Named Nube, the galaxy is roughly the size of the Small Magellanic Cloud, a dwarf galaxy near the Milky Way that is about 19,000 light-years across and about 7 billion solar masses. However, the light it emanates is much less than would be expected.
According to their findings, Nube is the most massive ultra-diffuse galaxy (UDG) ever found. Such galaxies are believed to be so dim because of their age, which has left them with relatively few stars. Some are as large as the Milky Way but have just 1% of the stars. Nube has a stellar mass of 390 million solar masses, which is 5% of the stellar mass of the Small Magellanic Cloud, a comparable-sized galaxy.
However, Nube is vastly larger than any other known UDG - three times as wide.
In attempting to understand how and why such a bizarre galaxy formed, astronomers suggest dark matter may be to blame.
"To this end, and under the hypothesis that the distribution of stars in Nube is representative of the distribution of the dark matter halo, we found that a soliton-shaped profile (typical of fuzzy dark matter) reproduces the observed distribution of stars very well," the authors wrote.
Dark matter is a stand-in term used by astrophysicists to describe a type of matter that has not yet been directly observed, but the effects of which can clearly be seen on the surrounding matter. It has been theorized to exist because of otherwise-unexplainable behavior by stars and galaxies, which is inconsistent with the mass of observable matter known to be interacting with them.