Space signal offers peek at dawn of universe
Might also offer insight on dark matter at work
WASHINGTON — After the Big Bang, it was dark and cold. And then there was light. Now, for the first time, astronomers have glimpsed that dawn of the universe 13.6 billion years ago.
And if that’s not enough, they may have detected mysterious dark matter at work, too.
The glimpse consisted of a faint radio signal picked up by an antenna that is slightly bigger than a refrigerator and costs less than $5 million but in certain ways can go back much farther in time and distance than the Hubble Space Telescope.
Judd Bowman of Arizona State University, lead author of a study in Wednesday’s journal Nature, 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 may 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 over 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 wasn’t part of the research team. Cautioning that “extraordinary claims require extraordinary evidence,” he said independent tests are needed to verify the findings.
The early universe was black 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.
Because the high end of the frequency they were looking in is the same as FM radio, the astronomers had to go to the Australian desert to escape interference.
They then labored to confirm what they found, in part by testing it against dummy signals in the lab, and it all showed that what they spotted was the existence of the first stars, Bowman said.
So far, the scientists know little about these early stars. They were probably hotter and simpler than modern stars, Ellis and Bowman said. But now that astronomers know where and how to look, others will confirm this and learn more, Bowman said.
The research does not establish when these stars turned on, except that at 180 million years after the
Big Bang, they were on. Scientists had come up with many different time periods for when the first stars switched on, and 180 million years fits with current theory, said Ellis, a professor at University College London.