Astronomers using an observatory on Maunakea have determined that the supermassive black hole at the center of our galaxy is, more or less, about as massive as they had previously thought.
In 2020, astronomers identified an object in the heart of the Milky Way designated Sagittarius A* estimated to have a mass about 4.3 million times that of the sun. However, that identification was unable to conclusively confirm all that mass truly belonged to a single object instead of a larger clump of matter.
But, using the Gemini telescope on Maunakea, astronomers have now confirmed that Sagittarius A* is pretty much that massive, give or take 0.1%.
The discovery is twofold, said Stefan Gillessen, the primary investigator, in a statement.
“We would like to understand whether there is anything else hidden at the center of the Milky Way, and whether general relativity is indeed the correct theory of gravity in this extreme laboratory,” Gillessen said.
Using spectroscopic data gathered by Gemini Observatory, Gillessen’s team was able to determine that the orbits of four stars near Sagittarius A* behaved in a manner that supported Albert Einstein’s general theory of relativity, which predicted that objects orbiting near a supermassive object will be different from those in normal circumstances.
By observing those four stars’ movements, astronomers were then able to use minute variations in their orbits to determine the distribution of mass within Sagittarius A*, confirming that it is a single object.
Gillessen said in his statement that the four stars tracked are so faint as to be nearly undetectable with current instruments, adding that planned telescopes such as the Thirty Meter Telescope will be necessary to make further observations.
“We will improve our sensitivity even further in future, allowing us to track even fainter objects,” Gillessen said. “We hope to detect more than we see now, giving us a unique and unambiguous way to measure the rotation of the black hole.”