Evidence of cosmic climate change found

Evidence of an intense warming period in universe`s early history has been found by a team of astronomers.

Last Updated: Nov 03, 2010, 17:52 PM IST

London: 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, 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, a Cambridge University release said.

Astronomers found a clear indication that temperature increased steadily between the period when 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, the release said.

Cambridge University astronomer George Becker, who led the study, said, "Early in history of Universe, majority of matter was spread out in a very thin gas that filled up all of space. The gas casts a series of shadows on light given off byquasars, which are extremely distant, bright objects. By analysing how those shadows block he background light from the quasars, we can infer many properties of the absorbing gas."

The quasar light, the astronomers looked at, was more than 10 billion years old by the time it reached Earth it had travelled through vast tracts of the Universe. Therefore each
intergalactic cloud the light passed through during this period left an imprint and the cumulative effect can be used as fossil record of temperature in early Universe.

The temperatures were massive compared with standard Earth temperature. The research suggests that one billion years afterBig Bang, the gas was a "cool" 8,000 degrees Celsius. By three and half billion years, it had climbed to at least 12,000 degrees.

This warming trend is believed to run counter to normal cosmic climate patterns, as normally the Universe is expected to cool down over time. To create observed rise in
temperature, something substantial must have been heating the gas. Astronomers believe that climate change was caused by huge amount of energy coming from young, active galaxies during this epoch.

Martin Haehnelt, who also took part in the research, said, "The likely culprits are the quasars themselves. These objects, which are thought to be giant black holes swallowing
up material in centres of galaxies, emit huge amounts of energetic ultraviolet light. These UV rays would have interacted with intergalactic gas, creating the rise in temperature we observed."

PTI