Astronomers close in on extremely messy clue to evolution of the universe

9 Sep 2019

Neutral hydrogen (red) gradually ionised by the first stars (white) in an image of the Epoch of Reionisation. Image: Paul Geil and Simon Mutch

Astronomers have said they’re closing in on a truly ancient signal that will hopefully reveal the mystery behind the life and death of the first stars.

One of the largest arrays of its kind has helped researchers from Australia’s University of Melbourne and the ARC Centre of Excellence for All-Sky Astrophysics in 3 Dimensions (ASTRO 3D) uncover important discoveries in the evolution of our universe.

In a paper soon to be published to The Astrophysical Journal, it was revealed the Murchison Widefield Array (MWA), containing more than 4,000 antennas in remote Western Australia, has detected the trail of a signal that has travelled across the universe for 12bn years. The MWA was designed specifically to detect electromagnetic radiation emitted by neutral hydrogen, which comprised most of the young universe after the Big Bang.

These hydrogen atoms eventually clumped together to form the very first stars in an era referred to as the Epoch of Reionisation (EoR). According to Dr Nichole Barry, defining the evolution of this era is “extremely important for our understanding of astrophysics and cosmology”.

Narrowing the possibilities

While the neutral hydrogen radiated at wavelengths of approximately 21cm during the EoR, the stretching of the universe over billions of years has also seen the signal expand to more than two metres, making it incredibly difficult to detect and extremely messy when trying to discern it from the rest of the universe.

However, using 21 hours of raw data taken from the MWA and new techniques to refine it into tangible information, the researchers were able to significantly reduce the range in which the EoR may have begun.

Co-author of the research, associate professor Cathryn Trott, said: “We can’t really say that this paper gets us closer to precisely dating the start or finish of the EoR, but it does rule out some of the more extreme models.

“That it happened very rapidly is now ruled out. That the conditions were very cold is now also ruled out.”

Barry went on to say that the results obtained in this latest study are a step forward in humanity’s global quest to explore the infant universe, but they will also lead to further research.

Colm Gorey was a senior journalist with Silicon Republic