A team of researchers from Japan’s National Astronomical Observatory (NAOJ) says the strange picture of the supermassive black hole at the center of our galaxy is inaccurate.
The first image of Sagittarius A* was created from data taken by the Event Horizon Telescope Collaboration, which revealed the image to the public in May 2022. It showed the black hole at the center of our galaxy as a dark black cloud surrounded by a ring of light— the hole’s accretion disk. In their paper, the latter team suggests that the object may have an elongated disk. The team published their proposed black hole structure in the Monthly Notices of the Royal Astronomical Society.
A 2022 image of the black hole shows a four million solar mass behemoth called Sagittarius A*. The first image of the central object of our galaxy and the second Event Horizon Telescope (or EHT) image of a black hole. The first EHT black hole image—the first ever—shows the black hole Messier 87 (M87), and was published in 2019.
Black holes are regions of space-time with gravitational fields so strong that even light cannot escape them at a certain distance. That distance is the event horizon of a black hole. There is a field of very hot matter around the event horizon: the accretion disk. The team’s latest paper focuses on the solid disk of Sagittarius A*, which they say has a different shape than previously thought.
EHT is the largest radio viewing site created by the radio television network. The EHT data reveal a black hole—an object that is invisible in nature, because light does not escape from the event horizon—with its silhouette behind its accretion disk.
“We think that the ring image was caused by errors during the EHT analysis and that part of it was an artefact, rather than a real astronomical structure,” said Miyoshi Makoto, an astronomer at NAOJ and an author of the paper. Proceedings of the Royal Astronomical Society.
In their study, the team analyzed the same 2017 data from which the EHT Collaboration built its black hole image. But the team used a different method of analysis than the collaboration, which shows a longer accretion disk compared to the donut structure seen in the 2022 image.
The latter team argues that the black hole accretion disk is long. In other words, it has a different structure than the ring-like disk depicted in 2022. The M87 black hole also appears to have a ring-like shape in the EHT image, the latest team to develop a split image of the object, complete with the structure of its magnetic fields.
In August, the EHT published a new method by which they improved the telescope’s resolution, pointing to sharper images of black holes in the near future. If they are to follow through, future observations could clarify the true composition of Sagittarius A*.
Even further down the road, a space-based goal to improve the sharpness of EHT images may be implemented. The concept behind the mission is the $300 million photon probe for black holes—it’s called the Event Horizon Explorer.
Improving our understanding of the most dangerous regions of the cosmos—the places that fuel black holes, neutron stars, and the collisions between the two—will reveal information about the gravitational field, and the core of our galaxy.
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