10:12Astronomers Discover Dark-Matter Deficient Galaxy for 1st Time

Greg Lawrence
March 30, 2018

In a first, scientists have discovered a galaxy that is nearly completely devoid of dark matter - the mysterious substance believed to make up most of the universe.The galaxy, known as NGC1052-DF2, has been classified as an an ultra-diffuse galaxy, a relatively new type of galaxy that was first discovered in 2015. However, the discovery has led to more questions than answers, and further research into how a galaxy might form in the absence of dark matter will need to be undertaken before it is fully understood. It's paradoxical, but the galaxy lacking dark matter could teach us a lot about dark matter itself.

Dark matter's existence is inferred from the motion of objects affected by its gravitational pull.

"There are simulations of the universe starting back near the Big Bang that show dark matter was produced and actually gravitationally attracted normal matter to it, and that's how the galaxies were formed", said Dan Bauer, a physicist at Fermi National Accelerator Laboratory, who studies dark matter and did not work on the paper. "So, finding a galaxy without it is unexpected".

Dark matter is still a great mystery for astronomers and scientists.

The clusters, they found, travelled at the same speed as the galaxy, itself moving through the Universe. In fact, every galaxy that astronomers have ever studied contains dark matter. Now researchers are pondering possible explanations for this missing dark matter in NGC 1052-DF2.

The scientists apparently expect the kind of inquiries that will certainly be presented by individuals that see this and also ask yourself why we require any kind of dark issue around anyhow (a populace that consists of a variety of routine Ars visitors).

Indeed, over the last few years Dokkum and Abraham have used it to uncover a whole new category of sparsely populated "ultra diffuse galaxies" - and sparked a cottage industry as astronomers struggle to explain their odd properties.

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"I spent an hour just staring at the Hubble image", said van Dokkum, the Nasa website reports.

There are 200 billion observable galaxies, perhaps more, astronomers estimate. Or would the current appearance of the galaxy be the result of a cataclysmic event within it?

Van Dokkum and colleagues identified the galaxy, NGC 1052-DF2, using a low-budget setup called the Dragonfly Telephoto Array in New Mexico, which they designed from 48 commercial cameras and paparazzi-style lenses. If it has no dark matter, how did it even evolve into a galaxy?

"There is no theory that predicts these types of galaxies - how you actually go about forming one of these things is completely unknown", added co-author Allison Merritt from Yale University and the Max Planck Institute for Astronomy, Germany. Previously, the team took a look at other galaxies with similar properties and the same class as NGC-1052-DF2, discovering that they nearly entirely consisted of dark matter. Nobody knows exactly what it is, but scientists believe that it is out there because in can be observed when galaxies and stars move.

"It challenges the standard ideas of how we think galaxies work", said Dokkum. Using these velocities, they calculated the galaxy's mass and determined that the visible stars, gas and dust in DF2 accounted for most of the mass and that there was only 1/400th the amount of dark matter expected. The galaxy is a complete mystery, as everything about it is odd.

About a year ago, University of Waterloo researchers captured a composite image that strongly supports the existence of dark matter.

Case Western Reserve astronomer Stacy McGaugh confirmed that the findings make no sense, but, well, there they are anyway.

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