remaining 3 solar masses". Am I missing something?