Conventional wisdom among astrophysicists dictates that galaxies don't start out with much dark matter, the unseen material that seems to make up most of the mass in the universe. Instead, they speculate, galaxies pick up dark matter over time through some unknown process.
But new observations from the McDonald Observatory in Texas have found a striking counterexample: an ancient galaxy loaded with dark matter.
The research, published Wednesday in The Astrophysical Journal, describes DSFG850.95, a galaxy 9 billion light-years away. That means the light that reaches Earth from this galaxy is 9 billion years old — providing a peek into the universe's distant past.
But unlike other ancient galaxies, DSFG850.95 is chock-full of dark matter, according to the McDonald observations.
That contrasts with the dominant theory, which is that old galaxies are "fundamentally different to galaxies in the present-day universe," Caitlin Casey, one of the researchers behind the new findings, said in a news release. "The galaxy we found is a clear counter-example of that, where it seems to have dark matter behaving in the normal way, as it does in the present-day universe."
READ MORE: Texas Astronomers Find that Dark Matter Dominates Across Cosmic Time [McDonald Observatory]
More on dark matter: Two Nearly-Identical Dark Matter Studies Have Conflicting Results