The supermassive black hole, Sagittarius A* (Sgr A*), located at the center of the Milky Way galaxy, was not always dormant. An international X-ray spacecraft has detected evidence that Sgr A* experienced powerful flares over the last 1,000 years.
This discovery was made by the joint Japanese-European-American XRISM spacecraft (X-Ray Imaging and Spectroscopy Mission). The findings could potentially alter current understanding of how supermassive black holes, which possess masses equivalent to millions or billions of suns, evolve and influence their surrounding galaxies.
Black holes are characterized by event horizons, regions from which light cannot escape due to extreme gravity. However, matter orbiting black holes can become superheated by friction, leading to bright emissions and powerful flares. Sgr A*, with a mass equivalent to 4 million suns, was not previously known for such emissions.
Researchers identified Sgr A*'s past activity by directing XRISM at a large molecular cloud situated near the galactic center. Detailed examination of the X-rays emitted by this cloud indicated it was reflecting X-rays previously released by Sgr A* flares.
XRISM, launched in 2023, provided the precision required to measure the energies and shapes of X-ray emissions, tracking the cloud's movement and ruling out alternative explanations for its X-ray glow, such as cosmic rays.
The capabilities demonstrated by XRISM suggest its suitability for detailed studies of the universe, potentially uncovering hidden cosmic history. The research has been accepted for publication in The Astrophysical Journal Letters.