Independent analysis confirms first black hole image
The Event Horizon Telescope (EHT) collaboration wowed the world in 2019 with the first picture ever taken of a black hole’s shadow. Now, an independent group has reanalysed the EHT data, and its results, published on 11 November in Nature, largely corroborate the original findings.
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 2022, 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.
The new independent analysis was carried out by S. Lai, N. Thyagarajan, O. I. Wong, and F. Diakogiannis of the Commonwealth Scientific and Industrial Research Organisation. The researchers used an algorithm to combine telescope measurements of a black hole in a different way to the original analysis. Their results, published on 11 November in Nature, include new images of the black hole and output the same, ring-like shape as the original 2019 image.
The Nature article references the original research by Lai, Thyagarajan, Wong and Diakogiannis, published in Nature with the doi: (2026). It also references the earlier questioning by Miyoshi, M., Kato, Y. & Makino, J., published in the Astrophysical Journal 933, 36 (2022).
The EHT collaboration’s original image was produced by stitching together data from an array of ground-based radio telescopes across several continents. The new analysis used a different algorithm to combine the same telescope measurements, addressing concerns that the circular shape seen in the original image could have been an artefact of the team’s image-reconstruction techniques.
Some researchers were unconvinced by the original 2019 image, arguing that the circular shape seen in that shot was an artefact of the team’s image-reconstruction techniques. The new results largely corroborate the original findings, with the fresh analysis outputting the same, ring-like shape.
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