enter image description here

I was expecting a whirlpool in 3D and the matter glowing from friction as it nears the center, as I expected a event horizon to be negligible visually.

How does this depiction work? How big is the central sphere? I am puzzled by the perpendicular circles. Are they the event horizons if they are both visible? What would be a path of a particle as it gets swallowed into the singularity?


4 Answers 4


First note that this is a fictional movie and the image is an artist's impression, not a detailed simulation. The public seems to think the movie is some sort of fictionalized documentary, which it never claimed to be. That said, the image is qualitatively conveying some of what happens near a black hole.

The diagonal disk is the accretion disk -- this is where matter is spiraling inward due to gravity, friction, and electromagnetic forces too. It glows because it is very hot.

The circular ring is the result of gravity bending the light emitted from the far side of the accretion disk into our line of sight. A similar effect happens when the light source is much farther behind the black hole, as seen in this Wikimedia image:

black hole image

As for event horizons, no, you would only see the outer one by definition. (An event horizon is nothing more or less than a surface which delineates which regions of spacetime can communicate with each other.) Since the image in question is made for primarily artistic purposes, I wouldn't try to read too much into details that you see.

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    $\begingroup$ Well, from what I can read in places like here: wired.com/2014/10/astrophysics-interstellar-black-hole (and in the video), they not only claim to be accurate, but they claim that they may have even advanced our knowledge of black holes from the simulations carried out for the movie. The movie itself was originally conceived by Kip Thorne and Lynda Obst to try to depict Kip's theoretical work in a movie, all the fiction and plot came later from Nolan. $\endgroup$
    – guillefix
    Nov 24, 2014 at 12:54
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    $\begingroup$ My instinctive reaction as someone who simulates black hole accretion is to be rather skeptical about the scientific novelty. Ray tracing has been done before; it's not that hard to trace geodesics even in Kerr spacetime. The real action is simulating the dynamics of the disk and the formation of a jet. $\endgroup$
    – user10851
    Nov 24, 2014 at 13:04
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    $\begingroup$ I remember reading somewhere that Chris Nolan decided to cut out Doppler effects, and he also had them drop the angular momentum well below what would be required for the extreme time dilation the crew experiences. He apparently thought that these would confuse the audience too much. $\endgroup$
    – Jold
    Nov 24, 2014 at 14:04
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    $\begingroup$ @jld - Yes, as noted by Jean-Pierre Luminet in two comments here, they did leave out the Doppler effect, and Kip Thorne says in Ch. 8 of The Science of Interstellar that for visualization purposes they chose a rotation rate of 60% of maximum rather than the 1 part in 100 trillion below the maximum assumed for time dilation calculations (the higher spin rate would result in an asymmetrical flattening of one side of the black "shadow", and "some peculiar features of the star streaming and the accretion disk"). $\endgroup$
    – Hypnosifl
    Nov 24, 2014 at 15:41
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    $\begingroup$ I have to disapprove of starting your answer off with saying that this is not a detailed simulation, given that one of the main selling points of the movie is that they actually did run a detailed (I'm not sayin complete) simulation, especially by Hollywood standards. They may have taken some artistic liberties with the results of that simulation, but probably not to such a degree that the usefulness of the simulation itself is entirely lost. $\endgroup$
    – David Z
    Nov 24, 2014 at 17:53

The bright parts around the black hole are the accretion disk, which is in reality just a flat disk in the equatorial plane similar to the rings of Saturn, but is distorted visually by gravitational lensing. You can see a page here that gives some code for creating images using ray-tracing of light rays in curved spacetime, which offers a more schematic diagram of the visual appearance of a disk around a black hole (with a checkerboard pattern on it for clarity):

enter image description here

In this Q&A with Kip Thorne, he gives some background on how they created the images, indicating that they used a more sophisticated technique than ray-tracing:

I had been seen many years ago an image of an accretion disk with gravitational lensing that Jean-Pierre Luminet in France had made. I had sort of forgotten about it, but when I first saw the gravitationally lensed accretion disk that you actually see in the movie, it was a mixture of amazement on one hand and recognition that “Yes I do remember seeing something like that, years ago.” And a bit of awe and excitement that this team at Double Negative had just taken the equations I had given them — they don’t just use ray tracing, they propagate ray bundles or light beams — they’d used light beam propagation equations, laid down their own accretion disk based on artistic models based on astrophysicist’s stuff, and come back to me with a full-blown image of the sort you see in the movie. I was really impressed and gratified that they pulled it off and was so pleased with how it looked.

They didn't simulate all the optical effects that would be seen though--the physicist mentioned above, Jean-Pierre Luminet, comments in a facebook post here that the Interstellar image doesn't include "the strong Doppler and gravitational spectral shifts induced by the rotation of the disk at relativistic speed", and that after commenting about this he got a message from Kip Thorne saying that "The doppler shift was left out of the images, because (as you showed long ago) it makes the disk highly asymmetric, and much harder for a mass audience to grasp." Thorne also comments on this in the above Q&A:

I discuss [all of the compromises] that I’m aware of in the book. One example is in the accretion disk around “Gargantua,” the black hole, where if you put in the Doppler shift, one side of the disk is moving towards you and the other side away, that changes the colors from blue on one side to red on the other, that’s probably ok, fine, but it changes the brightness so that one side is far brighter and the other is far dimmer than the other, and by the time you’ve done that, a general audience is going to be totally baffled by what they’re looking at. So a conscious decision was made to leave out the Doppler shift and have an accretion disk that has the right shape but not the right lopsidedness.

Luminet also links to his original 1979 paper on the visual appearance of a black hole with a thin accretion disk, and also gives this image "computed by J.A.Marck in the 1990's" which does take into account the Doppler shift, as you can see it's a bit less cinematic:

enter image description here

Luminet also has a blog where he wrote a series of posts about Interstellar, including this one where he discussed his work on the visual appearance of a black hole (the other posts in the series can be found by working one's way back from the sixth installment).

I also found this video linked to and explained in this reddit post, showing a schematic image of what it would look like to fly by a black hole with an accretion disk at relativistic speeds. The color scheme is artificial, different colors represent different light intensities.

Edited to add: A paper describing the physics and computer modeling behind Interstellar's black hole, co-authored by Kip Thorne, has just been put up on arxiv.org here:

Gravitational Lensing by Spinning Black Holes in Astrophysics, and in the Movie Interstellar

And there's also this one on the wormhole, if anyone's interested.

  • $\begingroup$ It might be a bit more cinematic today with higher resolution and modern rendering (which has come a long way since the 1990s), even notwithstanding the asymmetry from the Doppler shift. $\endgroup$ Aug 30, 2015 at 12:54
  • $\begingroup$ Not very cinematic? That picture looks freakin' awesome -- I'd love to see that done again with a full-on modern sim. $\endgroup$ Feb 1, 2017 at 10:08

This is explained thoroughly in Thorne's book "The Science of Interstellar". There were two scientific papers based on the simulations: One in physics and one in computer rendering.

The two circles are caused by gravitational lensing by a very rapidly spinning black hole. The radius of this black hole is 150 million kilometers with a mass of 100 million Suns.

  • $\begingroup$ Are you sure about those numbers? 150 million kilometres is about the radius of the Earth's orbit so, to my uninformed eye, 100 Suns seems like a very low mass for such a large object, especially as one naively thinks of black holes as being exceptionally dense. $\endgroup$ Nov 24, 2014 at 15:36
  • 1
    $\begingroup$ It is 100 million suns and Kip Thorne admits that realistically it should be on the order of 200 million suns but 100 million is the quoted number since it is sort of a nice sounding whole number. $\endgroup$
    – K7PEH
    Nov 24, 2014 at 15:40
  • $\begingroup$ Have they published those papers already? $\endgroup$ Nov 25, 2014 at 7:05
  • 1
    $\begingroup$ Sorry, fixed that: It is indeed a 100 million Suns. $\endgroup$ Nov 25, 2014 at 14:24

The horizontal circle is probably the accretion disc of the black hole.

The vertical circle might depict the effect of gravitational lensing (although I am not sure this depiction is accurate).

  • 1
    $\begingroup$ "...is probably the..." If you were not sure, why did you even answer? This should probably have been a comment. $\endgroup$
    – user74560
    Jan 5, 2017 at 3:08
  • $\begingroup$ This answer was formulated shortly after I joined the network. It may be that my reputation at that time was not yet sufficient to comment. $\endgroup$
    – M.Herzkamp
    Jan 10, 2017 at 14:39

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