Perhaps there exists an invisible universe that includes stars, nebulae, and galaxies, yet is entirely composed of dark matter that remains hidden from our view.
Simply put, dark matter is still a mystery. Astronomers have gathered substantial independent evidence suggesting the existence of a form of matter in the universe that cannot be seen. It does not interact with light but exerts gravitational effects on ordinary matter.
The reflective universe is everywhere yet completely invisible to us. (Image source: NASA).
Dark matter holds galaxies together despite their high rotation speeds and keeps gas clusters cohesive despite high temperatures, bending the path of light and even shaping the largest structures in the universe.
Despite the evidence of its existence, the identification of dark matter particles has yet to be achieved. For decades, astronomers have asserted that there is only one type of dark matter particle in the universe. However, recently, they have begun to question whether dark matter is as abundant and diverse as matter in the ordinary universe.
For example, some high-energy physics theories predict the existence of a pair of twin particles corresponding to each ordinary particle in the dark sector. In this view, there would be dark electrons, dark quarks, dark neutrinos…, all interacting with each other through a set of forces completely foreign to those we are familiar with.
This reflective universe or “mirror” universe is everywhere yet completely invisible to us. So, how can we study this idea? This is the question posed by a group of astronomers in a paper published on arXiv. They found that surprisingly, mirror stars could make themselves visible and they would look very different from anything we have observed in the universe.
Mirror stars would form when dark matter particles interact, lose energy, and clump together. This process would occur similarly to the formation of ordinary stars, where hydrogen and helium collapse under gravitational forces, releasing energy through the emission of photons and becoming dense enough to form stars. However, these mirror stars would interact through their own forces and emit radiation—even if by releasing dark photons that we cannot see.
There could be millions, or even trillions, of dark matter stars floating solely within the Milky Way, as they are believed to account for about 80% of the galaxy’s mass.
Importantly, astronomers recognize that these mirror stars still possess gravity. This is how we know dark matter exists. Any relatively dense and massive object, whether a regular star or a mirror star, will attract matter around it. Thus, these mirror stars will pull in gas and dust drifting in the interstellar medium.
