First discovered 60 years ago, quasars can shine as bright as a trillion stars in avolume the size of our Solar System. Over the decades since they were first observed, it has remained a mystery what could trigger such powerful activity.
The new work has now revealed that it is a consequence of the collision of galaxies. The Milky Way is likely to experience its own quasar when it collides with the Andromeda galaxy in about 5 billion years. The study has been an important step forward in our understanding of how these powerful objects are triggered and powered.