Ancient Universe “warmed up” before it “lit up”
Astronomers hunting for evidence of the light from the first stars and galaxies have found that the Universe was warm, rather than cold, before it “lit up”.
The Curtin University-led team from the International Centre of Radio Astronomy Research was searching for the elusive ‘Epoch of Reionisation’, using the Murchison Widefield Array telescope, which is a period early in the Universe’s history that is predicted by theory but is yet to be detected using radio telescopes.
It signifies the end of the Cosmic Dark Ages, roughly a billion years after the Big Bang, when the gas between galaxies shifted from opaque to transparent, allowing light from the first stars and galaxies to travel throughout the Universe.
Dr Nunhokee explained that to study this early period of the Universe, astronomers must isolate the faint signal from the Epoch of Reionisation, identify and remove every other source of radio waves in the Universe from their observations.
The quality and quantity of this new dataset are what made this discovery possible, according to the team. A cold Universe would have produced a signal that would have been visible due to the MWA’s extensive capabilities. The lack of that signal rules out such a ‘cold start’ to reionisation and means the Universe must have been ‘pre-heated’ before reionisation happened.
The initial paper “Limits on the 21cm power spectrum from MWA observations” was published in The Astrophysical Journal on August 8th last year.