Question

are black holes all black​

Answer 1

Explanation:

A black hole is a region of spacetime where gravity is so strong that nothing—no particles or even electromagnetic radiation such as light—can escape from it. ... In many ways, a black hole acts like an ideal black body, as it reflects no light.

Answer 2

You will probably find more material on the internet, but I've tried to provide a very lucid and basic explanation here (not that I'm an expert myself, but yeah, bear with me)

Consider a spherical body (let's say it's mass is 'M' and radius is 'R'). Now suppose due to some reason, the volume goes in decreasing BUT the mass remains the same.

The escape velocity √(2GM/R) from such a dense material will be very, very high. Suppose the radius is sooo small that √(2GM/R) >/= c (where, c= speed of light = 3 X 10^8)

The escape velocity for such an object is equal or greater than the speed of light!!! Uhh... if this still sounds confusing, don't worry :)

This simply means that anything starting from the object with a speed less than the speed of light will return to the object (but note here that we are neglecting the effect of any other objects in space)

Now according to the "Theory of Relativity", it is not possible to achieve a velocity greater than 'c' for any material object. Thus, NOTHING can escape from such a dense material. And such objects are known as black holes. And you know what else is interesting? EVEN LIGHT CAN'T ESCAPE from a black hole!!

Now comes, WHY can't you see a black hole?

The reason for not reflecting and not emitting is that the enormous gravity of the black hole does not let anything including light, escape from it. However, its effects can be observed. It would appear as a black sphere against background stars and the like.

"The biggest problem with trying to see a black hole is that even the supermassive ones (with masses millions of times heavier than our sun) are relatively tiny. What’s more, because of their strong gravity, black holes tend to be surrounded by other bright matter that makes it hard to see the object itself.

The biggest problem with trying to see a black hole is that even the supermassive ones (with masses millions of times heavier than our sun) are relatively tiny. What’s more, because of their strong gravity, black holes tend to be surrounded by other bright matter that makes it hard to see the object itself.That’s why when hunting for black holes, astronomers don’t usually try for direct observation. Instead, they look for evidence of the effects of a black hole’s gravity and radiation"

(Source for this paragraph: vox.com)

But any photo you’ve seen of a dark mass warping spacetime … well, that’s just an illustration xD

_____________________________________

I think I've wasted enough of your time, now let's come to YOUR question-

So how exactly does a black hole look like?

Answer: We don't know yet, duh! we only have theories, but no one knows for sure

"It might seem a bit like looking for a black cat in a coal cellar", said Stephen Hawking (if you don't know him, you must probably be living under a rock)

Now the answer to YOUR question,

Check out lecture no. 4 (The Theory of Everything by Stephen Hawking)....and yupp, BLACK HOLES AIN'T SO BLACK!

Hope it helps :)