Altered Assessment Reveals Imperfections in Groundbreaking Milky Way Black Hole Snapshot
A group of scientists from Japan's National Astronomical Observatory (NAOJ) argues that the groundbreaking image of the supermassive black hole at the heart of our galaxy, released by the Event Horizon Telescope Collaboration in May 2022, isn't entirely accurate.
The initial image of Sagittarius A* displayed a colossal black hole with a mass of four million solar masses as a menacing black cloud encircled by a radiant ring – the black hole's accretion disk. In their paper, the new team suggests that the object might have a more stretched out disk shape instead. They published their proposed black hole structure in the Monthly Notices of the Royal Astronomical Society.
The 2022 image featured the first glimpse of Sagittarius A*, the object at our galaxy's core, and was the second black hole image produced by the Event Horizon Telescope (or EHT). The EHT's first black hole image, published in 2019, depicted the black hole Messier 87 (M87).
Black holes are areas of spacetime with gravitational fields so intense that not even light can escape beyond a certain distance - known as the black hole's event horizon. Surrounding the event horizon is a glowing region of superheated matter - the accretion disk. The recent team's findings focus on the shape of Sagittarius A*'s accretion disk, which they claim is not the doughnut-like structure depicted in the 2022 image.
The EHT is a vast radio observatory consisting of a network of radio telescopes. EHT data reveal the black hole's silhouette against the backdrop of its accretion disk, since light cannot escape the event horizon.
Miyoshi Makoto, an astronomer at the NAOJ and co-author of the paper, stated in a Royal Astronomical Society release, "We suspect that the ring image resulted from errors during EHT's imaging analysis, and that part of it was an artifact, rather than the actual astronomical structure."
The team analyzed the same 2017 data that the EHT Collaboration used to create its black hole image but employed a different approach to analysis, indicating an elongated accretion disk compared to the doughnut-like structure depicted in the 2022 image.
The team's radio image of Sagittarius A*. Image: Miyoshi et al.
According to the recent team, the black hole's accretion disk is elongated rather than the ring-like structure shown in the 2022 image. The M87 black hole also appears to have a ring-like shape in the EHT image, later developed into a polarized image of the object, complete with the structure of its magnetic fields.
In August, the EHT published a new method to enhance the telescope's resolution, suggesting sharper images of black holes in the near future. Future observations using this technique could clarify the actual structure of Sagittarius A*.
Eventually, a space-based mission to enhance the sharpness of EHT images may be launched. This mission concept involves investigating black holes' photon rings, called the Event Horizon Explorer. The cost is estimated at $300 million.
Boosting our understanding of the cosmos' most extreme environments – those sustaining black holes, neutron stars, and collisions between these objects – will deliver insights into the gravitational universe and the core of our own galaxy.
The NAOJ researchers believe that future technological advancements in space-based observations, such as the Event Horizon Explorer, could provide more accurate images of black holes, potentially challenging their current findings about Sagittarius A*. The recent study suggests that the supermassive black hole at the center of our galaxy might have a more elongated accretion disk rather than the doughnut-like structure depicted in the 2022 image, which was influenced by space technology and ground-based radio telescopes like the Event Horizon Telescope.
