As we gaze into the night sky, we see a star-filled Universe. But not all of them can be seen. It turns out that the Universe may be filled with invisible “boson stars” that are made up of exotic matter that does not emit light.

Dark matter, according to scientists, makes up about 25% of the mass and energy of the Universe. However, despite much circumstantial evidence, its nature remains a mystery. Scientists have long assumed that dark matter is made up of particles known as weakly interacting massive particles (WIMPs). According to supersymmetry theories, they would have masses similar to the heaviest known particles, such as the top quark, but would remain nearly invisible.
Despite decades of research, direct evidence for the existence of WIMP has not been found to date. This prompted scientists to turn their attention to another hypothetical particle, the axion.
What are axions?
Axions appeared as an attempt to solve the symmetry problem in the strong nuclear interaction. It obeys two symmetries: charge and parity. The scientists hypothesized that these symmetries can be explained through a new quantum field that is related to the strong interaction. Axion became the embodiment of this field. The particle got its name in honor of the detergent brand, because it “cleared” the symmetry problem.
If axions exist, they could be ideal candidates for dark matter. These particles have extremely small masses — trillions of times less than the mass of a neutrino. Therefore, their quantum-wave nature manifests itself on huge scales, up to the size of a galaxy.
In addition, axions are related to bosons, a type of particle that can be in the same quantum state. This allows them to form super-dense clusters under gravity, which can resemble stars.
Invisible “boson stars”
“Boson stars” are imaginary objects that can be formed from axions. They are completely invisible, because they emit no light and have almost no interaction with ordinary matter. In terms of mass, such luminaries can be similar to ordinary luminaries or so massive that they encompass the nuclei of galaxies.
The possible existence of such objects has both advantages and challenges for science. On the one hand, “bosonic stars” could explain the effect on nuclear fusion in ordinary luminaries or explode in supernova-like events. On the other hand, it will be extremely difficult to detect them, as they are practically invisible.
For now, axions remain a hypothesis, but the search for them continues. Even if these particles do not turn out to be the source of dark matter, they will open new horizons in the study of the fundamental properties of the universe.
It is fascinating to think that in deep space there may exist invisible, “silent stars” formed by exotic matter. This is another proof of how mysterious and unexplored our universe is.
According to space.com