A team of scientists have discovered the first ever sample of dark matter after using radio wave signals to trace the universe's oldest stars.
The scientists, from Tel Aviv University and Arizona State University researchers, had teamed up on a study to investigate the formation of the universe.
However, unexpectedly, they came across "dark matter", a type of matter that does not interact with light. Because of this, it is often invisible and hard to trace.
According to the researchers, this is the "first direct proof that dark matter exists". They said the matter is formed of "low-mass particles" and is the "building block of outer space".
Dark matter remains one of the greatest mysteries in physics. To solve it, we must travel back in time
They claim that normal matter and dark matter interacted in the early universe. The signals they picked up suggest that dark matter emerged 180 million years after the formation of space.
Professor Barkana, from Tel Aviv University, said that researchers can gain a better understanding of the universe's history and its materials by studying dark matter.
"Dark matter is the key to unlocking the mystery of what the universe is made of. 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," said the academic.
He added that while scientists have attempted to study dark matter in the past, they have been unable to work out what the substance it actually is.
"Dark matter remains one of the greatest mysteries in physics. To solve it, we must travel back in time. Astronomers can see back in time, since it takes light time to reach us," explained Barkana.
This surprising signal indicates the presence of two actors: the first stars, and dark matter
"We see the sun as it was eight minutes ago, while the immensely distant first stars in the universe appear to us on earth as they were billions of years in the past."
The researchers identified the matter when they picked up a 78 megahertz radio signal, claiming that this is "largely consistent with expectations".
Barkana added: "I realised that this surprising signal indicates the presence of two actors: the first stars, and dark matter.
"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."
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