Supermassive black hole at centre of Milky Way seen for first time

The black hole itself, known as Sagittarius A*, cannot be seen because no light or matter can escape its gravitational grip. But its shadow is traced out by a glowing, fuzzy ring of light and matter that is swirling on the precipice at close to the speed of light.

The image was captured by the Event Horizon telescope (EHT), a network of eight radio telescopes spanning locations from Antarctica to Spain and Chile, which produced the first image of a black hole in a galaxy called Messier 87 in 2019.

The image provides compelling proof that there is a black hole at the centre of the Milky Way, which had been the working assumption of mainstream astronomy. A minority of scientists had continued to speculate about the possibility of other exotic objects, such as boson stars or clumps of dark matter.

To the untrained eye, the latest image might appear roughly similar to that of the black hole, M87*, but the two objects are extremely different, according to the EHT team.

M87*, by contrast, is one of the largest black holes in the universe and features vast, powerful jets that launch light and matter from its poles into intergalactic space.

Despite being local in astronomical terms at 26,000 light years away, observing SgrA* turned out to be more challenging than anticipated. The team spent five years analysing data acquired during fortuitously clear skies across several continents in April 2017.

The EHT picks up radiation emitted by particles within the accretion disc that are heated to billions of degrees as they orbit the black hole before plunging into the central vortex. The blotchy halo in the image shows light bent by the powerful gravity of the black hole, which is 4m times more massive than that of our sun.