What would it be like to look into a black hole?

Black Hole :

A black hole is a place in space where gravity pulls so much that even light can not get out. The gravity is so strong because matter has been squeezed into a tiny space. This can happen when a star is dying. Because no light can get out, people can't see black holes. They are invisible



As for the black hole itself, you wouldn't be able to see it directly, as it's enshrouded in gas and dust.


In principle there is no limit to the size of a black hole: it can be as light as a feather or as heavy as a few billion Suns! Their size varies accordingly.

 A black hole with a mass equal to that of the Sun would have a radius of three kilometres. Furthermore the radius of a black hole scales in proportion to its mass. So a typical stellar-mass black hole (ten times the mass of the Sun) would have a radius of thirty kilometres, and a supermassive black hole (e.g., one million solar masses) would have a radius of three million kilometres. 

Black holes of different masses have the same basic properties (they all have no hair). They are expected to display different behaviours only because the typical lengths and timescales involved are proportional to the mass and because black holes of different sizes exist in different environments. In the next section we quickly review the different weight classes.

The world of black holes is full of surprises: there may be black holes smaller than a flea and lighter than a feather and tiny black holes could one day be produced in the laboratory. Primordial black holes may have existed during the early stages of the Universe, a few moments after the Big Bang. 

At that time the temperature and pressure were so gigantic that they could have squeezed matter down to a singularity: however only primordial black holes of about a billion tons could have survived until the present day; the lighter ones would all have evaporated. The lightest black holes are called elementary black holes, as they would be like elementary particles. With the startup of the Large Hadron Collider (LHC) these microscopic black holes received a lot of attention as they might be produced during particle collisions at the LHC. However, they would immediately disintegrate again, and would therefore not have time to accrete matter and cause any macroscopic effects.



The traditional recipe to make a black hole needs a single ingredient: a very massive star at the end of its life. More recently another mechanism has been found, the collision and merger of very dense objects, such as neutron stars. Black holes that form through these mechanisms usually have masses three to ten times greater than the Sun and they are called stellar-mass black holes. In theory black holes of any size can exist. Supermassive black holes of a million to a billion times the mass of our Sun are found at the centre of (almost) all massive galaxies. How they form is still not fully understood.