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SKA turns up the heat

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This new-found signal marks the closest astronomers have seen to that moment

BIG BANG: A timeline of the universe, updated to show when the first stars emerged. This updated timeline of the universe reflects the recent discovery that the first stars emerged about 180 million years after the Big Bang. The research behind this timeline was conducted by Judd Bowman of Arizona State University and his colleagues, with funding from the National Science Foundation. Picture: NR Fuller National Science Foundation

The detection of a signal from the first stars to have emerged in the Universe, about 180 million years after the Big Bang, by a Square Kilometre Array (SKA) precursor telescope, has paved the way for SKA, in the Northern Cape, to make very precise measurements of the structures within the Universe during this crucial, early heating phase.

In a paper published in the journal nature last week, a team of US astronomers announced the detection of a signal from the first stars to have emerged in the Universe, about 180 million years after the Big Bang.

After the Big Bang, the universe cooled and went dark for millions of years. In the darkness, gravity pulled matter together until stars formed and burst into life, bringing the “Cosmic Dawn”.

This new-found signal marks the closest astronomers have seen to that moment.

The weak signal was detected using an antenna at the Murchison Radio-astronomy Observatory (MRO) in Western Australia, where the Northern Cape’s SKA’s future SKA-low telescope will be located, as part of the Experiment to Detect the Global EoR (Epoch of Reionization) Signature or EDGES.

“Finding this miniscule signal has opened a new window on the early universe,” lead author Dr Judd Bowman, of Arizona State University, said.

At 78 MHz, in the FM radio station range, the detection would be impossible from most ground-based sites in the world.

However, the MRO site, located some 800 kilometres north of Perth, benefits from extreme radio-quietness, an asset that is protected by legislation to ensure a radio-quiet zone of up to 260 km. This allows to keep human-made activities that produce interference such as radio stations, mobile phones and electronics, to a minimum.

The MRO was developed by CSIRO for its Australian Square Kilometre Array Pathfinder (ASKAP) telescope and also hosts a low-frequency telescope.

These telescopes make use of the radio-quiet nature of the site and also are important precursors to the SKA.

“This is a powerful demonstration of what can be achieved with the combination of an excellent site and world-class engineering, boding well for the great discoveries that will be enabled by the SKA”, Robert Braun, Science Director at the SKA Organisation, said.

“While the EDGES team have made a detection of the ‘global signature’, that is averaged over the sky of the Cosmic Dawn, the SKA will allow very precise measurements to be made of the structures within the Universe during this crucial, early heating phase.

“It may even be possible for the SKA to form the first direct images of these structures; pointing to the locations of the very first stars and galaxies to have formed,” Braun added.