During the 1970s, while probing distant galaxies to determine their mass, size, and other characteristics, astronomers noticed something interesting. When examining the rate at which these galaxies rotated (their rotational curves), they found that the outer parts were rotating faster than expected. In short, their behavior suggested that they were far more massive than they appeared to be. This led to the theory that in addition to stars, gas, and dust, galaxies were surrounded by a “halo” of mysterious, invisible mass – what came to be known as Dark Matter (DM).
It was famed astronomer Vera C. Rubin, for whom the Vera C. Rubin Observatory (formerly the LSST) is named, who first proposed that DM played an important role in galactic evolution. Astronomers have since theorized that DM haloes must have existed shortly after the Big Bang and were integral to the formation of the first galaxies. In a recent study, an international team examined the core regions of two galaxies that existed 13 billion years ago. Their observations confirmed that DM dominated the haloes of these quasars, offering fresh insight into the evolution of galaxies in the very early Universe.
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