Dawn’s Early Light

A stunning era in cosmology took another leap forward this week when scientists announce that they have detected light from the first stars in the universe—light that was generated more than 13 billion years ago—and a mere 180 million years after the Big Bang, essentially a blink in the history of time. It is the furthest back in time that scientists have ever been able to investigate.

Nature broke the news on Wednesday, noting that the signals, picked up by a radio telescope in Western Australia, also hint at presence of dark matter. This excellent Nature graphic indicates the time period that caused the new observations.

It was a breakthrough discovery for Rennan Barkana, a cosmologist working with the help of a Templeton grant appropriately titled “From Cosmic Dawn to the Present: Searching for the First Stars and for Direct Evidence of Dark Matter.”

This week’s findings yielded a little bit of both. The strength of the signal was so strong, “I was actually quite amazed,” Barkana told Nature, second, where he also published a related paper in Nature. Barkana explained that the signal’s strength indicates either more radiation than expected in the cosmic dawn, or the gas was cooler than predicted. Barkana surmises that the gas was cooled by something, which he believes points to dark matter. (More on dark matter below.)

“This is the first time we’ve seen any signal from this early in the Universe, aside from the afterglow of the Big Bang,” Judd Bowman, an astronomer at Arizona State University who led the work, said in a statement.

Keith Bannister, astronomer at Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO), told CNN, “It’s very exciting to see our baby stars being born. (Although) we can’t see the stars themselves, we’re seeing the effect they have on the gas around them.”

“To my mind … it’s Nobel Prize-worthy twice, if it’s real,” Avi Loeb, a theoretical astrophysicist at Harvard University who was not involved in the research, told the Los Angeles Times. “Not only did they detect the signal, but it actually is bigger than one can accommodate in the standard cosmological model. And you need new physics in order to explain a signal as big as they detected.”

Peter Kurczynski of the National Science Foundation discusses the significance of the findings here:

About that dark matter

Barkana is quoted frequently in an NPR report from NPR titled, “Did Dark Matter Make The Early Universe Chill Out?”

“Dark matter is a very big mystery,” Barkana tells NPR. “We know it’s most of the matter in the universe, but we have no idea about its properties.” Scientists haven’t seen dark matter, only its effects on gravity.

Barkana “began to think about dark matter in the context of the first stars, and did some calculations,” writes NPR science correspondent Nell Greenfieldboyce. “His work suggests the hydrogen gas could be cooled by interactions with dark matter particles that are relatively light, as opposed to the heavier mass people have been theorizing.”

But what is exactly is “dark matter”? Barkana explains in this little animated video:


(Artist’s rendering at top of page by N.R.Fuller, National Science Foundation)