Our picture of cosmic evolution might be thrown into doubt by the invention of a large galaxy that seems to lack dark matter.
Dark matter, which accounts for around 85% of the matter within the universe, appears to be absent from the galaxy NGC 1277, a part of the Perseus Cluster of galaxies. The galaxy, situated 240 million light-years from Earth, is the primary Milky Way-sized conglomeration of stars, planets, dust and gas found to be missing dark matter.
“This result doesn’t slot in with the currently accepted cosmological models, which include dark matter,” the leader behind the invention and University of La Laguna researcher Sebastién Comerón said in a statement.
Related: What’s dark matter?
Dark matter is effectively invisible since it doesn’t interact with light just like the on a regular basis matter that composes stars, planets, and us. Its presence may be inferred by its gravitational interactions, nevertheless. The existence of this shadowy substance was first posited when astronomers observed massive galaxies rotating so fast they might fly apart if it weren’t for the gravitational influence of some unseen mass holding them together.
This fact resulted in scientists theorizing that each one large galaxies are wrapped in an envelope of dark matter, and this has grow to be a vital assumption in the event of theories of galactic evolution. But the invention of a galaxy that appears to haven no dark matter challenges that assumption.
Examining an anti-social relic galaxy
Considered a cosmic relic, NGC 1277 is unusual amongst galaxies since it has had little interaction with other surrounding galaxies. Galaxies like this are considered to be the stays of giant galaxies that existed within the early universe. As such, these relic galaxies are essential in helping astronomers to know how the primary galaxies formed.
To help on this line of inquiry, Comerón and colleagues observed the relic galaxy NGC 1277 with an instrument called an integral field spectrograph. This allowed them to map the motion of the galaxy and determine its mass and the way that mass is distributed.
This revealed that the distribution of NGC 1277’s total mass — which should include dark matter — was the identical because the distribution of the mass of its on a regular basis matter contents, in other words, stars, dust, gas and planets. That signifies that throughout the galaxy’s radius, there cannot be a dark matter content any greater than 5%, however the findings are more consistent with an entire absence of dark matter in NGC 1277.
That is surprising, because the currently favored models of cosmic evolution including the usual model of cosmology, suggest NGC 1277 needs to be comprised of between 10% and 70% dark matter.
“This discrepancy between the observations and what we might expect is a puzzle, and perhaps even a challenge for the usual model,” team member and University of La Laguna researcher Ignacio Trujillo said.
Where did relic galaxy’s dark matter go?
The scientists behind this revelation have a number of ideas about why NGC 1277 is so deficient in dark matter.
“One is that the gravitational interaction with the encompassing medium throughout the galaxy cluster through which this galaxy is situated has stripped out the dark matter,” team member and University of La Laguna researcher Anna Ferré-Mateu. “The opposite is that the dark matter was driven out of the system when the galaxy formed by the merging of protogalactic fragments, which gave rise to the relic galaxy.”
The team is not totally satisfied with either explanation and can, subsequently, proceed investigating NGC 1277 with the William Herschel Telescope (WHT) on the Roque de los Muchachos Observatory on the Canary Island of La Palma.
If these future investigations confirm this relic galaxy lacks the universe’s most mysterious type of matter, the scientists think this would possibly not challenge the existence of dark matter altogether. Conversely, the team believes it could challenge alternatives to dark matter models, so-called modified gravity theories.
“Although the dark matter in a particular galaxy may be lost, a modified law of gravity have to be universal; it cannot have exceptions,” said Trujillo. “So a galaxy without dark matter is a refutation of the sort of alternative to dark matter.”
Conclusive answers may have to attend, though, Comerón acknowledged. “The puzzle of how a large galaxy can form without dark matter stays a puzzle,” the scientist concluded.
The team’s research is published within the journal Astronomy and Astrophysics.