Near-infrared flare from Galactic Centre (lightcurve)

This image displays the "light curve" of a light flare from the galactic centre, as observed in the K-band (wavelength 2.2 µm) on June 16, 2003. This and a second flare discovered about 24 hours earlier show variability on a time scale of a few minutes and appear to show larger variations (arrows) with a 17-minute periodicity. The rapid variability implies that the infrared emission comes from just outside (the event horizon of) the black hole. If the periodicity is a fundamental property of the motion of gas orbiting the black hole, the Galactic Centre black hole must rotate with about half the maximum spin rate allowed by General Relativity. The present observations thus probe the space-time structure in the immediate vicinity of that event horizon.