Scientists say they are closer than ever to seeing the dawn of the universe.
Astronomers hoping to spot the super-faint signal of the beginnings of the first stars and galaxies are still yet to actually detect it – but they say they are getting closer to actually detecting it.
The signal that scientists are looking for is the beginning of the Epoch of Reionization, or EoR, which happened 12 billion years ago. That marks the moment when the first stars formed and galaxies began taking shape and the first lights in the universe started to switch on, and marks the beginning of the cosmos that surrounds us now.
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Despite it being a foundational moment in the history of the universe, very little is known about the EoR. But we have a rough sense of what probably happened.
In the beginning, the first atoms formed were positively charged hydrogen ions, which were eventually brought together with hydrogen atoms to form neutral hydrogen, which was all that filled the universe at its very beginning. Those atoms then began to clump together, slowly forming stars and galaxies that re-ionized the neutral hydrogen.
Researchers were looking for the very faint signal of that neutral hydrogen, which dominated the universe when it was dark. They did not find it but set a new limit on its strength, letting scientists know how strong that signal could be.
“We can say with confidence that if the neutral hydrogen signal was any stronger than the limit we set in the paper, then the telescope would have detected it,” said Jonathan Pober, an assistant professor of physics at Brown University and corresponding author on the new paper. “These findings can help us to further constrain the timing of when the cosmic dark ages ended and the first stars emerged.”
If scientists were able to detect that signal, they could measure how it changed in its beginning and understand the story of the EoR. That would teach them about how the cosmos began, and started to construct the universe we see today.
But they are still unable to actually see that signal. As such, they are trying to isolate it with more and more precise and sensitive instruments.
One of the difficulties is hearing it amid the crashing noise of the world. The neutral hydrogen radiation comes out at 21 centimeters, but has stretched over 12 billion years to 2 meters, and scientists are tuned in to that wavelength.
But many other sources give out the same signal, from televisions to natural sources within the Milky Way.
“All of these other sources are many orders of magnitude stronger than the signal we’re trying to detect,” Pober said in a statement. “Even an FM radio signal that’s reflected off an airplane that happens to be passing above the telescope is enough to contaminate the data.”
Scientists now hope to keep making that process more precise, with the aim of catching sight of that signal.
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