Small galaxies without dark matter already caused a stir a few years ago. But now evidence has even been found for the first time that there is also a very large galaxy without dark matter. And that doesn’t fit the standard model of cosmology at all.
This is the galaxy NGC 1277. It is a spiral galaxy located about 220 million light-years from Earth. In 2018, it was discovered that no new stars are forming, but the system consists only of old stars, which formed billions of years ago. It is a so-called relic galaxy, which means that it has had no interaction with other galaxies. It is probably the remnant of a gigantic galaxy that originated in the early universe.
No dark matter
Researchers from the IAC Astrophysical Research Institute of the Canary Islands and the University of La Laguna to have now discovered that NGC 1277 contains no dark matter. This is the first time that in such a large galaxy – the mass is many times that of our Milky Way – no evidence has been found for this now well-known but invisible part of the universe. “This does not correspond to current cosmological models that assume the existence of dark matter,” explains lead researcher Sebastién Comerón.
According to the Standard Model, very large galaxies contain substantial amounts of dark matter. This dark matter is basically invisible. We can observe it due to the strong gravitational pull that matter exerts on nearby stars and gas.
This material was not found in the ancient galaxy NGC 1277. “The reason we decided to study NGC 1277 with a spectrograph is that it helps us understand how the first galaxies formed,” says Comerón. This allowed the researchers to measure the movement of stars up to 20,000 light-years outside the galaxy and deduce that there could be no more than 5% dark matter in the observed radius and probably no dark matter at all.
This runs counter to current models. They assume that a galaxy the size of NGC 1277 should be composed of at least 10% dark matter with a maximum of 70%. “The discrepancy between the observations and what we expected is a puzzle, and perhaps even a challenge for the Standard Model,” said researcher Ignacio Trujillo.
Two unsatisfactory explanations
Is there no possible explanation for the lack of dark matter? Yes, yes, the article even mentions two. “One possibility is that due to the interaction of gravity with the surrounding intergalactic medium, dark matter disappeared,” says researcher Anna Ferré-Mateu. “The other explanation is that dark matter was kicked out of the system when NGC 1277 formed from protogalaxies a long time ago.”
But for the authors, the two explanations are not satisfactory “so the puzzle of how a huge galaxy can form without dark matter remains a puzzle for now”, explains Comerón, who continues to investigate the mystery with his team.
If NGC 1277 does not contain dark matter, this does not confirm the alternative models which say, for example, that dark matter does not exist at all. “While dark matter may be lost in a specific galaxy, a modified law of gravity must be universal. There can be no exceptions, so a galaxy without dark matter is a refutation of these kinds of dark matter alternatives.
Earlier we wrote about how Hubble confirmed two years ago that there are galaxies without dark matter. The telescope then leaned on the galaxy NGC 1052-DF2, but it is not the only one. For example, researchers said in 2018 that the galaxy NGC 1052-DF4 had almost no dark matter. And other researchers have discovered nineteen other dwarf galaxies in 2020 that appear to contain virtually no dark matter. However, they were all relatively small galaxies, so now one has also been found which is mega in size.
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