A special cluster of stars swirling around the violent center of the Milky Way could become “immortal” by constantly capturing and destroying dark matter particles in their cores, a new study suggests.
Scientists found this out using computer simulations of the evolution of stars dark matter particles captured by the gravity of these stars can often collide and “annihilate” inside the star, transforming into ordinary particles, releasing significant amounts of energy in the process.
This additional energy source could keep the star stable, potentially making it immortal, even after its regular supply of nuclear fuel dries up, the researchers suggest.
“Stars burn hydrogen nuclear fusion“, the lead author of the study Isabelle John, a doctoral student in astroparticle physics at Stockholm University, told Live Science via email. “The outward pressure from this balances the inward pressure of gravitational forces and keeps the stars in a stable equilibrium.”
However, many stars seen near the Milky Way’s central black hole appear to be much younger than the theories of stellar evolution predict. To investigate this mystery, scientists tested whether stars can draw energy from the rich supply of dark matter believed to exist in the galactic center.
“Our simulations show that if stars can collect large amounts of dark matter that annihilate inside the star, this can provide a similar outward pressure that makes the star stable due to dark matter annihilation rather than nuclear fusion – so stars can use dark matter as fuel instead of hydrogen,” said John. “The important difference is that stars use up their hydrogen, which eventually causes their death. Stars, on the other hand, can accumulate dark matter continuously.”
Studies, published on the arXiv preprint server in May, has not yet been reviewed.
Stars defying theory
Stellar evolution is a well-studied subject. The relationships between the star’s age, luminosity, size, and temperature have been derived with high precision from both theory and astronomical data. However, recent observations have shown that the properties of stars near the center Milky Way defy the generally accepted theory of stellar evolution.
Related: Baby stars that defy explanation ‘swarm like bees’ around Milky Way’s supermassive black hole
“The innermost stars of our Galaxy, the S cluster stars, exhibit a number of properties that [are] we don’t find anywhere else: It’s not clear how they got so close to the center, where the environment is thought to be rather hostile to star formation,” explained John. “They also appear to be much younger than would be expected if stars were formed there moved from elsewhere. Moreover, there seem to be an unexpected number of heavy stars.”
These strange properties of S cluster stars can be explained by the presence of another source of energy in them. For example, this extra source of energy could allow the star to burn hydrogen—the usual energy source—at a slower rate, causing it to age more slowly and appear younger than it actually is.
In his recent study, John along with Tim Linden Stockholm University and Rebecca K. Leane from the SLAC National Accelerator Laboratory at Stanford University suggested that this source could be the annihilation of dark matter particles. This explanation is consistent with the fact that a larger amount of dark matter is believed to be hiding in the center of the galaxy, exactly where the freak stars have been observed.
“In most of the Milky Way, the density of dark matter is not high enough to affect the stars,” John said. “But in the Galactic Center the amount of dark matter is very high, potentially many billions of times higher than on Earth.”
Virtual destruction
To test their hypothesis, the scientists performed a computer simulation of the life cycle of a star surrounded by a cloud of dark matter with a density equal to that of the galactic center. They hypothesized that dark matter is composed of weakly interacting matter particles, one of the primary candidates for the components of dark matter.
Since dark matter particles have not yet been found in laboratory experiments, the strength of their interaction with ordinary matter and the rate at which they annihilate each other are not known. However, the study showed that for certain values ​​of these quantities, the dark matter-based energy production mechanism perfectly explained the observed properties of the stars in the S cluster.
However, to confirm their explanation, the authors believe that more stars need to be discovered near the galactic center. In addition, more precise measurements of the parameters of known stars must be made in order to reliably compare observations with theoretical predictions. Hopefully, such observations will be possible in the near future with the Very Large Telescope in Chile or the Keck Observatory in Hawaii, the researchers said.
“More precise observations of S cluster stars will give us more information about these stars and the processes going on,” John said. “This will show whether the observations are consistent with our simulations, or whether other explanations for their unusual properties become more favorable.”