Fri, Mar 02, 2018 - Page 6 News List

Cosmic dawn when the stars switched on glimpsed

AP, WASHINGTON

An artist’s rendering of how the first stars in the universe might have looked is pictured in an undated handout image.

Photo: Reuters / N.R. Fuller / US National Science Foundation

After the Big Bang, it was cold and black.

Then there was light.

Now, for the first time, astronomers have glimpsed that dawn of the universe 13.6 billion years ago when the earliest stars were turning on the light in the cosmic darkness and if that is not enough, they might have detected mysterious dark matter at work, too.

The glimpse consisted of a faint radio signal from deep space, picked up by an antenna that is slightly bigger than a refrigerator and costs less than US$5 million, but in certain ways can go back much farther in time and distance than the celebrated, multibillion-dollar Hubble Space Telescope.

Judd Bowman of Arizona State University, lead author of a study in published in the journal Nature on Wednesday, said the signal came from the very first objects in the universe as it was emerging out of darkness 180 million years after the Big Bang.

Seeing the universe just lighting up, even though it was only a faint signal, is even more important than the Big Bang because “we are made of star stuff and so we are glimpsing at our origin,” said astronomer Richard Ellis, who was not involved in the project.

The signal showed unexpectedly cold temperatures and an unusually pronounced wave.

When astronomers tried to figure out why, the best explanation was that elusive dark matter might have been at work.

If verified, that would be the first confirmation of its kind of dark matter, which is a substantial part of the universe that scientists have been searching for for decades.

“If confirmed, this discovery deserves two Nobel Prizes” for both capturing the signal of the first stars and potential dark matter confirmation, said Harvard astronomer Avi Loeb, who was not part of the research team.

Cautioning that “extraordinary claims require extraordinary evidence,” he said independent tests are needed to verify the findings.

Bowman agreed independent tests are needed, even though his team spent two years double and triple-checking their work.

“It’s a time of the universe we really don’t know anything about,” Bowman said.

He said the discovery is “like the first sentence” in an early chapter of the history of the cosmos.

It is nothing that astronomers could actually see, but it was all indirect, based on changes in the wavelengths produced by radio signals.

The early universe was dark and cold, filled with just hydrogen and helium.

Once stars formed, they emitted ultraviolet light into the dark areas between them. That ultraviolet light changes the energy signature of hydrogen atoms, Bowman said.

Astronomers looked at a specific wavelength.

If there were stars and ultraviolet light, they would see one signature. If there were no stars, they would see another.

They saw a clear, but faint signal showing there were stars, probably many of them, Bowman said.

Finding that trace signal was not easy because the Milky Way galaxy alone booms with radio wave noise 10,000 times louder, said Peter Kurczynski, advanced program technology director for the US National Science Foundation, which helped fund the research.

“Finding the impact of the first stars in that cacophony would be like trying to hear the flap of a hummingbird’s wing from inside a hurricane,” Kurczynski said in a foundation video.

Because the high end of the frequency they were looking at is the same as FM radio, the astronomers had to go to the Australian desert to escape interference.

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