Our cosmic evolutionary picture could be challenged by the discovery of a gigantic galaxy that appears to have no dark matter. Dark matter, which makes up about 85% of the matter in the universe, appears to be absent in galaxy NGC 1277, which is part of the Perseus galaxy cluster. Located 240 million light-years from Earth, this galaxy is the first cluster of stars, planets, dust and gas the size of the Milky Way, devoid of dark matter.

“This result is inconsistent with currently accepted cosmological models involving dark matter,” Sebastian Comeron, lead author of the discovery and a University of La Laguna researcher, said in a statement.

Dark matter is virtually invisible, as it does not interact with light like the everyday matter that composes stars, planets, and us. However, its existence can be understood through gravitational interaction. The presence of this shadowy matter was first discovered when astronomers observed massive galaxies spinning so fast that they would break apart if it were not for the gravitational force of an invisible mass holding them together.

This fact led scientists to theorize that all major galaxies are surrounded by dark matter; this is an important assumption in the development of galactic evolutionary theories. But the discovery of a galaxy that appears to have no dark matter casts doubt on this assumption.

Exploring the Antisocial Relic Galaxy

Considered a cosmic relic, NGC 1277 is unusual among galaxies as it has little interaction with other nearby galaxies. Such galaxies are considered remnants of giant galaxies that existed in the early universe. Therefore, these remnant galaxies are important in helping astronomers understand how the first galaxies formed.

To help with this line of research, Cameron and colleagues observed the remnant galaxy NGC 1277 with an instrument called an integral spectrograph. This allowed them to map the motion of the galaxy and determine its mass and how that mass is distributed.

This revealed that the distribution of the total mass of NGC 1277, which should contain dark matter, is the same as its daily matter content, in other words, the mass distribution of stars, dust, gas and planets. This means that the dark matter content in the galaxy’s radius cannot exceed 5%, but the results are more consistent with the complete absence of dark matter in NGC 1277.

This is surprising because currently popular models of cosmic evolution, including the Standard Model of Cosmology, suggest that NGC 1277 should consist of between 10% and 70% dark matter.

“This discrepancy between the observations and what we expect is confusing and perhaps even challenges the standard model,” said Ignacio Trujillo, a team member and researcher at La Laguna University.

Where did the dark matter of the relic galaxy go?

The scientists behind the discovery have few ideas as to why NGC 1277 is so devoid of dark matter.

“First, the gravitational interaction with the environment in the galaxy cluster where this galaxy is located destroys dark matter,” said Anna Ferre-Mateu, a researcher at the University of La Laguna and member of the team. “Another is that dark matter formed from the fusion of galaxy protogalactic fragments is pushed out of the system, giving rise to the remnant galaxy.”

The team was not entirely satisfied with either explanation and will therefore continue to study NGC 1277 with the William Herschel Telescope (WHT) at the Roque de los Muchachos Observatory on La Palma’s Canary Island.