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What is a black hole

I have not heard such incompetent explanations as ones implemented when some tries to explain what a black hole is (as in an astronomical object).

A black hole has NOTHING to do with a hole. The terminology is not a clue for symbology.

A black hole is a spherical astronomical object (in simple terms, a ball of stuff floating in space). As a sphere of mass, it can behave similar to stars, such as the one in our solar system (the Sun).

Things which are the same for a black hole compared to a star such as the Sun:

Both are spherical astronomical bodies

Both can have a system of stars or planets orbiting around them

Stars or planets can orbit the object in a stable orbit, or plunge towards the center of the system in a spiral towards collision.

Things which are different for a black hole compared to a star such as the Sun:

A black hole does not emit light like a star does

A black hole cannot emit light like a star

A black hole can be much, much larger (and heavier) than a star. Black holes millions of times the weight of our Sun exist.

The "black" part comes from the black hole's extremely large mass. The larger an object is, the larger its gravitational pull becomes. Your weight on Earth is almost entirely due to the mass of the Earth. A rocket attempting to escape from the pull of Earth's gravity must spend a lot of fuel (energy) in order to not only lift itself from the surface of the planet, but to also give itself enough velocity (speed) in order to not fall back on the surface.

You will be much heavier on the surface of a large object such as Jupiter, Saturn, or the Sun. We will ignore the fact that large astronomical bodies are not made from rock, but are made from gases. A rocket starting from the surface of a larger astronomical body (planet or star) would need to use many times more fuel in order to enter into orbit and escape falling back on the surface.

Light moves very fast. Its speed in vacuum is 300,000 kilometers per second. For those who failed to adopt SI a long time ago, that equates to 671,000,000 mph. However, a black hole is so massive that this tiny "rocket" of a particle of light is not even fast enough to escape the black hole's gravitational pull.

A black hole is therefore a black star, or a black sphere. Against a dark background, it is invisible since it does not emit light. Against a white background (of a galaxy or a star), a black hole would appear as a black disc. Astronomers most often find a black hole indirectly. They can detect star systems orbiting objects of which indicate an extremely gravitationally powerful object at the center. They can also detect a black hole from the telltale signs of stars falling on spiral orbits towards destruction. Black holes can also be observed as they swallow a star, or if they pass in front of a source of background light.

As far as peacefully falling into a black hole, as you frequently hear people talk about, then forget about it. The gravitational pull is so strong that, for example, if you were to approach a black hole feet first, the small distance difference between your feet and your head means that more force will be applied to your feet. With the huge mass of the black hole, the difference in pull is so strong, it will rip your body or a spaceship apart.

If it were up to me to be the first to name these objects, I would have called them a "black star" instead.

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