Our galaxy’s supermassive black hole is famous for being one of the dimmest in the universe. Evidence from a new space telescope shows that this might not always have been the case.

Sagittarius A*, located at the center of the Milky Way Galaxy, appears to have flared dramatically sometime within the past few hundred to 1,000 years, according to X-ray emissions observed by the XRISM space telescope. These surprising findings unveil new details of how supermassive black holes evolve. They also teach astronomers lessons about the history of our cosmic home.

Michigan State University researcher Stephen DiKerby worked with an international team to measure the X-rays coming from a giant cloud of gas near the galaxy’s center. The team examined the cloud in incredible detail thanks to XRISM’s ability to resolve the energy of individual X-ray photons. Their findings offer strong evidence that the cloud is glowing in response to a past outburst from Sagittarius A*.