Astronomers operating an antenna called EDGES in the Australian outback reported that radio waves of a particular frequency were significantly dimmer than other waves coming from the night sky. The discovery was heralded as a landmark signal from the birth of the first stars after the Big bang, which should have stamped such a signature in the light.
The dip in the radio spectrum observed by EDGES looked very different from what had been predicted. The data suggested that the early universe was cold and caused a lot of theoretical activity.
The result of the search for the EDGES dip using a radio antenna was published in February by the team at the Raman Research Institute in Bangalore, India. The astronomer set the antenna on a pair of remote lakes in India in early 2020, cutting their data collection short and returning to Bangalore hours before the first Covid lockdown began. The SARAS team found no trace of the dip observed by EDGES after analyzing their data.
If it were on the sky, it should have been reproduced in their data, according to a radio astronomer at the UC Berkeley.
The leader of the EDGES experiment says more work is needed to resolve the issue.
The radio waves that EDGES and SARAS aimed to detect were created by hydrogen atoms absorbing and emitting radio waves with a wavelength of 21 centimeters. Waves are stretched by the expansion of the universe during their journey to Earth. Waves from distant clouds of hydrogen expand for a longer time and reach Earth with longer wavelength waves than waves from closer clouds. The stretching of the light gives a record of events in the past.
Astronomers have been using 21-centimeter emission to study nearby galaxies for more than half a century. They have started measuring longer wavelengths, which are more obscured by radio interference, in search of emissions from hydrogen clouds deeper in the past.
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