Mysterious Dark Matter

What was discovered over 75 years ago, has not been detected using electromagnetic radiation, dominates the mass budget of the universe, and is filled with concrete?

       Give up?

This mysterious substance is dark matter (I threw the concrete in just to make it hard).

However, a massive new simulation showing how dark matter behaves in galaxies may shed light on ways astronomers can detect gamma rays from dark matter collisions in our Milky Way Galaxy (MWG).

Although scientists do not understand the nature of dark matter, most believe that it is some sort of undiscovered subatomic particle. One popular candidate theory argues that each particle we know (like electrons, quarks, neutrinos, etc.) also has a supersymmetric partner particle. During the early history of the universe, these supersymmetric particles would have been produced in abundance. As the universe cooled, production would have ceased and the heavier particles have decayed to lighter supersymmetric particles. According to the theory, the lightest of these particles should be stable and, therefore, is one of the leading dark matter candidates.

However, even the lightest supersymmetric particle will annihilate when it collides with its antiparticle, and this annihilation will produce a pair of gamma rays. Thus, where the density of dark matter is large enough, astronomers should see a gamma-ray signal. Previous studies argued that clumps of dark matter in galaxies will produce the strongest signal. A recent simulation reveals that the smooth dark matter halo of a galaxy should give off the most gamma rays.

These results are important because NASA recently launched the Fermi Gamma-ray Space Telescope. One of the primary motivations for this mission was to “search for signs of new laws of physics and what composes the mysterious dark matter.” Knowing where to look and what sort of signal to expect greatly facilitates this search.

As it currently stands, dark matter represents one of the many parameters of this universe that exhibit fine-tuning. RTB expects future discoveries about the nature of dark matter (both from space and in particle accelerators) to reveal this design in more detail.