London, May 16 : A team led by Raghunathan Srianand of the Inter-University Centre for Astronomy and Astrophysics in Pune, India, has measured what the temperature of the Universe was 11 billion years ago, when it was just a fifth its current age.
According to a report in New Scientist, the team measured the cosmic microwave background (CMB) to find out the temperature of the early universe.
CMB is radiation that heats up gas clouds, which are the coldest objects in the universe that fill the space between stars and galaxies.
The hot plasma that filled the universe a mere 380,000 years after the big bang, which took place an estimated 13.7 billion years ago, emitted this radiation.
But as the universe expanded, the electromagnetic waves that comprise this radiation were stretched to longer wavelengths and lower energies, decreasing the radiation's temperature.
Today, that temperature is just 2.7 K.
Now, the team led by Raghunathan Srianand has measured what the CMB temperature was 11 billion years ago, when the universe was just a fifth its current age.
They found it to be a chilly 9.15 K (about -264 degree C) back then, with an uncertainty of 0.7 K in either direction.
"That is in excellent agreement with the 9.3 K temperature predicted in the big bang scenario," said team member Patrick Petitjean of the Institut d'Astrophysique in Paris, France.
The astronomers arrived at their figure by a very indirect route. What they actually measured was the temperature of carbon monoxide gas in a galaxy about 11 billion light years away.
The gas was detected by the way it intercepts light from an even more distant object called a quasar - a bright galaxy whose central black hole is consuming its surroundings.
The team used the Very Large Telescope (VLT) array in Paranal, Chile, to measure the wavelengths where the carbon monoxide absorbs the quasar's light. The wavelengths affected depend on the temperature of the galaxy's gas, whose heat is thought to come from the CMB.
According to Charles Bennett, chief scientist for NASA's Wilkinson Microwave Anisotropy Probe (WMAP) mission, which measures the CMB, it is important to make such measurements to test scientists' expectations.
"It's nice to see consistent things in different ways," he told New Scientist.