A new class of black hole, more than 500 times the mass of the Sun, has been discovered by an international team of astronomers 290 million light years from Earth providing a key clue to the formation of supermassive black holes that exist at the centers of all known galaxies in the universe.

Until now, identified black holes have been either super-massive (several million to several billion times the mass of the Sun) in the centre of galaxies, or about the size of a typical star (between three and 20 Solar masses).

The new discovery is the first solid evidence of a new class of medium-sized black holes. The team, led by astrophysicists at the Centre d'Etude Spatiale des Rayonnements in France, detected the new black hole with the European Space Agency's XMM-Newton X-ray space telescope.