Astronomers Find a Galaxy Without Dark Matter for the First Time
30 March, 2018, 00:45 | Author: Lucy Floyd
The laws of motion and gravity tell us how fast these objects should turn given their bulk.
Working with the speeds at which these clusters of stars were moving, they were able to calculate the mass of DF2. It's coming in at around one two-hundredths the mass of our Milky Way. Based on these indirect observations, researchers have estimated that dark matter makes up about 27 percent of our universe.
However, this new study by astronomers using the NASA/ESA HubbleSpace Telescope and several other observatories of a galaxy known as NGC 1052-DF2 that appears to have very little, if no dark matter al all, now challenges this currently-accepted theory. And that normalcy is deeply weird.
The scientists spotted NGC1052-DF2 using the Dragonfly Telephoto Array, a telescope in New Mexico. "Dark matter has been rolled into galaxy formation and evolution theories for decades now, but this discovery of a galaxy that seems dark-matter-free puts a damper on many of those theories".
Unfortunately, dark matter research is facing a hurdle, as the Trump administration's NASA budget proposal for fiscal year 2019 places the funding of the Wide-Field Infrared Survey Telescope in question.
For a galaxy like NGC1052-DF2, you'd expect to see about one hundred times more dark matter than visible matter-but astronomers found it has nearly no dark matter.
In other words, finding a galaxy without dark matter is pretty good evidence that dark matter is a real thing.
Adding up the clusters' motions and NGC 1052-DF2's mass, they realized there might be no dark matter behind this particular galactic curtain. "This whole story is one of dark matter being the scaffolding on which every galaxy is built", said van Dokkum.
The universe's ordinary matter includes things like gas, stars, black holes and planets, not to mention shoes, umbrellas, platypuses and whatever else you might see on Earth. Given that there isn't a trace of the dark matter, data suggests that it's made entirely of normal matter. And over time, those clumps attracted the gas with their gravity. It may have been formed from gas interaction blowing out or into a larger galaxy. They do not know how it formed, but have some hypotheses, including the possibility that a cataclysm within NGC1052-DF2 swept away all its gas and dark matter or that a massive nearby galaxy played havoc with it.
While NGC 1052-DF2 doesn't break any fundamental rules of the dark matter theory, Bauer said the galaxy is surprising and unexpected enough to force astrophysicists to develop some new models of how galaxies come together. Sure, MOND doesn't easily explain a galaxy behaving as if there is no missing mass. Hubble helped them better identify the globular clusters and measure an accurate distance to the galaxy.
"I don't find that [point of view] at all compelling", Bauer said.
There are 200 billion observable galaxies, perhaps more, astronomers estimate.
The researchers describe the galaxy as looking like "a diffuse blob sprinkled with very compact star clusters". More recently, Verlinde suggested an alternative called "emergent gravity", in which gravity is a byproduct of quantum fluctuations and dark energy (another scarcely understood phenomenon, one that seems to be causing the universe's expansion to accelerate). "So, this is at the hairy edge of credible".
In the Milky Way there is about 30 times more dark matter than normal matter. What scientists know about it is that it's an elliptically shaped galaxy, which they have named NGC1052-DF2.
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Assange's internet access was also interrupted in 2016 after a WikiLeaks dump targeting Hillary Clinton's presidential campaign. Meanwhile, there's still an arrest warrant for him in Britain for jumping bail.
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