Feb. 28 (UPI) -- Astronomers say they've discovered evidence of dark matter. Scientists found the dark matter signatures while searching for the universe's first stars.
According to a team of researchers from Tel Aviv University and Arizona State University, the newly discovered signal is the product of interactions between normal and dark matter -- the first of its kind.
The signal hails from the distance universe, when the cosmos was still in its infancy -- 180 million years after the Big Bang.
"Dark matter is the key to unlocking the mystery of what the universe is made of," Rennan Barkana, head of the astrophysics department at Tel Aviv's School of Physics and Astronomy, said in a news release. "We know quite a bit about the chemical elements that make up the Earth, the sun and other stars, but most of the matter in the universe is invisible and known as 'dark matter.'"
Scientist have inferred the presence of dark matter by its gravitational effects, but direct evidence or observations of dark matter particles has eluded astronomers.
"Dark matter remains one of the greatest mysteries in physics," Barkana said.
During a survey of the most ancient light in the universe, Barkana and his colleagues discovered a unique radio wave with a frequency of 78 megahertz. The wave boasts an unexpectedly large amplitude, suggesting a greater rate of absorption at its origin -- evidence that primordial gas was colder than previously predicted.
Barkana believes the primordial gas was cooled by interactions between hydrogen atoms and cold, dark matter particles.
"I realized that this surprising signal indicates the presence of two actors: the first stars, and dark matter," Barkana said. "The first stars in the universe turned on the radio signal, while the dark matter collided with the ordinary matter and cooled it down. Extra-cold material naturally explains the strong radio signal."
Astronomers searching for dark matter have been searching for heavy particles, but the latest research -- published this week in the journal Nature -- suggests the dark matter that cooled the ancient hydrogen gas was composed of low-mass particles.
Barkana is hopeful that observatories with a large array of radio antennas will be able to locate more signals created by the first interactions between stars and dark matter.
"Such an observation with the SKA would confirm that the first stars indeed revealed dark matter," he said.