Missing Dark Matter: The Mystery of the 19 Galaxies

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Astrophysicists Scramble To Figure Out The Absence of Dark Matter In Nineteen Newly-Discovered Dwarf Galaxies.

Studying dark matter is a tricky business. Those familiar with astronomy and the techniques used to determine what we know can tell you that there’s a lot of math and a lot of logical inference involved. In dark matter’s case, its very nature makes it nearly impossible to observe. It doesn’t reflect or emit light, so direct observation is out of the question for now. However, we know it has to be there because if it weren’t for dark matter, there wouldn’t be enough “normal” matter to form galaxies. In other words, the math of mass makes galaxies impossible without the existence of matter we can’t see.

Apart from the math, however, we can see its effects as its gravity bends the light around it. We observe this with “normal” matter all of the time, and it’s a cornerstone of Einsteinian physics. 

If you want to know more about dark matter, check out this video:

But Some Galaxies Don’t Seem To Have Any Dark Matter…

…and that’s got astrophysicists confused. Specifically, researchers are looking at nineteen recently discovered dwarf galaxies. If you missed it in the video, scientists use math to infer that dark matter has to exist in order for galaxies to exist. That’s because they swirl at rates that are different than they would be if the observable matter was the only matter in them.  These nineteen galaxies, though, swirl as if they are made entirely of “normal” matter. Additionally, the light-bending halos that help us observe dark matter obliquely are missing from these galaxies. 

Why Dark Matter… Well… Matters 

Please forgive the pun. Apart from literary tomfoolery, though, the existence of these and previously discovered dark-matter-free galaxies carries serious implications for current cosmological models. In a nutshell, there are two competing theories at the moment that explain the formation of galaxies and the universe. In one model—the Lamda cold dark matter model (ΛCDM)—the existence of dark matter is an essential component. Another model, however, the Modified Newtonian Dynamics model (MOND), rejects the name dark matter and suggests new models of gravitational physics are needed to explain the substances that must be there. 

One might be tempted to think, and indeed some have even argued outright, that the absence of dark matter in these dwarf galaxies is a validation of the MOND model. However, University of Helsinki astrophysicist Till Sawala points out that even if we tweaked our understanding of gravitational physics, MOND predicts that what other theories call dark matter should still be everywhere in the universe. So if one theory is wrong, so is the other. The only way to solve this mystery is to dig in using different tools and methodologies.

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Brandon Humphreys

Brandon Humphreys

I'm a wizard. I write stuff and it goes from my head into yours - Magic! Apart from that, I am the Senior Editor for Space Porn, a veteran, a rock guitarist, and a teacher.

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