Furthermore, the stars in Triangulum II are observed to have different metallicities, indicating multiple episodes of star formation. This shows that the galaxy has to be many times more massive than the total mass of all its stars in order for its gravity to keep in all the gas and dust that were dispersed from past episodes of star formation to form new generations of stars.
Although dark matter is few times more abundant than ordinary matter in the Universe, it has never been directly observed. The existence of dark matter is inferred by its gravitational influence in galaxies and clusters of galaxies. It is believed that the particles that make up dark matter can annihilate one another when they collide to produce gamma rays that can be detected. However, detecting these gamma ray signals is challenging because other astrophysical objects and phenomena also generate gamma rays.
Triangulum II is a very quiet galaxy and it is not forming any new stars. As a result, Triangulum II, with its high concentration of dark matter, may be a good and pristine place to search for gamma ray signals from annihilating dark matter particles, hopefully shedding more light on the nature of dark matter.
Kirby et al. (2015), “Triangulum II: Possibly a Very Dense Ultra-Faint Dwarf Galaxy”, arXiv:1510.03856 [astro-ph.GA]