James Webb captures evidence of dark stars – 07/17/2023 – Science

Over the past 15 years, scientists have been looking for evidence of a type of star that is still only hypothetical, and has yet to be observed — powered not by fusion of atoms, like the Sun and other ordinary stars, but by a mysterious material called dark matter.

Thanks to the ability of the James Webb Space Telescope to observe the early universe, the first good candidates to be dark stars have been identified.

The three objects detected by Webb, which launched in 2021 and began collecting data last year, were initially identified last December as some of the earliest known galaxies in the universe, but researchers say they could actually be huge dark stars.

Dark matter, invisible material whose presence is mostly known based on its galactic-scale gravitational effects, would be a small but crucial ingredient in dark stars. These stars are described as being made almost entirely of hydrogen and helium — the two elements present during the universe’s infancy — with 0.1% of their mass in the form of dark matter. But dark, self-annihilating matter would be their engine.

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

The dark stars would be capable of reaching a mass at least a million times that of the Sun and a luminosity at least a billion times greater, with a diameter approximately ten times the distance between the Earth and the Sun.

“They’re big bloated beasts,” said Katherine Freese, a theoretical astrophysicist at the University of Texas at Austin and senior author of the research published in the Proceedings of the National Academy of Sciences.

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

Unlike ordinary stars, they would be able to gain mass by accumulating the gas that is deposited on them in space.

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

They wouldn’t be as hot as the universe’s first generation of ordinary stars. It was the nuclear fusion that took place in the cores of these stars that generated elements heavier than hydrogen and helium.

The three objects pointed out as potential dark stars date from the beginning of the history of the universe – one from 330 million years after the Big Bang event, which made the cosmos rotate 13.8 billion years ago, and the others from 370 million years ago. years and 400 million years after the Big Bang.

Based on the Webb data, these objects could be either primitive galaxies or dim stars, Freese said.

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