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The dark stars would be composed mostly of normal matter, like modern stars, but a high concentration of neutralino dark matter present within them would generate heat via annihilation reactions between the dark-matter particles. This heat would prevent such stars from collapsing into the relatively compact and dense sizes of modern stars and therefore prevent nuclear fusion among the 'normal' matter atoms from being initiated.[1]

Under this model, a dark star is predicted to be an enormous cloud of molecular hydrogen and helium ranging between 1 and 960 astronomical units (AU) in radius and with a surface temperature and luminosity low enough that the emitted radiation would be invisible to the naked eye.[1][2]

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In the unlikely event that dark stars have endured to the modern era, they could be detectable by their emissions of gamma rays, neutrinos, and antimatter and would be associated with clouds of cold molecular hydrogen gas that normally would not harbor such energetic, extreme, and rare particles.[3][2]

The remaining 26 percent of the universe is dark matter. According to some predictions, hundreds of these dark matter particles zip through your body every second. Fortunately for us, this type of matter, though it follows the laws of gravity, does not interact with the baryons our bodies are composed of. Unfortunately for researchers, this makes it extremely difficult to study. Dark matter emits no light, so it can only be probed indirectly through its gravitational fingerprints, such as the way it bends light around massive galaxies. For the most part, researchers must rely heavily on models to make informed predictions about the nature of this elusive material.

Back then, the universe was a denser and more compact place, and the WIMP partners tangoed with tenacity, continually annihilating each other in energetic blasts. During this time, WIMPs may have been swept up in the gravitational clutches of giant gas clouds. And as these clouds condensed to form early stars, they would have taken the WIMPs along for the ride.

Rindler-Daller studies dark stars with computer models, specifically looking at ways the stars might pulsate. Many stars periodically expand and contract, causing their light to pulse, and dark stars might show this behavior as well. Comparing different models, Rindler-Daller discovered that different masses of WIMPs would lead to different periods of variability in the dark stars. If observed, these pulsations could be one way to measure the mass of WIMPs.

These false-color images captured by the Hubble Space Telescope compare the distribution of normal matter (red) to dark matter (blue) in the universe. The map covers an area of the sky nine times larger than the Full Moon, making it one of the best maps of dark matter ever obtained.

No current telescope is powerful enough to see a dark star in the early universe. But this will soon change. The James Webb Space Telescope, the successor to the Hubble Space Telescope, is set to launch in 2021. With a 6.5-meter primary mirror and special instruments built for capturing infrared light, the James Webb should be able to see protogalaxies and dark stars, should they exist, in the early universe.

Additionally, the next generation of ground-based telescopes, with mirrors 30 meters across, is at the drawing board. Infrared detectors on these telescopes could easily peer into the dusty interior of our galaxy. Astronomers may be able to find hidden near the center of the Milky Way old white dwarfs and neutron star WIMP burners whose lives have been extended, thanks to dark matter accretion.

Regardless, the concept of dark stars has stuck with Freese. Over the past 16 years, she and her colleagues have refined their understanding of these tantalising hypothetical objects. The problem was, finding evidence for them always seemed out of reach.

A team of three astrophysicists -- Katherine Freese at The University of Texas at Austin, in collaboration with Cosmin Ilie and Jillian Paulin '23 at Colgate University -- analyzed images from the James Webb Space Telescope (JWST) and found three bright objects that might be "dark stars," theoretical objects much bigger and brighter than our sun, powered by particles of dark matter annihilating. If confirmed, dark stars could reveal the nature of dark matter, one of the deepest unsolved problems in all of physics.

"Discovering a new type of star is pretty interesting all by itself, but discovering it's dark matter that's powering this -- that would be huge," said Freese, director of the Weinberg Institute for Theoretical Physics and the Jeff and Gail Kodosky Endowed Chair in Physics at UT Austin.

Although dark matter makes up about 25% of the universe, its nature has eluded scientists. Scientists believe it consists of a new type of elementary particle, and the hunt to detect such particles is on. Among the leading candidates are Weakly Interacting Massive Particles. When they collide, these particles annihilate themselves, depositing heat into collapsing clouds of hydrogen and converting them into brightly shining dark stars. The identification of supermassive dark stars would open up the possibility of learning about the dark matter based on their observed properties.

Follow-up observations from JWST of the objects' spectroscopic properties -- including dips or excess of light intensity in certain frequency bands -- could help confirm whether these candidate objects are indeed dark stars.

Confirming the existence of dark stars might also help solve a problem created by JWST: There seem to be too many large galaxies too early in the universe to fit the predictions of the standard model of cosmology.

"It's more likely that something within the standard model needs tuning, because proposing something entirely new, as we did, is always less probable," Freese said. "But if some of these objects that look like early galaxies are actually dark stars, the simulations of galaxy formation agree better with observations."

The three candidate dark stars (JADES-GS-z13-0, JADES-GS-z12-0, and JADES-GS-z11-0) were originally identified as galaxies in December 2022 by the JWST Advanced Deep Extragalactic Survey (JADES). Using spectroscopic analysis, the JADES team confirmed the objects were observed at times ranging from about 320 million to 400 million years after the Big Bang, making them some of the earliest objects ever seen.

"When we look at the James Webb data, there are two competing possibilities for these objects," Freese said. "One is that they are galaxies containing millions of ordinary, population-III stars. The other is that they are dark stars. And believe it or not, one dark star has enough light to compete with an entire galaxy of stars."

"We predicted back in 2012 that supermassive dark stars could be observed with JWST," said Ilie, assistant professor of physics and astronomy at Colgate University. "As shown in our recently published PNAS article, we already found three supermassive dark star candidates when analyzing the JWST data for the four high redshift JADES objects spectroscopically confirmed by Curtis-Lake et al, and I am confident we will soon identify many more."

The idea for dark stars originated in a series of conversations between Freese and Doug Spolyar, at the time a graduate student at the University of California, Santa Cruz. They wondered: What does dark matter do to the first stars to form in the universe? Then they reached out to Paolo Gondolo, an astrophysicist at the University of Utah, who joined the team. After several years of development, they published their first paper on this theory in the journal Physical Review Letters in 2008.

Together, Freese, Spolyar and Gondolo developed a model that goes something like this: At the centers of early protogalaxies, there would be very dense clumps of dark matter, along with clouds of hydrogen and helium gas. As the gas cooled, it would collapse and pull in dark matter along with it. As the density increased, the dark matter particles would increasingly annihilate, adding more and more heat, which would prevent the gas from collapsing all the way down to a dense enough core to support fusion as in an ordinary star. Instead, it would continue to gather more gas and dark matter, becoming big, puffy and much brighter than ordinary stars. Unlike ordinary stars, the power source would be evenly spread out, rather than concentrated in the core. With enough dark matter, dark stars could grow to be several million times the mass of our sun and up to 10 billion times as bright as the sun.

Dark stars are stars in every sense, in that the immense gravity of their cold, infalling material is perfectly balanced by outward hydrostatic pressure, generated by energy-releasing processes in their interiors. All the same, Freese says that they have several key distinctions from regular stars.

To search for evidence of SMDSs, the trio examined data from the JWST Advanced Deep Extragalactic Survey (JADES). In the survey, they looked for evidence of light at certain wavelengths being absorbed by candidate stars. In particular, they were interested in the 1640 nm helium-II absorption line which is often observed in the spectra of hot, bright stars.

The three candidate dark stars are JADES-GS-z11-0, JADES-GS-z12-0 and JADES-GS-z13-0. Astronomers participating in the James Webb Space Telescope Advanced Deep Extragalactic Survey (JADES) spotted them in December 2022. They thought, originally, these objects were galaxies, or collections of ordinary stars, not unlike our own Milky Way.

[It] originated in a series of conversations between Freese and Doug Spolyar, at the time a graduate student at the University of California, Santa Cruz. They wondered: What does dark matter do to the first stars to form in the universe?

Scientists believe [dark matter] consists of a new type of elementary particle. And the hunt to detect such particles is on. Among the leading candidates are Weakly Interacting Massive Particles. When they collide, these particles annihilate themselves, depositing heat into collapsing clouds of hydrogen and converting them into brightly shining dark stars. 17dc91bb1f