[https://www.theatlantic.com/science/archive/2021/01/galactic-calamity-10000-lightyears-away/617611/](https://www.theatlantic.com/science/archive/2021/01/galactic-calamity-10000-lightyears-away/617611/) Giant bubbles hovering over the Milky Way seem to be remnants of an ancient explosion.

[https://www.theatlantic.com/science/archive/2021/01/galactic-calamity-10000-lightyears-away/617611/](https://www.theatlantic.com/science/archive/2021/01/galactic-calamity-10000-lightyears-away/617611/) The alternative culprit is the supermassive black hole that sits at our galaxy’s heart. The leviathan is about 4 million solar masses—i.e., 4 million times the mass of our sun—and lately, it’s been relatively quiet. But if a large cloud of gas once strayed too close, the black hole could have switched on like a spotlight.