Signals From Ancient Stars Could Provide Clues About Dark Matter

Thursday, 01 March 2018 - 8:04PM
Space
Astronomy
Thursday, 01 March 2018 - 8:04PM
Signals From Ancient Stars Could Provide Clues About Dark Matter
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Flickr/Smithsonian Institution
Just the other day, news broke that radio signals created by some of the earliest stars in the universe had finally reached Earth after 13.6 billion years.

This was an especially big deal on its own, but looking at the radio waves showed something unusual which conflicts with our current understanding of how the early universe worked: the radio waves dipped in a way that suggested energy was being absorbed, but that dip was twice as large as astronomers expected.

For the radio signal to act that way, it would suggest that twice as much energy was absorbed, which means cosmic gas in the early universe cooled much faster than anybody expected. And assuming you've read the headline, you might guess that the best explanation for what was cooling the universe would be dark matter.



More research into the matter still needs to be done, but dark matter is one of the only known substances that could be colder than early cosmic gasses. The early universe was extremely hot following the Big Bang, and there's nothing else we know of that has bizarre enough properties to stay cold in that environment.

These properties in the ancient radio waves were first picked up by Arizona State University and MIT's joint project, the Experiment to Detect the Global Epoch of Reionization Signature, or "EDGES". According to Rennan Barkana of Tel Aviv University, who explained the process in a study published in Nature:

Opening quote
"The extra cooling indicated by the data is possible only through the interaction of the [gas] with something even colder. The only known cosmic constituent that can be colder than the early cosmic gas is dark matter."
Closing quote





Dark matter is still a contentious subject in astronomy, largely because its not well understood. It's thought to be more common in the universe than any regular matter, even though we can't seem to properly detect it and we haven't observed any instances of it interacting with other matter. Indeed, the evidence for its role here doesn't directly point to dark matter, it simply eliminates everything else we know of except dark matter.

So the big hole in this theory is that in order to cool the early cosmic gas, dark matter would have to interact with it, and we don't know how that would work. But this is solid evidence, and it's something new for scientists to work with.
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