New visualization reveals in detail the surreal craziness that extreme gravity causes to the appearance of the material around you.
By A. J. Oliveira
Sep 27, 2019, 6:42 pm – Posted on Sep 27, 2019, 6:41 pm
Black holes top the list of the most bizarre things in the universe. Like the Big Bang, they represent a frontier of science: they are the limit of the laws of physics. But a new simulation produced by NASA allows us to better understand the mind-blowing dynamics surrounding these giants.
They are true cosmic kaleidoscopes. The insane gravity of a black hole draws large amounts of gas and dust into its orbit, forming the so-called accretion disk.
This structure heated and accelerated by intense magnetic fields gives off a strong glow. Without it, it would be impossible to discern the contours of the event horizon – the point of no return from which the attraction of the black hole over an object becomes inescapable.
To understand why a black hole accretion disk looks the way it does, you need to remember Einstein's teachings.
The theory of general relativity has revealed to us that bodies with too much mass (and thus too much gravity) distort the fabric of spacetime around them.
This is not particularly intuitive, but the apparent "emptiness" of space is actually a mesh sewn by two inseparable threads: space and time. Together they form a continuum, a kind of lightly deformed tissue by planets like Earth, moderated by stars like the Sun, and extreme by black holes.
Nothing escapes this distortion, not even the light. And precisely because of this, the vicinity of a black hole looks so strange. The light emitted by different parts of the accretion disc undergoes varying deformations.
From time to time, bright spots appear in that "soup" of plasma gas because of the effects of magnetic fields. And when rotating, the points are stretched and shrunk due to differences in rotational speed. Closer to the black hole, the gas moves at practically the speed of light. Already at the edges, it gets a little slower.
This discrepancy produces lighter and darker bands. Another interesting fact is that the left side looks brighter than the right. This is because, on the left, the gas is accelerating towards us, while on the right, it moves away. The appearance of the surroundings of a black hole therefore depends greatly on the viewing angle.
When we are aligned with the disc and see its edge, it looks even more distorted. Closer to the object, gravity is so strong that it forms a “photon ring” around it. There are actually several rings that are becoming thinner and faded, made of light that has orbited one or more times before escaping toward us. The photons outline the shadow of the black hole – it measures almost twice the event horizon.
Jeremy Schnittman, an expert at NASA's Goddard Center who generated the stunning images with a computer program, sheds light on how well they illustrate something that in theory is so abstract. "Simulations and movies like these really help us see what Einstein meant when he said gravity distorts the fabric of spacetime," he said in a statement.