A new image of a supermassive black hole has revealed more of the disc of matter falling into it and the powerful winds created by that process. The black hole in question – M87* – was the first black hole to be directly imaged a few years ago. This new data will help researchers complete the picture.
M87* is about 55 million light years away, and it lies at the centre of an enormous galaxy called M87. In 2017, the eight telescopes of the Event Horizon Telescope (EHT) took the first image of M87*, a fuzzy-looking doughnut shape showing the silhouette of the black hole against a background of glowing matter falling into it in what is called an accretion flow.
Now, another team of researchers has employed a network of 10 radio telescopes to take another image, using a longer wavelength of radio emissions. They spotted a similar doughnut shape, but it was about 50 per cent thicker than the one seen by the EHT.
“Frankly speaking, I did not expect to see the ring with these observations, while we expected we might see the outer part of the accretion flow,” says Keiichi Asada at Academia Sinica in Taiwan. Because the observing frequency of this set of telescopes is about one-third of that of the EHT, the image should be about three times blurrier, which the researchers expected to smear out the black hole’s shadow in the centre.
Instead, the image showed the black hole’s silhouette, the accretion flow and the jet emerging from the system. Simulations of the system showed two surprises: the jet’s base is wider than anticipated on the basis of previous models of black hole jets, and the accretion flow seems to be powering an unexpectedly strong wind.
Those two phenomena may be related, but it will take more observations and simulations to be sure. How exactly matter behaves close to a black hole, including how these extraordinary jets are launched, has been a major question in astrophysics for decades.
“We only had EHT before in order to probe the very vicinity of the black hole… Now, we obtained another tool,” says Asada. “By combining information obtained at different frequencies, we will be able to understand the accretion flow and innermost region of the jet together with the black hole itself.” There are already plans to observe M87* at an even broader range of frequencies, which should allow researchers to put together a “multi-coloured” image of the black hole and its strange environs.