Galactic ’hailstorm’ in the early Universe

Astronomers have been able to peer back to the young Universe to determine how quasars - powered by supermassive black holes with the mass of a billion suns - form and shape the evolution of galaxies. While gas is launched out of the quasar at very high temperatures, there is enough time for some of it to cool through radiative cooling - similar to how the Earth cools down on a cloudless night - Tiago Costa Two teams of astronomers led by researchers at the University of Cambridge have looked back nearly 13 billion years, when the Universe was less than 10 percent its present age, to determine how quasars - extremely luminous objects powered by supermassive black holes with the mass of a billion suns - regulate the formation of stars and the build-up of the most massive galaxies. Using a combination of data gathered from powerful radio telescopes and supercomputer simulations, the teams found that a quasar spits out cold gas at speeds up to 2000 kilometres per second, and across distances of nearly 200,000 light years - much farther than has been observed before. How this cold gas - the raw material for star formation in galaxies - can be accelerated to such high speeds had remained a mystery. Detailed comparison of new observations and supercomputer simulations has only now allowed researchers to understand how this can happen: the gas is first heated to temperatures of tens of millions of degrees by the energy released by the supermassive black hole powering the quasar. This enormous build-up of pressure accelerates the hot gas and pushes it to the outskirts of the galaxy.