The more we look at the universe, the more we find things that we struggle to explain with our current theories of science. And from time to time, we come across something that is remarkably unusual, but that is still within the scope of the standard cosmological model, if only for a short time.
The discovery of a pair of gigantic primordial galaxies, which existed when the universe was less than a billion years old, is in that last category. With a combined mass of approximately 313 billion soles and originating only 780 million years after the Big Bang, the pair – called SPT0311-58 – pushes against the limits of how scientists understand that galaxies were formed, especially in the early universe.
In addition to its own phenomenal mass (273 billion and 40 billion solar masses), it is also believed to exist in a halo of dark matter that envelops them. This halo is much more massive, with at least 1 trillion times the mass of the sun. As a reference, our galaxy, the Milky Way, has a mass of approximately 580 billion suns.
"Any one of these galaxies alone would be extreme, and here you have two together," Chris Hayward of the Center for Computational Astrophysics at the Flatiron Institute in New York City, who is also co-author of the article on the discovery, he said in a statement on Wednesday. "This is really pushing the limits of how massive a halo of dark matter can be at this moment in the universe, this is one of the rarest and most extreme dark matter clusters in the universe," he added.