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A mesmerizing NASA animation shows how a nearby black hole would warp spacetime like a fun-house mirror

Aria Bendix , Business Insider US
 Sep 28, 2019, 03:07 PM
A still image of a black hole, seen from the side.
NASA’s Goddard Space Flight Center/Jeremy Schnittman
  • A new NASA animation shows what you'd see if you were hanging out near a black hole.
  • The black hole's strong gravity would distort your view: From the side, the outer ring, known as the accretion disk, would appear to bend around a dark abyss. It would also be brighter on one side than the other.
  • But if you were to look at the black hole from up above, the ring would form a near-perfect circle and the light would appear more evenly distributed.
  • This creates a kind of fun-house mirror effect in which your vantage point changes your view.
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Until recently, scientists could only speculate about the appearance of a black hole.

Given that a black hole's gravitational pull is so strong that anything, including light, gets devoured, it's extremely difficult to capture one on camera. To see a black hole at all, we have to rely on light from the stars and other matter that get sucked in (before they disappear).

In April, a group of scientists from the international Event Horizon Telescope Collaboration published the world's first photograph of a black hole. The image validated our understanding of black holes as dark spheres surrounded by a glowing ring of light, but the photo looked more like a smudge than a detailed snapshot.

A new video from NASA, however, shows what the black hole might look like if researchers were able to film it in action - or if you just happened to be hanging out nearby.

In the animation, gravity twists light into a mesmerizing gyre that shifts based on your vantage point.

The visualization first shows what a black hole would look like from the side (the way it appears in the still image above): You'd see a dark sphere in the centre. That's the hole's "shadow" - where light gets bent and captured. The boundary of that shadow is known as the "event horizon" or "point of no return," since beyond that, a black hole's gravitational force is strong enough to suck anything that approaches into the abyss.

Just outside the event horizon is a thin halo known as a "photon sphere," which consists of light rays circling the black hole.

NASA's Goddard Space Flight Center/Jeremy Schnittman

The most captivating part of the visualization, however, is the outer ring of hot matter known as the "accretion disk." It's made of dead stars, planets, asteroids, comets, and other particles that are dragged in by hole's gravitational pull. (NASA scientists just caught one of these star deaths on camera.)

The path of light appears to bend around the sphere, forming a hump at the bottom and top. The disk is brighter on the left side because the glowing gas there would be moving toward you at close to the speed of light. The gas on the right side is moving away from you, so it's not as luminous. (Think of the way a beam from a lighthouse becomes insanely bright when it's pointed directly at you.)

But things change in the visualization when you look at the black hole from above. Suddenly, the bright light becomes evenly dispersed because, from that vantage point, no parts of the disk are moving toward or away from you. The disk also forms a neat circle instead of the "double hump" you'd see from the side angle. The photon sphere stays the same, though, because light is essentially trapped there in perfect orbit.

Take a look:

NASA compares this stretching, twisting, bending journey of light to a carnival mirror.

"Simulations and movies like these really help us visualize what Einstein meant when he said that gravity warps the fabric of space and time," Jeremy Schnittman, the NASA astrophysicist who created the visualization, said in a statement.

The animation also gives context to the black hole photograph released in April. In that photo, the accretion disk looked significantly brighter on the bottom of the image and darker on the top. NASA's visualization is a reminder that a view like that would change based on our location.

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