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New dawn for South African radio astronomy as major telescope nears completion

30 Sep 2021
HERA radio telescope
The Hydrogen Epoch of Reionization Array is a radio telescope that consists of 350 dishes packed closely together that point straight up at the sky. (Courtesy: Daniel Jacobs)

A $25m radio telescope in South Africa that is dedicated to observing the early universe is expected to be complete early next year. Nearly six years after construction began, the remaining dozen 14 m-diameter dishes belonging to the Hydrogen Epoch of Reionization Array (HERA) will be installed over the coming months. It will then aim to study the first galaxies and black holes in the universe.

The signal we are trying to detect has travelled over 13 billion light-years to reach us, so we need a big telescope in order to receive enough signal to detect it

David DeBoer

Funded by several institutions as well as the US National Science Foundation, the Gordon and Betty Moore Foundation, HERA is situated next to MeerKAT in the arid Karoo region, near Carnarvon in the Northern Cape province. Using a 350 antenna-array of 14 m dishes, HERA’s primary science goal will be studying the “Epoch of Reionization”. This occurred about 13 billion years ago when the universe was still young and is the period when the first stars and galaxies formed.

The first billion years of cosmic history are shrouded in mystery and the shroud only began to lift when ultraviolet light from the first stars and galaxies ionized the fog of neutral hydrogen gas that filled the universe. HERA will allow scientists to probe this epoch directly.

HERA currently has the best sensitivity to measure the tiny radiation emitted from hydrogen atoms that is used to observe the epoch and this month HERA released the first set of observations in 2017–2018 using about 50 dishes.

“The signal we are trying to detect has travelled over 13 billion light-years to reach us, so we need a big telescope in order to receive enough signal to detect it,” says David DeBoer, HERA project manager and an astronomer at the University of California, Berkeley. “The data taken to-date with the first antennas is allowing us to place some limits, but not actually detect our elusive signal. When done, and when we’ve sufficiently understood the complex details, we expect to detect the signal over may times and many different spatial scales.”

Dawn of an HERA

When complete, HERA will have enough collecting area to quickly detect this signal from far away in the universe. The full HERA array will also be able to probe the universe even further back in time before the stars started to ionize the universe, known as the “cosmic dawn”.

“It will tell us something fundamental about the initial processes of star formation and about cosmology in the early universe, just a mere hundreds of million years after the Big Bang,” says Mario Santos of the University of Western Cape and the South African Radio Astronomy Observatory, who sits on HERA’s board. “But such detection will require very sophisticated signal processing and analysis techniques as well as lots of computing power that are being developed hand in hand with construction of the telescope.”

South Africa currently has several research groups that are working on HERA’s data and its theoretical interpretation. “As we are able, we will make the data public and provide some tools for its use,” says DeBoer.

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