At the center of almost every galaxy around us, we found \nsuper-massive black holes with a mass of million or billion times that \nof the Sun. In our galaxy, the Milky Way, there is a black hole with \nabout 4 million solar masses. Some of these black holes are active and \ndevour huge amounts of gas, irradiating their own host galaxy. Others, \nlike the Milky Way one, are more quiet.<\/p>\n\n\n\n
Current theories successfully describe the formation process of small\n black holes, up to tens of solar masses. These objects are formed with \nthe collapse of stars more massive than the Sun, at the end of their \nlife. From small black holes, of \u201cstellar mass\u201d, it is possible to form \nsuper-massive black holes through a growth process, accreting gas from \nthe surrounding environment or merging with other black holes. \nNonetheless, this process requires a long time, billion years, to \nfinally reach the size of super-massive black holes.<\/p>\n\n\n\n