Keio University
A research team consisting of Kazuki Yanagisawa, MS ’26, from the Keio University Graduate School of Science and Technology and Professor Tomoharu Oka of the Faculty of Science and Technology, together with researchers from the National Astronomical Observatory of Japan (NAOJ), analyzed radio intensity data from Sagittarius A* (Sgr A*), the compact radio source at the center of the Milky Way Galaxy, obtained with the Atacama Large Millimeter/submillimeter Array (ALMA).
Using observational data acquired on August 31, 2016, the team identified brightness variability structures with characteristic timescales of approximately 30 minutes and 50 minutes. These variations may be produced by two hot spots orbiting the supermassive black hole of four million solar masses while gradually losing energy.
This study suggests that the brightness variability observed in Sgr A* may be caused by the formation, evolution, and disappearance of multiple hot spots. Whereas periodic and random variations in Sgr A* have traditionally been thought to originate from different physical mechanisms, the team’s latest findings provide new observational evidence that both types of variability may be explained by a unified hot-spot model, and offer an important clue toward understanding the physical environment in the immediate vicinity of a black hole. The team’s findings were published in the May 18 issue of The Astrophysical Journal Letters, an American academic journal that specializes in astrophysics research.
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