Galaxy With No Dark Matter Baffles Astronomers
NGC1052–DF2 is 'weird'
By Newser Editors and Wire Services
Posted Mar 29, 2018 12:56 AM CDT
Updated Mar 29, 2018 2:00 AM CDT
This 2016 photo provided by Pieter van Dokkum shows the "Dragonfly" telescope in New Mexico. Using the assembly, van Dokkum and colleagues found a large, thin galaxy called NGC1052–DF2 in the northern constellation Cetus.   (Pieter van Dokkum via AP)
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(Newser) – It's a double cosmic conundrum: Lots of stuff that was already invisible has gone missing. Astronomers have found a distant galaxy where there is no dark matter. Dark matter is called "dark" because it can't be seen. It is the mysterious and invisible skeleton of the universe that scientists figure makes up about 27% of the cosmos. Scientists only know dark matter exists because they can observe how it pushes and pulls things they can see, like stars. It's supposed to be everywhere, reports the AP. But Yale University astronomer Pieter van Dokkum and colleagues spied a vast, old galaxy with relatively few stars where what you see truly is what you get. The galaxy's stars are speeding around with no apparent influence from dark matter, according to a study published in the journal Nature.

Van Dokkum says the galaxy, NGC1052-DF2 in the northern constellation Cetus, may have formed in the very early universe in a way astronomers don't understand yet. "There's nothing else, just the stars," he says. With measurements from telescopes, van Dokkum and colleagues calculated how fast its clusters of densely grouped stars moved. If there were a normal amount of dark matter those clusters would be speeding around at about 67,000mph. Instead, the clusters were moving at about 18,000mph. That's about how fast they would move if there were no dark matter at all, van Dokkum says. The team also calculated the total mass of the galaxy and found the stars account for everything, with little or no room left for dark matter. Case Western Reserve astronomer Stacy McGaugh's take: "This is a weird galaxy." The AP has much more here.

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