Stars at the centre of the Milky Way are so densely packed that special imaging techniques (such as adaptive optics) were needed to boost the resolution of the VLT. Thanks to these techniques, astronomers were able to watch individual stars with unprecedented accuracy as they circled the Galactic Center. Their paths conclusively demonstrated that they were orbiting in the immense gravitational grip of a supermassive black hole nearly three million times more massive than the sun. The VLT observations also revealed flashes of infrared light emerging from the region at regular intervals. While the cause of this phenomenon is unknown, observers have suggested that the black hole may be spinning rapidly.