The easiest way to spot a supermassive black hole (SMBH) is when it expels a huge jet of matter in one of the most energetic displays in the Universe. While astronomers have spotted these huge black holes at the centers of most galaxies, not all are active—meaning the jet isn't there, and the SMBH is hiding. However, even inactive black holes may give themselves away if we can spot them eating stars: the disruption of a star by gravitational forces can produce a burst of light.
As reported in Nature, the Pan-STARRS1 (PS1) galaxy survey spotted a burst of intense ultraviolet and visible light from the center of a galaxy with no known SMBH. S. Gezari et al. performed a spectral analysis on the flare, and determined it to be consistent with the destruction of a red giant star with a helium-rich core. The likely culprit for the star's disruption is a black hole with a mass between 2.7 and 2.9 million times that of our Sun.