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Research confirms enormous mass of supermassive black hole at center of galaxy

A new study reveals the most precise information yet about the mass of the enormous black hole at the center of our galaxy. Like most galaxies, the Milky Way has a supermassive black hole at its heart, and the recent research shows more about the mass of this monster called Sagittarius A*or Sgr A* for short.

Illustration of the black hole Sagittarius A* at the center of the Milky Way.
Illustration of the black hole Sagittarius A* at the center of the Milky Way. International Gemini Observatory/NOIRLab/NSF/AURA/J. da Silva/(Spaceengine) Acknowledgement: M. Zamani (NSF's NOIRLab)

The researchers used instruments including the European Southern Observatory’s Very Large Telescope to measure the movements of stars near to the black hole to see how much of the mass at the center of the galaxy is due to stars, smaller black holes, and other matter, and how much is due to the black hole itself.

“With the 2020 Nobel prize in physics awarded for the confirmation that Sgr A* is indeed a black hole, we now want to go further. 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,” explained Stefan Gillessen, one of the astronomers involved in this work, in a statement. “The most straightforward way to answer that question is to closely follow the orbits of stars passing close to Sgr A*.”

The researchers found that the large majority of this mass, around 99.9% of it, was due to the black hole. We can now be confident that Sagittarius A*’s mass is around 4.3 million times the mass of the sun.

In this illustration, stars are seen to be in close orbit around the supermassive black hole that lurks at the center of the Milky Way, known as Sagittarius A* (Sgr A*).
In this illustration, stars are seen to be in close orbit around the supermassive black hole that lurks at the center of the Milky Way, known as Sagittarius A* (Sgr A*). International Gemini Observatory/NOIRLab/NSF/AURA/J. da Silva/(Spaceengine) Acknowledgement: M. Zamani (NSF's NOIRLab)

To make these measurements, an international team cooperated on the project to bring together data from different instruments around the world. The researchers say that future telescopes like the Giant Magellan Telescope and the Thirty Meter Telescope will make it possible to make even more precise measurements.

“We will improve our sensitivity even further in future, allowing us to track even fainter objects,” concluded Gillessen. “We hope to detect more than we see now, giving us a unique and unambiguous way to measure the rotation of the black hole.”

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