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The "cosmic dawn" occurred when the first stars formed, roughly 100
million years after the Big Bang. Detecting radio waves from this
period of the Universe's history is extremely challenging, as they are
drowned out by radio waves from within, and beyond, our Galaxy, human
technology, and the detectors themselves.
In 2018, the Experiment to Detect the Global EoR (Epoch of
Reionization) Signature (EDGES) reported the presence of a feature
in the radio spectrum obtained with their detector at the Murchison
Radio-Astronomy Observatory that resembled the signature of the Cosmic
Dawn. The so-called Sagan standard states that "extraordinary claims
require extraordinary evidence," and the EDGES result has inspired a
number of efforts to duplicate the result. The latest was reported in
Nature Astronomy this week. The team from India, Canada, and
Australia made observations with the Shaped Antenna Measurement of the
Background Radio Spectrum 3 (SARAS 3) radiometer on a lake in India,
and found no evidence of the spectral feature seen in the EDGES data.
Scientific progress is often two steps forward and one step back, and
sometimes one step forwards and two steps back! Further searches for
evidence of the Cosmic Dawn are underway, and the SKA-Low telescope
will enable far more sensitive searches to be made later this decade.
The image above shows the monocone SARAS3 antenna.
(Image credit:
Singh et al. preprint.)
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