Scientists Are Getting Better at Detecting Signals from the Very Early Universe

Detecting a signal from the early universe is key to understanding how stars were originally formed.
Chris Young
An image of the Epoch of Reionisation by the DRAGONS programmeCredit: Paul Geil and Simon Mutch

Scientists are getting better at detecting a signal that has been traveling across the universe for 12 billion years. This could provide great insight into the formation of the earliest stars to have come into existence.

The data is being collected by the Murchison Widefield Array (MWA), a collection of over four thousand antennas set in remote Western Australia.


Understanding the Epoch of Reionisation

In a paper that will soon be published in The Astrophysical Journal, a team led by Dr. Nichole Barry from Australia's University of Melbourne and the ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3-D) will report a great improvement on data gathered by the Murchison Widefield Array (MWA).

The team states that the MWA has improved its data output by 10 times its previous output.

The antenna collection stared operating in 2013 and was built to detect electromagnetic radiation emitted by neutral hydrogen. Neutral hydrogen made up a great part of the early universe at the time when disconnected protons and neutrons spawned by the Big Bang were starting to cool down.

Scientists Are Getting Better at Detecting Signals from the Very Early Universe
Dr Nichole Barry at The Murchison Widefield Array (MWA). Source: Ruby Byrne

The very first stars in the universe were formed when these hydrogen atoms began to come together. This phase of the universe's early evolution is known as the Epoch of Reionisation (EoR).

"Defining the evolution of the EoR is extremely important for our understanding of astrophysics and cosmology," Dr. Barry in a press release. "So far, though, no one has been able to observe it. These results take us a lot closer to that goal."

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Detecting neutral hydrogen

The neutral hydrogen prominent in the early universe during the EoR period is still detectable today. Originally, it radiated at a wavelength of approximately 21 centimeters. Now, the wavelength has widened to somewhere above two meters due to the expansion of the Universe.

Though detecting this signal can tell us a lot about the early days of the cosmos, it is extremely difficult to do so.

"The signal that we're looking for is more than 12 billion years old," explains co-author Associate Professor Cathryn Trott, from the International Centre for Radio Astronomy Research at Curtin University.

"It is exceptionally weak and there are a lot of other galaxies in between it and us. They get in the way and make it very difficult to extract the information we're after."

The team of researchers has been working on separating the original signal from contamination. By examining 21 hours of raw data from the MWA, the team explored new ways to refine the analysis and remove sources of signal contamination, including ultra-faint interference generated by radio waves on Earth.

"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," Professor Trott explained. "That it happened very rapidly is now ruled out. That the conditions were very cold is now also ruled out."

Dr. Barry says the results have established a framework from which to continue further research on the EoR period and the early formation of stars.

"We have about 3000 hours of data from MWA," she explains. "This approach will let us identify which bits are most promising, and analyze it better than we ever could before."

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