January 23, 2013
Taking Temperature Of Universe In Past Reveals Cooling Trend
Lee Rannals for redOrbit.com — Your Universe Online
An international team of astronomers from Sweden, France, Germany and Australia used the CSIRO Australia Telescope Compact Array near Narrabi to measure how warm the Universe was when it was half its current age.
"This is the most precise measurement ever made of how the Universe has cooled down during its 13.77 billion year history," Dr Robert Braun, Chief Scientist at CSIRO Astronomy and Space Science, said in a statement.
In order to take a temperature of the Universe's past, astronomers needed to look about half-way into space. Because light takes time to get from one place to another, astronomers are able to peer into the history of the Universe by observing galaxies and quasars far away.
The team studied gas in an unnamed galaxy 7.2 billion light-years away, and found that the only thing keeping this gas warm is the cosmic background radiation.
There is another powerful galaxy, a quasar referred to as PKS 1830-211, lying behind the unnamed galaxy. Radio waves from this quasar come through the gas of the foreground galaxy.
As these waves make their way through the gas, the gas molecules absorb some of the energy of the radio waves, leaving a "fingerprint" on the radio waves.
Astronomers are able to use this "fingerprint" to help them calculate the temperature of the gas. By using this technique, the astronomers learned the gas was at about 5.08 Kelvin (-450 degrees Fahrenheit), which is extremely cold, but still warmer than today's Universe. Currently, astronomers believe the temperature of the universe is about 2.73 degrees Kelvin (-454 degrees Fahrenheit).
The Big Bang theory predicts that the temperature of the cosmic background radiation drops smoothly as the Universe expands.
"That's just what we see in our measurements. The Universe of a few billion years ago was a few degrees warmer than it is now, exactly as the Big Bang Theory predicts," research team leader Dr Sebastien Muller of Onsala Space Observatory at Chalmers University of Technology in Sweden, said.