The fascinating discovery could turn what we know about galaxy formation on its head.
The precise nature of dark matter and dark energy, which are thought to account for up to 96% of the observable universe, remains one of the most important unsolved mysteries in modern physics.
Despite concerted efforts, astronomers have been unable to observe dark matter directly because it does not absorb, emit or reflect any electromagnetic radiation, thus making it impossible to see.
It is, however, believed to play a vital role in the formation of new galaxies.
Now though, the discovery of a galaxy that appears to completely devoid of dark matter has called even this into doubt, suggesting that we know even less about galaxy formation than we realized.
The galaxy in question, which is known as AGC 114905, is an ultradiffuse galaxy (UDG) – meaning that while it is as large as the Milky Way, it is much fainter and has far fewer stars.
Situated 250 million light years away, it is the first galaxy ever observed to have no dark matter at all.
Exactly why this should be, as well as what this means for our understanding of how galaxies form, currently remains unclear.
“In principle, galaxies like this shouldn\’t exist,” said study lead author and astronomer Pavel Mancera Pina from the University of Groningen in the Netherlands.
“We cannot effectively explain them with any existing theory.”