Webb Telescope captures tantalizing evidence of mysterious ‘dark stars’

By Will Dunham

WASHINGTON (Reuters) – Scientists for the past 15 years have searched for evidence of a type of star only hypothesized but never observed – one powered not by the fusion of atoms like the sun and other ordinary stars, but by a mysterious substance called dark matter.

Thanks to the ability of the James Webb Space Telescope to go back to the dawn of the universe, the first good candidates for being “dark stars” have been identified.

The three objects spotted by Webb, which launched in 2021 and began collecting data last year, were originally identified last December as some of the earliest known galaxies in the universe but, researchers say, could instead be huge black stars.

Dark matter, invisible matter whose presence is primarily known through its galactic-scale gravitational effects, is believed to be a small but crucial ingredient in dark stars. These stars are described as composed almost entirely of hydrogen and helium – the two elements present in the infancy of the universe – with 0.1% of their mass as dark matter. But self-annihilating dark matter would be their engine.

Dark matter is invisible to us – it doesn’t produce or interact directly with light – but it’s thought to make up around 85% of the matter in the universe, with the remaining 15% comprising normal matter like stars , planets, gas, dust and earthly things like pizza and people.

Dark stars would be able to reach a mass at least a million times greater than that of the sun and a luminosity at least a billion times greater, with a diameter about ten times the distance between the Earth and the sun.

“These are big, bloated beasts,” said Katherine Freese, a theoretical astrophysicist at the University of Texas at Austin and lead author of the research published in the journal Proceedings of the National Academy of Sciences.

“They’re made of atomic matter and powered by the bit of dark matter that’s inside,” Freese added.

Unlike ordinary stars, they would be able to gain mass by accumulating gas that would fall to them in space.

“They can continue to accrete surrounding gas almost indefinitely, reaching supermassive status,” said Cosmin Ilie, a Colgate University astrophysicist and lead author of the study.

They would not have been as hot as the first generation of ordinary stars in the universe. It was the nuclear fusion that took place in the cores of these stars that gave rise to elements heavier than hydrogen and helium.

The three objects identified as potential dark stars date from the start of the universe’s history – one 330 million years after the Big Bang event that sparked the cosmos 13.8 billion years ago. years, and the others 370 million years and 400 million years after the Big Bang. Click.

Based on Webb’s data, these objects could be either early galaxies or dark stars, Freese said.

“A supermassive dark star is as bright as an entire galaxy, so it could be either,” Freese added.

While there isn’t enough data to make a definitive judgment on these three, Freese said, Webb might be able to get more complete data on other similar primordial objects that might provide evidence.” receding” from a black star.

Conditions in the early universe may have been conducive to dark star formation, with high densities of dark matter at the locations of star-forming hydrogen and helium clouds. Such conditions are highly unlikely today.

Freese and two colleagues first proposed the existence of dark stars in 2008, basing the name on the Grateful Dead song “Dark Star” from the 1960s.

“It would be really super exciting to find a new kind of star with a new kind of heat source,” Freese said. “This could lead to the detection of the first dark matter particles. And then you can learn more about the properties of dark matter particles by studying a variety of dark stars of different masses.”

(Reporting by Will Dunham, editing by Rosalba O’Brien)

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