Astronomers find evidence of cosmic climate change

Evidence of an intense warming period in the Universe's early history, described as a form of "cosmic climate change", has been found by an international team of astronomers. The findings, shortly to be published in the Monthly Notices of the Royal Astronomical Society, were made by researchers measuring the temperature of gas that lies in between galaxies. They found a clear indication that the temperature of this 'intergalactic medium' had increased steadily between the period when the Universe was one tenth of its current age and the point at which it reached one quarter of its current age. The team believe that the effect was caused by objects called quasars; giant accreting black holes at the heart of galaxies - which emit ultraviolet light and triggered a series of reactions in the gas clouds that caused the temperature to rise. University of Cambridge astronomer Dr. George Becker, who led the study, said: "Early in the history of the Universe, the vast majority of matter was not in stars or galaxies. Instead, it was spread out in a very thin gas that filled up all of space." "The gas casts a series of shadows on the light given off by quasars, which are extremely distant, bright objects. By analysing how those shadows block the background light from the quasars, we can infer many of the properties of the absorbing gas, such as where it is, what it's made of, and how hot it is." The quasar light the astronomers looked at was more than 10 billion years old by the time it reached Earth and had travelled through vast tracts of the Universe.