THE MILKY WAY’S SUPERMASSIVE BLACK HOLE’S SHINING MOMENT

Our galaxy’s supermassive black hole, Sagittarius A* (Sgr A*), is famously one of the dimmest to exist, but new data from the JAXA/ESA/NASA X-Ray Imaging and Spectroscopy Mission (XRISM) space telescope suggests it hides a violent past. By observing the molecular cloud G0.11-0.11 in the Galaxy with XRISM’s Resolve instrument, astronomers now estimate that Sgr A* experienced a massive flare approximately 200 years ago.

For decades, scientists have debated whether the glow of such clouds was caused by cosmic-ray bombardment or reflected light from Sgr A*. XRISM’s high-resolution spectra has now settled the debate for G0.11-0.11. It rules out the cosmic ray-model by revealing an absence of specific X-ray wavelengths that would be generated by the cosmic rays.

Instead, the data confirms the cloud is acting as a cosmic mirror, providing a ‘light echo’ of an ancient outburst. During this ancient outburst event, the black hole reached a luminosity at least ten times brighter than its current quiescent state.

By studying these delayed echoes across multiple clouds, astronomers can finally reconstruct a detailed timeline of our black hole’s explosive evolution.

“This is an exciting new capability and a brand-new toolbox for developing these techniques,” says Stephen DiKerby, postdoctoral researcher at Michigan State University.

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www.science.org/doi/10.1126/science.adv9266