What Are Black Holes And How Do They Form?
Where Gravity Is King!
A black hole is a mysterious object in space with a mass so great, and gravitational field so strong, that nothing can escape its mighty pull; not even light! Hence, the name ‘black hole’ because they don’t emit or reflect anything so are essentially invisible! Black holes are believed to form when an object gains sufficient mass and when large stars die.
Black Holes, What Are They?!
A black hole is the name given to a mysterious type of object in space, first theorised by scientists as a consequence of Einstein’s theory of General Relativity, but later indirectly observed by astronomers.
They are objects with an enormous amount of concentrated mass and an extremely strong gravitational field. So strong that no particles, or even radiation such as light, can escape its mighty pull! This is how the name ‘black hole’ came about on account they don’t emit or reflect anything so are essentially invisible!
A certain distance from a black hole, related to its mass, is a point known as an ‘event horizon’ which is the point beyond which nothing can return. So don’t stray too close to a black hole’s event horizon otherwise you’ll never be seen again!
Are There Different Types Of Black Holes?
Yes there are! Astronomers believe there are three main types of black holes depending on their size and mass.
The largest black holes are called ‘supermassive’ black holes and are believed to reside at the centre of every galaxy. They have a mass several million times greater than our Sun with a gravitational field so strong that billions of stars and planets are kept in orbit about them. Astronomers have discovered a supermassive black hole called Sagittarius A* at the centre of the Milky Way Galaxy!
The most common type of black hole is believed to have formed from large dying stars several times bigger than our Sun but would fit within a 20 kilometre wide sphere. These are called ‘stellar’ black holes
The smallest black holes are known as 'primordial' black holes and maybe as small as a single atom but with the mass of a large mountain.
How Do Black Holes Form?
A black hole is believed to form when an object in space grows and reaches a sufficient mass to warp the very fabric of 'spacetime', so severely, that nothing can resist its pull. These black holes will continue to grow as they absorb interstellar dust and gas even particles from the ever-present cosmic background radiation!
Black holes can also form when large stars, several times larger than our Sun, begin to die as they run out of nuclear fuel. As the star dies and collapses their cores become denser and denser. This may result in a Supernova before the collapsed core forms a dense stellar black hole.
How Do Astronomers Study Black Holes?
By their very nature black holes are impossible to study directly because they are essentially invisible! So scientists can only study them indirectly by observing the effect their extremely large gravity has on nearby objects (stars) or the lensing effect they have on the light of background stars and galaxies!
Astronomers can also use space-based telescopes, such as the Chandra X-ray Observatory, to study gases and particles which black holes sometimes strip from nearby stars and accelerate to high temperatures before passing their event horizon! Never to be seen again!