Distant galaxy contains no dark matter, study reports

Astronomers have spotted a galaxy without dark matter, a discovery that could rapidly change the common perceptions of galaxy formation.
By Joseph Scalise | Apr 03, 2018
For the first time in history, researchers have detected a galaxy that does not have any dark matter, according to a new study in the journal Nature.

Dark matter is a mysterious substance that, while abundant in the universe, cannot be studied because it emits no light and no energy. While it is assumed to be a key part of all galaxies, the new research -- which comes from researchers at Yale University -- challenges that belief.

The galaxy, known as NGC1052-DF2, sits 65 million light years from Earth. It has no gas and few stars. Despite that, it is roughly the same size as the Milky Way and is classified as a ultra-diffuse galaxy.

Dark matter is thought to comprise roughly a quarter of the universe's combined mass and energy and 80 percent of its total mass. However, it has never been directly observed. Scientists simply believe it exists based on the gravitational effect it has on certain galaxies.

"There's about five times more dark matter in a galaxy than regular matter," explained Michelle Collins, a physicist at the University of Surrey who was not involved in the study, according toBBC News reports. "As you go further out from the galaxy you have fewer stars and more dark matter. The dark matter halo is much more extended than the stars are in a galaxy."

By finding a galaxy without dark matter, the team now has evidence there are systems that can form without it. That changes the common perception on how systems form and could force astronomers to reevaluate the current models of galaxy formation.

"We really thought that this is the essence of what a galaxy is, that galaxies are built from, initially, a bunch of dark matter and that all the stars and all the planets and everything else is just a little frost on top," said lead author Pieter van Dokkum, a professor at Yale University, according to Reuters.

Though researchers are not sure howNGC1052-DF2 formed without dark matter, they believe there is a chance that a large event swept away all the dark matter it had, or that a nearby galaxy altered it in some way. More research needs to be done to follow up on such claims.

