First images of the Black hole
Black holes are among the most profound predictions of Einstein’s theory of general relativity. Originally studied as a mere mathematical consequence of the theory rather than as physically relevant objects, they soon became thought of as generic and sometimes inevitable outcomes of the gravitational collapse that initially forms a galaxy.
In fact, most physicists have suspected that our own galaxy revolves around a supermassive black hole at its centre. There are other ideas too – such as “dark matter” (an invisible substance thought to make up most of the matter in the universe). But now an international team of astronomers, including a team that I led from the University of Central Lancashire, has unveiled the first image of the object lurking at the centre of the Milky Way – and it is a supermassive black hole.
This means there is now overwhelming evidence for the black hole, dubbed Sagittarius A*. While it might seem a little scary to be so close to such a beast, it is in fact some 26,000 light-years away, which is reassuringly far. In fact, because the black hole is so far away from Earth, it appears to us to have about the same size in the sky as a donut would have on the Moon. Sagittarius A* also seems rather inactive – it is not devouring a lot of matter from its surroundings.
DID YOU KNOW?
What is relative theory?
Have you heard of scientist Albert Einstein? He was a scientist who predicted that mass can change depending on the speed of the object. Einstein came up with his first theory of relativity, called the theory of special relativity, in 1905. It revealed that no material object can ever travel as fast as light, which has a constant speed for all observers, no matter their motion. The speed of light is thus the “speed limit” of the universe.
Einstein conceived his second relativity theory, called the theory of general relativity, in 1916. This theory concerns gravity, one of the fundamental forces in the universe. Gravitation is a very weak force. For this reason, its distinctive effects are evident only on very massive objects. The theory of general relativity thus describes such large-scale physical phenomena as the movement of planets, the birth and death of stars, black holes, and the evolution of the universe.