X-rays emitted from black holes sterilise galaxies

Astronomers at UCL, using ESA's Herschel Space Observatory, have shown that the number of stars that form during the early lives of galaxies may be controlled by the massive black holes at their hearts. All large galaxies have a massive black hole in the middle, each millions of times the mass of a single star. A puzzle that has remained unsolved for over a decade is that the masses of the black holes are linked to the size of the round central bulges at the hearts of galaxies. The suspicion has long been that this is due to the events in the early lives of the galaxies, when the stars in the bulge were forming. To study this phase, astronomers need to look at very distant galaxies, so far away that we see them as they were billions of years ago. "Space telescopes like Herschel let us look back in time, and that's just what we need to do to find out how today's galaxies were built" said Mat Page (UCL Mullard Space Science Laboratory). Although the black holes themselves cannot be seen, the material closest to them can get incredibly hot, emitting large amounts of light over a very wide range of wavelengths, from radio waves to x-rays.