Evidence of cosmic climate change

The Universe may have gone through a warming trend early in its history. That is what a team of astronomers have discovered by measuring the temperature of the gas that lies in between galaxies. They found that the temperature had progressively increased over the period from when the Universe was one tenth to one quarter of its current age. Most likely this cosmic climate change was caused by the energy output from young and active galaxies during the epoch. Results are presented in a paper to be published in the journal Monthly Notices of the Royal Astronomical Society (RAS).

"Early in the history of the universe, the vast majority of matter was not in stars or galaxies", explains George Becker astronomer at University of Cambridge. It was spread out in the gas that filled up all of space, he says in RAS news release. The team of astronomers, led by Becker, measured the temperature of this gas using the light from quasars.

"Just as Earth's climate can be studied from ice cores and tree rings, the quasar light contains a record of the climate history of the cosmos", says Becker.

The measured temperatures are different from those in the history of Earth. At 1 billion years after the Big Bang, the gas had a temperature of 8,000 Celsius degrees that increased to 12,000 Celsius degrees at three and a half billion years.  

It is known that as the Universe expands, the gas should get colder. However, something has been heating the gas.

It was the quasars that explain the warming trend. That is because they were becoming much more common and emit huge amounts of energetic ultraviolet light. "These UV rays would have interacted with the intergalactic gas, creating the rise in temperature we observed" explains Martin Haehnelt, one of the astronomers involved in research, who is also at Cambridge University's newly-established Kavli Institute for Cosmology.

Astronomers used the data taken with the 10-meter Keck telescopes in Hawaii; they also run simulations on a supercomputer at the University of Cambridge.

For more info please visit the RAS website, here.