The early universe could be home to huge stars powered by dark matter annihilation instead of fusion – and the James Webb Space Telescope may have already found some
By Leah Crane
17 July 2023
These three objects were originally identified as galaxies but they may actually be “dark stars”
NASA/ESA
The James Webb Space Telescope (JWST) may have spotted weird stars powered by dark matter instead of nuclear fusion. If these stars are really out there, it could solve three major cosmic mysteries in one fell swoop.
Regular stars form when a cloud of dust and gas becomes so massive that it collapses in on itself, and the pressure and temperature in the centre are high enough to begin the process of nuclear fusion, wherein atoms slam together and merge into heavier elements. So-called dark stars wouldn’t have any fusion at all – in the early universe, they could form from similar clouds rich in dark matter. For several postulated types of dark matter, when two particles collide they should annihilate in a blast of energy, which would be intense enough to power a supermassive star.
“They’re very bizarre stars – in radius they’re around 10 AU [astronomical units, the distance between Earth and the sun], so they’re puffy beasts, and there’s no core,” says Katherine Freese at the University of Texas at Austin. “They’re relatively cool throughout, and because they’re so cool there’s nothing that’s preventing accretion onto them, so they grow – they can grow to a million solar masses, a billion solar luminosities, maybe even more.”
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Freese and her colleagues hunted through data on some of the most distant objects JWST has seen and found three of them that could potentially be supermassive dark stars, not galaxies as was initially assumed. JWST has found many more distant galaxies than expected, which could be a problem for our standard model of cosmology, so if some of them are actually dark stars it could solve that dilemma.
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The hunt for dark matter: The universe's mysterious gravitational glue
“Right now the spectra are not really good enough to tell – you’d have to look at one of these objects for a year with JWST, which is not likely to happen,” says Freese. The other way to figure it out would be to find a dark star with its light magnified by gravitational lensing, which could give us much more information.