A group of Japanese scientists with the Event Horizon Telescope team have conducted a new study of the center of our Galaxy and the Sagittarius A* black hole there. They’ve imaged a surprisingly elongated structure.
New observation of the Sagittarius A* object
A research team led by Associate Professor Makoto Miyoshi of the National Astronomical Observatory of Japan (NAOJ) has independently re-analyzed data from observations of a supermassive black hole at the center of the Milky Way Galaxy obtained and published by the international Event Horizon Telescope Project. They found that the structure is slightly extracted in an east-west direction.
This study, published in Monthly Notices of The Royal Astronomical Society, takes a fresh look at the publicly available data from the Event Horizon Telescope and demonstrates a scientific process in which confidence in the answer increases as different researchers continue to study and debate the theory.
The Milky Way galaxy in which we live contains more than 100 billion stars like the Sun. There are countless such large galaxies in the Universe, most of which are believed to have supermassive black holes at their centers with masses millions and billions of times the mass of the Sun. Our star system also has a supermassive black hole at its center called Sagittarius A*.
A black hole absorbs everything, including light, making it impossible to see the most supermassive black hole, but analysis of the stars orbiting around the black hole at high speed indicates that Sagittarius A* has a mass that is about 4 million times that of the Sun. Carefully observing its surroundings can give us clues about the nature of the invisible black hole.
Results of the Event Horizon Telescope observations
Event Horizon Telescope observed Sagittarius A* in 2017 with eight ground-based radio telescopes, using a technique known as radio interferometry to combine results from different telescopes. The results of these observations were published in 2022, including an image of a bright ring structure around the central dark region, indicating the presence of a black hole.
Unlike ordinary photos, observational data linking several distant radio telescopes contains many gaps in completeness, therefore special algorithms are used to create an image from these data. In this study, the team applied commonly used traditional methods to the Event Horizon Telescope data, in contrast to the original method by which it had been processed before.
Miyoshi explains, “Our image is slightly elongated in the east-west direction, and the eastern half is brighter than the western half. We think this appearance means the accretion disk surrounding the black hole is rotating.”
The EHT’s observational data and analysis methods are freely available, and many researchers have confirmed the analysis of the team that collected them. This study is also part of the regular verification activities.
Various methods of data analysis
Radio interferometry, connecting telescopes around the world, is an advancing technology, and research on data analysis and image processing continues, including knowledge of statistics and other related disciplines.
The structures presented in this study differ from the results of the EHT team, but both are valid structures derived from the data using appropriate methods. The EHT plays an important role in black hole research by requiring independent verification and providing open data for its implementation.
Scientists hope that a more reliable picture of Sagittarius A* will emerge from the researchers’ active discussion based on improved analysis methods and further observations from 2018.
Provided by phys.org