A black hole is perhaps one of the strangest objects in our universe. It is in fact the remains of a massive dead star that has run out of fuel and collapsed.

In our previous article “What is a Black Hole?” we looked at what a black hole was & how it was formed. Here we ask the rather obvious question :

So if we can’t see a black hole, how do we know they exist?

In short – By their gravitational effects. Though they’re not visible, we can detect or hypothesise about their presence by studying surrounding objects.

Astronomers can see material swirling around one or being pulled off a nearby visible star. The mass of a black hole can be estimated by observing the motion of nearby visible stars.

 For Example

The core, or nucleus, of Galaxy NGC 4261, is about the same size as our solar system, but it has a mass 1.2 billion times as much as our Sun’s. Such a huge mass for such a small disk indicates the presence of a black hole. The core of this galaxy contains a black hole with huge spiral disks feeding dust and other material into it.

 What happens inside a black hole?

Much is unknown. When astrophysicists talk about the workings of black holes, they speak a different language: event horizons, singularities, gravity lenses, and ergospheres – strange stuff! And yet, incredibly, Albert Einstein predicted the existence of black holes way back in 1915 in his General Theory of Relativity.