Astronomers have tracked a dramatic "changing-look" active galactic nucleus (AGN) whose central supermassive black hole appeared to switch off and then rapidly reignite. The galaxy, HE 1237−2252, dimmed in X-rays by a factor of 17 within just 18 months before recovering again. The paper outlining its analysis was uploaded to the arXiv preprint server on May 8. ...read more read less