Unlike a disk-shaped spiral galaxy, Messier 87 has no distinctive dust lanes. It has an almost featureless, ellipsoidal shape. Luminosity diminishes with distance from the centre. At the core of this unusually large galaxy is an unusually large supermassive black hole. This is a strong source of radiation at many wavelengths, particularly radio waves. This black hole is the first and, to date, the only one for which astronomers have been able to make a direct image. A radio image taken by the Event Horizon Telescope in 2017 was published on 10 April 2019. The image shows the shadow of the black hole, surrounded by an emission ring with a diameter of .