The international Hydrogen Epoch of Reionisation Array (Hera) telescope, being constructed in South Africa’s radio astronomy reserve in the Karoo region, in the Northern Cape province, has received a significant new cash injection that will fund a major expansion of the array, SKA South Africa (SKA SA) announced recently. SKA SA is one of the partners in the Hera programme. The new grant is worth $5.8-million, and comes from the Gordon and Betty Moore Foundation. It follows a $9.5-million grant from the US National Science Foundation (NSF) in September. While the NSF grant ensures that Hera will have 240 antennas by 2018, this new grant will, in due course, increase that figure to 350. Construction of the array started in 2015 and, so far, 35 of the 14-metre-diameter dishes have been erected.

Hera is intended to gather data from shortly after the birth of the universe, when the first stars, galaxies and black holes developed. The first generation of stars were hot and massive, and they and the first black holes flooded space with X-rays. This period is known as the Epoch of Reionisation. It started about 400-million years after the Big Bang. The universe is now about 13.77-billion years old.

“Observations at the lowest radio frequencies (< 100MHz) allow for observations of the epoch that precedes cosmic reionisation, where X-rays are expected to have heated the intergalactic medium,” explained SKA SA Hera senior astronomer Dr Gianni Bernardi. “As X-rays are expected to be generated by accretion on black holes, observations of this epoch will directly probe the properties of the first black holes formed in the universe.” (Black holes are surrounded by accretion disks composed of gas, dust and other matter. These are accelerated to incredible speeds by the tremendous gravity of the black hole, with the result that they release heat, gamma rays and X-rays as the various particles of matter in the disks collide with one another.)

“The new funding increases the sensitivity of Hera by adding 110 dishes – 350 dishes in total,” he pointed out. “This increase in collecting area provides the sufficient sensitivity to attempt imaging large ionised bubbles [of hydrogen in the intergalactic medium] rather than measuring ‘only’ their statistical properties.”

Hera is composed of a closely packed array of fixed parabolic dishes that form the reflector elements. Each is centred on a concrete hub. These hubs serve to constrain PVC spars, arranged in a radial pattern, which are tensioned against a rim into an approximately parabolic shape. The rim is supported by utility (basically, telephone) poles. The surface of the reflector is formed by welded mesh panels, which are installed on the radial spars.

This year will see an acceleration in the construction tempo for the array to some 100 dishes a year. This will involve five teams working in parallel. The team leaders are five local residents who were recruited when the programme started in 2015 and have been trained to lead and train the new team members. It is hoped that the members of all the teams will be residents of the Karoo.

“In excess of R1.7-million has been spent thus far with local suppliers in the Karoo to purchase the material with which the telescope is being built,” reported Hera Karoo project engineer Kathryn Rosie. “We are proud of the fact that all the build materials, items and labour involved in the construction of the reflector elements have been sourced from within South Africa, with most of our bulk materials being sourced from within the Karoo region.”

Hera is classified as a pathfinder for the SKA Phase 1 low frequency array (SKA1 LOW). Perhaps ironically, SKA1 LOW will be hosted by Australia, South Africa being the base for the SKA Phase 1 midfrequency array. ‘SKA’ stands for Square Kilometre Array and will be the world’s biggest radio telescope when Phase 1 is completed.

In addition to SKA SA, the partners in Hera are, in the US, the National Radio Astronomy Observatory, Arizona State University, Brown University, the Massachusetts Institute of Technology, the University of California, at Berkeley, the University of California, at Los Angeles, the University of Pennsylvania and the University of Washington. In Italy, the partner institution is the Scuola Normale Superiore of Pisa and, in the UK, Cambridge University. South African universities associated with the programme are KwaZulu-Natal, the Western Cape and the Witwatersrand, as well as Rhodes University.