Black holes are perhaps the most enigmatic objects in the Universe.
• A black hole harbours a singularity at its centre, where all known physical laws break down. This singularity is clothed by an event horizon – an imaginary surface that prevents anything, including light, from escaping it.
Albert Einstein’s general theory of relativity admits the existence of such objects, and Karl Schwarzchild first discovered this possibility in 1915.
- However, even Einstein didn’t believe that such objects could exist in the natural world.
- Even when theoretical evidence suggested that black holes could be formed by the gravitational collapse of massive stars, many leading physicists did not agree.
- Arthur Eddington expected that “there should be a law of nature to prevent the star from behaving in this absurd way.”
Although during the first half of the 20th century black holes were restricted to the domain of mathematical studies, recent astronomical observations suggest that the universe is littered with black holes.
Astronomers believe that our own galaxy hosts a supermassive black hole at its centre (which is a few million times more massive than the Sun) – apart from 100 million “small” black holes, each several times more massive than the Sun. And our galaxy is just one among 100 billion galaxies in the observable universe!