By Christine Cuénod
The University of KwaZulu-Natal (UKZN) is part of an international team working on data emerging from the world-class Hydrogen Epoch of Reionization Array (HERA) telescope. The release of the team’s first set of observations is providing a glimpse of what the universe looked like 13 billion years ago.
The HERA network consists of an array of closely packed 14-metre diameter dishes and 350 antennae situated next to the MeerKAT radio telescope in the Northern Cape. From here, HERA can observe large scale structures in the universe during and before the epoch of reionization - a time when the neutral intergalactic medium, comprised largely of neutral hydrogen atoms, was ionised by the emergence of luminous sources, giving rise to plasma, the most abundant form of matter in the universe.
The substantial collecting area allows for increased sensitivity and robust statistical characterisation, and enables the first measurements of the universe’s large-scale neutral hydrogen structure.
Led from the United States, the large international collaboration features strong South African participation, from construction to scientific research. HERA is hosted by the South African Radio Astronomy Observatory (SARAO), which oversees construction management, systems engineering, its location, power and fibre networks.
Constructed by a team of local artisans from Carnarvon in the Northern Cape, the sky-facing, state-of-the-art antennae are made from surprisingly simple materials: wooden poles, a PVC-pipe structure and wire mesh. Construction has taken place over the past six years, with observations happening throughout, and completion is expected in a matter of weeks.
The deceptively simple set-up allows astronomers to peer deeper into the universe than ever before, and HERA is helping astronomers understand how the universe reached conditions for the very first stars and galaxies to form.
The radio telescope looks even further back in time than that achieved by leading optical and infrared space telescopes. Scientists from UKZN, Rhodes University and the University of the Western Cape are among the experts interpreting the data that HERA produces.
Professor Yin-Zhe Ma of UKZN’s Astrophysics Research Centre (ARC) and School of Chemistry and Physics, whose expertise includes radio cosmology and 21cm intensity mapping of the scale of the universe in the epoch of reionization, co-authored one of the papers accompanying the release of HERA’s Phase I data.
Following research revealing the most sensitive upper limits identified to date on the strength of the signal it is possible to detect from the universe at around 66 million years after the Big Bang, Ma and other authors elaborated on the implications of those upper limits for models of early universe star and galaxy formation.
These two papers present clear observational evidence for heating of the intergalactic medium by energy from stars in the epoch of reionization - and as HERA’s capabilities are extended, the measurement of the very first stars to emerge even before this epoch will be possible.
As the project reaches completion, engineers are confident that HERA will enable astronomers to observe the birth of the very first stars that appeared after the Big Bang, and investigate the proposed new physics believed to have affected these stars.