An Earth-sized telescope will allow astronomers to glimpse the black hole at the centre of the Milky Way.

Scientists across the globe are currently linking up telescopes across the globe to form the Event Horizon Telescope (EHT) which will be the first instrument ever to take detailed pictures of a black hole.

Even though the Milky Way's black hole, known as Sagittarius A* (pronounced 'Sagittarius A-star'), is four million times more massive than the sun, it is tiny to the eyes of astronomers.

It is the equivalent of standing in New York and reading the date on a penny in Germany or seeing a grapefruit on the Moon for someone standing on Earth.

But if successful, it will prove for the first time that black holes have 'event horizons' – an edge from which nothing can escape, not even light.