The James Webb Space Telescope may have made the first detection of dark stars, objects that supposedly existed in the early stages of the universe and generated their energy through the decay of dark matter.
In a study published in the PNAS journal, a group of researchers has analyzed some of the oldest galaxies observed by James Webb, and for three of them has proposed an alternative explanation of their nature.
The authors suggest that the objects JADES-GS-z13-0, JADES-GS-z12-0, and JADES-GS-z11-0, which emitted their light between 320 and 400 million years after the big bang, might not be galaxies, but stellar-type punctual bodies, of great dimension, and with concentrations of dark matter in their interior: the so-called dark stars.
If confirmed, this would be a discovery of enormous importance for astrophysics, said Katherine Freese, director of the Weinberg Institute for Theoretical Physics at the University of Texas and one of the authors of the study: “The discovery of a new type of A star by itself is already a very interesting fact, but confirming that it is dark matter that powers these objects would be a huge discovery.”
Standard theoretical models propose that galaxies that formed shortly after the birth of our universe must have been composed of the first generation of stars (collectively called Population III), stars much more massive and ephemeral than the Sun. According to these models , the primitive galaxies must have been small compared to the current ones, since there would not have been enough time for their growth based on mergers between them.
However, observations made during the first year of operation of the James Webb have challenged this model. Some of the oldest galaxies imaged by the instrument, which emitted their light a few hundred million years after the big bang, appear brighter than expected.
These discrepancies have aroused interest in the scientific community, and some studies have suggested that the model of galaxy formation may need to be revised in depth.
But there is another possible explanation: some of the objects captured by the Webb telescope might not be galaxies. According to Freese, “if some of these objects were actually dark stars, our simulations of galaxy formation would agree better with observations.”
Dark stars would be huge spherical structures, with masses equivalent to millions of suns, and composed mainly of hydrogen and helium, the two most abundant components in the universe and which also form ordinary stars. However, unlike these, dark stars would also contain dark matter inside, which would give them unique properties.
There are two types of matter in the universe. The ordinary, composed of atoms, which is what constitutes everything we see in the cosmos, such as galaxies, stars or planets. The second type of matter is called dark matter, which dominates in an approximate ratio of 6 to 1 over ordinary matter, which is not made up of atoms, and whose nature is still unknown.
Dark matter would be made up of fundamental particles that have not yet been discovered, and one of the most widespread hypotheses is based on the existence of so-called WIMPs (weakly interacting massive particles). Models predict that these particles would decay by mutual interaction (that is, they would function as their own antiparticles).
Ordinary stars, like the Sun, balance the pressure generated by their own weight with the source of energy within, energy released by nuclear fusion processes that run throughout the star’s lifetime.
However, the dark stars, although enormous, would be very sparse, so that the temperatures necessary to ignite the engine of nuclear fusion could not be reached in their interiors. Its energy source would be the disintegration process of dark matter particles.
One of the most interesting features of the putative dark stars is that they would show a point appearance in observations by James Webb. That is, unlike galaxies, they would not reveal any form.
This has been precisely one of the aspects analyzed by the team of researchers from the University of Texas, which has found that the three suspected objects, initially identified as galaxies, are compatible with point light sources.
But according to the authors of the study, new, much more precise observations will be necessary to confirm the existence of dark stars. In particular, detailed light analysis should show characteristic traces in the spectrum of these objects.
And the detection of the typical concentric rings that point light sources generate around them when they are observed through telescopes, called Airy disks, would be clear evidence.
