A trio of Japanese astronomers has challenged the accuracy of the first-ever image showing the supermassive black hole that lies at the heart of our galaxy.
If confirmed, the findings of the researchers from the National Astronomical Observatory of Japan (NAOJ), published in the Monthly Notices of the Royal Astronomical Society, would indicate that the image may not be a true reflection of the black hole's appearance.
The original image was released in 2022 by an international team known as the Event Horizon Telescope Collaboration (EHTC), which involves hundreds of scientists from around the world. It was created based on observations conducted in 2017 by a network of eight ground-based radio telescopes.
The EHTC image of Sagittarius A*—the black hole at the center of the Milky Way—shows a dark, central region (the black hole's shadow) surrounded by a bright ring of light (called the accretion disk) that is the result of superheated gas being accelerated by extreme gravitational forces.
It should be noted that the image has been validated by many researchers. But the latest paper, led by Makoto Miyoshi with the NAOJ, paints a slightly different picture of what the black hole, located about 26,000 light-years away, may look like.
In the latest study, which is based on a reanalysis of the EHTC data, Miyoshi and his colleagues argue that part of the black hole's appearance in the original image may actually be an artifact resulting from the process of its creation.
"Our image is slightly elongated in the east-west direction, and the eastern half is brighter than the western half," Miyoshi said in a Royal Astronomical Society press release. "We hypothesize 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."
Newsweek contacted members of the EHTC, who said that their team is formulating a collective response to the findings of Miyoshi and colleagues.
For now, Event Horizon Telescope Director Huib Jan van Langevelde directed Newsweek to a previous response addressing previous findings by the same trio of Japanese researchers that called into question another EHTC image.
In this case, the image in question was the first showing a black hole. Released in 2019, the groundbreaking image depicts the supermassive black hole at the center of the galaxy M87—known as M87*. It lies about 55 million light-years away and is one of the largest known black holes.
Like the Sagittarius A* image, the EHTC image of M87* shows a bright ring of light (the accretion disk) surrounding a dark central region (the black hole's shadow).
In a 2022 study, Miyoshi and his colleagues published a study reporting an independent image reconstruction of the M87 black hole using public EHTC data. Their reanalysis of the data that produced the original image called into question whether the ring-like structure really existed and also pointed to the possible presence of a large-scale "jet" structure.
"Our result is different from the image published by the EHTC," the researchers said in the study.
But the EHTC subsequently published a response to this study in 2022. At the time, the team said that it "welcomes critical, independent analysis and interpretation of our published results." It then noted how further research had supported the results of its original image of the M87 black hole.
"Four independent analyses have reconstructed the ring-like structure of M87, employing a diverse set of techniques," the EHTC said in the response.
It continued: "These efforts complement the three imaging and two modeling techniques in the 2019 EHTC papers presenting the first M87 results. Furthermore, the EHTC and its members have published two additional papers, employing newly developed and independent techniques, that confirm the original results."
The response went on: "Our team has determined that a new re-analysis [the 2022 Miyoshi et al. paper] is based on a flawed understanding of EHTC data and its methods, leading to erroneous conclusions. Ring-like structures are unambiguously recovered under a broad range of imaging assumptions, including field of view. Additionally, large-scale jet structures are unconstrained by this high-resolution data."
What Are Black Holes?
Black holes are regions of space-time where gravity is so extreme that nothing, not even light, can escape. Most of the time, black holes form as the remnants of stars that died in cataclysmic cosmic explosions known as supernovae.
At the center of a black hole lies the singularity—a point where gravity is predicted to be infinite and the laws of physics as we know them break down.
Surrounding this is a region known as the event horizon—the boundary beyond which nothing can escape because of the extreme gravitational pull. The event horizon is named as such because it is impossible to observe any event taking place inside it.
Supermassive black holes can have masses ranging from millions to billions of solar masses. Scientists believe that most large galaxies have supermassive black holes like Sagittarius A* at their centers.
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References
Miyoshi, M., Kato, Y., & Makino, J. (2024). An Independent Hybrid Imaging of Sgr A* from the Data in EHT 2017 Observations. Monthly Notices of the Royal Astronomical Society. https://doi.org/10.1093/mnras/stae1158
Event Horizon Telescope Collaboration (2022). First Sagittarius A* Event Horizon Telescope Results. I. The Shadow of the Supermassive Black Hole in the Center of the Milky Way. The Astrophysical Journal Letters, 930(2), L12. https://doi.org/10.3847/2041-8213/ac6674
Miyoshi, M., Kato, Y., & Makino, J. (2022). The Jet and Resolved Features of the Central Supermassive Black Hole of M87 Observed with the Event Horizon Telescope (EHT). The Astrophysical Journal, 933(1), 36. https://doi.org/10.3847/1538-4357/ac6ddb
Event Horizon Telescope Collaboration (2019). First M87 Event Horizon Telescope Results. IV. Imaging the Central Supermassive Black Hole. The Astrophysical Journal Letters, 875(1), L4. https://doi.org/10.3847/2041-8213/ab0e85
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