Black hole in the core of a galaxy. Hubble Space Telescope (HST) image of a disc of dust and gas circling a black hole in the galaxy NGC 4261. The dust disc is the dark oval shape at centre, and is about 800 light years across. This has a faint spiral form shown by slightly brighter 'arms' within the disc. Spectroscopic measurements reveal that the dust and gas is swirling around a very massive core. The object, about 1.2 billion times the mass of our Sun, is a black hole. This feature was first discovered by the HST in 1992, but can now be studied in more detail following the HST servicing mission of 1994.