These early stars were thought to be huge blue objects composed almost entirely of hydrogen with extremely short lifetimes. The result of fusion within their cores gave rise to many of the heavier elements we see today, which make up everything from planets to people. While these stars can’t be seen by telescopes, scientists had been looking for indirect evidence for their existence.
To find this evidence, the international team in this study built a small ground-based antenna called EDGES (Experiment to Detect the Global EoR Signature). The size of a table, they took this to the remote desert of Western Australia, where it would be free from radio interference from other sources.
EDGES was designed to pick up radio waves from the EoR. It’s thought that when the first stars switched on, they produced ultraviolet radiation that caused changes to surrounding clouds of hydrogen as the universe emerged from the dark ages.
This hydrogen began to emit and absorb the radiation, producing a detected frequency of 1.4 Gigahertz. Once the signal had reached Earth it had weakened to about 78 Megahertz, which the team used to calculate its age.
“With the EDGES experiment, we have detected a radio signal that is consistent with the formation of the first generations of stars in the universe, 180 million years after the Big Bang,” Raul Monsalve from the University of Colorado Boulder, one of the study's co-authors, told IFLScience.
“We are not measuring a signal that is emitted by the actual stars. What we are measuring is a signal that is emitted by the hydrogen gas that was surrounding the first stars.”
Surprisingly, the signal was found to be about twice as strong as theoretical models predicted. A second paper also published in Nature today, by Rennan Barkana from Tel Aviv University in Israel, suggests this may be due to dark matter, something that has equally amazed astronomers.
“His idea is that this could be due to a new kind of interaction between neutral hydrogen and dark matter in the universe,” explains Monsalve. “This interaction could provide new information about what dark matter is, so that is a very significant outcome.”
It’s unlikely we will ever see evidence for stars further back into the universe than this discovery, at least in our lifetimes. Thus it gives us an unsurpassed look at the beginnings of our universe, and it may answer how our cosmos went from a dark, gloomy place to one filled with the galaxies, stars, and planets we see today.