In a groundbreaking discovery, scientists say they have found a signal from some of the earliest stars in the universe, giving us an unparalleled glimpse into the dawn of the cosmos.
The signals originate from hydrogen gas from just 180 million years after the Big Bang, itself 13.8 billion years ago. It suggests that the first generation of stars in the universe formed around this time.
A study describing the findings, 12 years in the making, is published in Nature.
"Finding this miniscule signal has opened a new window on the early universe,” Judd Bowman from Arizona State University, the study’s lead author, said in a statement.
"Telescopes cannot see far enough to directly image such ancient stars, but we've seen when they turned on in radio waves arriving from space."
About 400,000 years after the Big Bang, our universe was a dark place devoid of stars and galaxies. But over the next 100 million years, gravity began to pull gas together, until it collapsed to form the first stars. When these burst into life, they brought the universe out of its so-called dark ages and began the Epoch of Reionization (EoR).
Our current best telescopes have only been able to see stars dating back to about 300 million years after the Big Bang. While we haven’t seen the stars directly here, it is indirect evidence for their existence, something that is certain to open up whole new avenues of research.
From the detection we cannot tell much about the stars themselves, such as their size or mass. However, it’s hoped that future detections building on this research may be able to do just that, and give us a better idea of what they looked like.
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.