The Event Horizon Telescope (EHT) collaboration wowed the world in 2019 with the first picture ever taken of a black hole’s shadow. Some researchers were unconvinced, arguing that the circular shape seen in that shot was an artefact of the team’s image-reconstruction techniques. Now, an independent group has reanalysed the EHT data, and its results, published on 11 November in Nature — including new images of the black hole — largely corroborate the original findings¹.

To image black holes, the international EHT collaboration stitches together data it collects simultaneously from an array of ground-based radio telescopes that stretches across several continents. The reconstruction is extremely challenging, but in principle the result is an image with the same level of detail, or resolution, that would be achieved with a single radio dish as wide as Earth.

Although blurry, the EHT shot of a supermassive black hole at the centre of the M87 galaxy was consistent with astrophysical models based on Albert Einstein’s general theory of relativity, which first predicted the existence of black holes. The image had a bright ring of roughly the correct radius, given what was known about the size of the black hole, with a darker disk at the centre.

However, starting in 2022², Junichiro Makino, an astrophysicist at Kobe University in Japan, and his collaborators began questioning those conclusions. By applying one of the data-analysis techniques the EHT collaboration had used, but with slightly different assumptions, Makino’s team obtained a different result. Their image shows a glob of radio emissions rather than a ring.