Astrophysicists are in a perpetual quest for answers, trying to understand the workings of the Universe, which is full of celestial objects, often enigmatic, but so extraordinary. If luminous stars have long monopolized researchers and astronomy enthusiasts, today they are far from being the only ones to occupy the minds of the curious. Black holes are probably the most fascinating objects in the cosmos, both for their strangeness and for their devastating capabilities.


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Black hole, cosmic monsters:
But how can such a cosmic phenomenon occur? Scientists believe that some black holes, known as primordial, appeared shortly after the Big Bang in the early universe. Supermassive black holes have been discovered in some galaxies, allowing us to consider that they were created at the same time as their host galaxy.
Another category of black holes could be the result of the death of a massive star, when it collapses on itself, causing a supernova. If a black hole occupies zero space, it has a very large mass. This mass represents the major part of the mass that was once that of a star. Of course, as gluttons, black holes become more and more massive as they gobble up the surrounding matter. The zone of no return, i.e. the event horizon, gradually grows with the black hole.
The existence of black holes in the Universe can lead to another reflection. If they absorb everything in their path, can they represent a real danger? But first of all, are there many of them? Or are they quite rare anomalies?

One question is certainly on your mind. If black holes are invisible, can we still describe them? The answer is yes!
On the one hand, scientists have been able to study them thanks to the techniques previously described, but on the other hand, an image made the rounds in 2019. The international team of the Event Horizon Telescope has unveiled, after two years of data processing and more than ten years of work, the first ever photo of a black hole. It is the picture, made with very long baseline interferometry, of the supermassive black hole M87, nestled in the heart of the galaxy M87, located 55 million light years from Earth. We can discover a black disk surrounded by a ring of light, corresponding to the shadow of this colossal object. Its mass is equivalent to 6.5 billion solar masses and the diameter of its event horizon is estimated at 254 astronomical units, that is 254 times the distance to the Earth and the Sun!
But let's take a closer look at this strange object in order to reveal its structure. A black hole is composed of an external event horizon, a second internal event horizon, and its singularity.
The event horizon marks the limit around the mouth of the black hole. As soon as a particle enters this horizon line, it is trapped and doomed to disappear. Gravity is constant in this zone, whatever the distance. However, it happens that matter, attracted by the black hole, ricochets on the event horizon. It is then projected outwards, accompanied by a shower of light jets of matter.
The singularity represents the inner region of the black hole. This is where the overwhelming mass of the object remains. The singularity is completely hidden and corresponds to the unique point where the mass of the black hole is concentrated in spacetime.





On the program today:
00:00 Introduction
02:25 Crossing our solar system
10:42 What is a black hole?
11:25 How do we know black holes exist?
13:29 What does a black hole look like?
15:56 How do black holes form?
17:37 How many black holes are there in the Universe?
20:20 The closest black hole to the Earth
23:05 A rogue black hole
25:12 Cygnus X1
27:25 A tilted black hole
32:29 The smallest black holes
36:02 Sagittarius A*
39:18 A bulletshooting black hole
41:46 The rarest black hole in a neighboring galaxy
45:29 Henize 210
47:46 The fastest spinning black hole
51:57 A cannibal black hole
55:15 Medium weight black holes
58:04 A collision between two black holes?
01:00:12 The brightest black hole
01:03:03 The oldest known black hole
01:06:10 The biggest black holes
01:09:22 GNz7q, the "Missing Link
01:12:45 What happens at the center of a black hole?
01:14:12 What if we went in?