Researchers are investigating the potential existence of exotic stars known as dark stars, which could be powered by dark matter. This groundbreaking theory may help explain some of the most enigmatic objects in the universe and provide insights into the nature of dark matter itself.
Normal stars form when a cloud of gas collapses under its own gravity, leading to nuclear fusion at their cores. In contrast, dark stars may have originated in a denser early universe, where dark matter was more abundant. If a collapsing gas cloud contained sufficient dark matter, annihilation events within that dark matter could produce enough energy to prevent the star from collapsing further, allowing it to shine.
A team led by Katherine Freese from the University of Texas at Austin has begun to investigate how such dark stars might evolve and eventually perish. Unlike regular stars, which fuse heavier elements until they exhaust their fuel and collapse into black holes, dark stars follow a different path. According to George Fuller from the University of California, San Diego, a dark star could continuously grow by accumulating dark matter, effectively avoiding the nuclear evolution that leads to instability.
Despite their unique properties, dark stars are not immune to the laws of physics. Based on Albert Einstein‘s theory of general relativity, the gravitational fields of massive objects do not simply increase with mass. Eventually, a dark star could reach a tipping point, becoming unstable and collapsing into a black hole. The researchers estimate that this collapse could occur at masses ranging from 1,000 to 10 million times that of the sun.
This mass range positions dark stars as potential candidates for explaining the formation of supermassive black holes, which astronomers have observed at astonishingly early moments in the universe’s history. According to Freese, the rapid formation of a black hole from a 100-solar-mass seed to one weighing a billion solar masses poses a significant challenge if these black holes were formed from conventional stars.
Dark stars might serve as the massive seeds for these supermassive black holes. Moreover, the James Webb Space Telescope (JWST) has detected two mysterious classes of distant objects dubbed “little red dots” and “blue monsters.” Initial analyses suggest that these objects could be either individual dark stars or compact galaxies, but their extraordinary distances make conventional formation scenarios difficult to reconcile with the time available in the early universe.
Freese and her colleagues calculated that if the little red dots and blue monsters are indeed dark stars, there should be a distinct signature in their emitted light. This signature would indicate a specific wavelength that dark stars would absorb, a characteristic that regular stars cannot exhibit due to their high temperatures. Some preliminary observations by JWST hinted at this light absorption, but the data lacks the clarity needed for definitive identification.
Freese remarked, “Right now, all the candidates that we have, there are two things that could fit the spectra equally well: one supermassive dark star or an entire galaxy of regular stars.” The team continues to pursue clearer evidence for the existence of dark stars.
Experts like Dan Hooper from the University of Wisconsin-Madison emphasize the significance of this research. While current findings do not provide conclusive evidence of dark stars, they represent a crucial step towards understanding these cosmic phenomena. “This isn’t some profound, unambiguous smoking gun, but it’s a really well-motivated thing that they’re looking for,” Hooper explained.
To confirm the existence of dark stars, further observations with improved sensitivity will be necessary. However, it remains uncertain whether JWST can achieve the detail required to identify such distant objects. Volodymyr Takhistov from the High Energy Accelerator Research Organization stated that confirming dark stars would be a remarkable achievement, offering new avenues for exploring fundamental physics.
The implications of discovering dark stars extend beyond mere curiosity. If these stars indeed contribute to the formation of supermassive black holes, they could help unravel the mysteries surrounding dark matter, which remains one of the least understood components of the universe. The mass at which dark stars collapse into black holes could provide critical information regarding the properties of dark matter particles.
As research continues, scientists remain hopeful that the elusive dark stars could shed light on some of the universe’s most profound questions. “If these things are out there, they’re rare,” said Hooper. “Rare, but extraordinary.”
