A signal from the Universe's first stars, born a cosmic heartbeat after the Big Bang, has been detected for the first time, astronomers said Wednesday, setting the science world aflutter.
The observation came after a decade-long quest, years earlier than expected, and was described by one excited observer as the biggest astronomical breakthrough since the Nobel-capped detection of gravitational waves in 2015.
The findings have to be confirmed by other experiments.
Crucially, it is hoped the discovery will shed light on dark matter -- an invisible, mysterious substance thought to make up a large share of the Universe.
"Finding this miniscule signal has opened a new window on the early Universe," said Arizona State University astronomer Judd Bowman, the project's lead investigator.
"Telescopes cannot see far enough to directly image such ancient stars, but we've seen when they turned on" -- that is, sparked to life -- "in radio waves arriving from space."
Fingerprints of the stars, already active 13.6 billion years ago -- a mere 180 million years after the Big Bang gave rise to the Universe -- were picked up by a dining table-sized radio spectrometer in the Australian desert.
Such evidence had been expected, but not for years to come. To everyone's surprise, and delight, the signal contained something curious.
The early Universe, the data showed, appears to have been twice as cold as previously estimated, at minus 270 degrees Celsius (-454 degrees Fahrenheit), according to the study in Nature.
Some suggested a role for dark matter -- the theme of an accompanying science paper published by the same journal.
The author of that study, Rennan Barkana of Tel Aviv University, said the freeze might be explained by ordinary matter interacting with, and losing energy to, dark matter.
"If Barkana's idea is confirmed then we've learnt something new and fundamental about the mysterious dark matter that makes up 85 percent of the matter in the Universe, providing the first glimpse of physics beyond the Standard Model," said Bowman.