The uncertainty of science: Astronomers have strengthened their evidence that one particular nearby galaxy is completely devoid of dark matter, a situation that challenges the existing theories about dark matter which suggest it comprises the bulk of all matter in the universe.
The astronomers had made their first claim that this galaxy, NGC 1052-DF2, lacked dark matter back in 2018, a claim that was strongly disputed by others.
The claim however would only hold up if the galaxy’s distance from Earth was as far away as they then estimated, 65 million light years (not the 42 million light years estimated by others). If it were closer, as other scientists insisted, then NCC 1052-DF2 likely did have dark matter, and the theorists could sleep at night knowing that their theory about dark matter was right.
To test their claim, the astronomers used the Hubble Space Telescope to get a better, more tightly constrained estimate of the distance, and discovered the galaxy was even farther away then previously believed.
Team member Zili Shen, from Yale University, says that the new Hubble observations help them confirm that DF2 is not only farther from Earth than some astronomers suggest, but also slightly more distant than the team’s original estimates.
The new distance estimate is that DF2 is 72 million light-years as opposed to 42 million light-years, as reported by other independent teams. This places the galaxy farther than the original Hubble 2018 estimate of 65 light-years distance.
So, does this discovery invalidate the theories about dark matter? Yes and no. The theories now have to account for the existence of galaxies with no dark matter. Previously it was assumed that dark matter was to be found as blobs at the locations of all galaxies. Apparently it is not.
However, the lack of dark matter at this one galaxy does not prove that dark matter is not real. As noted by the lead astronomer in this research,
“In our 2018 paper, we suggested that if you have a galaxy without dark matter, and other similar galaxies seem to have it, that means that dark matter is actually real and it exists,” van Dokkum said. “It’s not a mirage.
Ah, the uncertainty of science. Isn’t it wonderful?
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