 In a galaxy far away, an incredible discovery has been made and it's not what's in the galaxy that's surprising to us, but what actually isn't in that galaxy. And this is your space pod for April 5th, 2018. I really like talking about dark matter. It's a fascinating subject to me and I really appreciate the enthusiasm the community of tomorrow has commenting on our space pods or our news stories about dark matter. And this space pod, yep, we're going to be talking about dark matter or specifically the lack thereof, which is making us scientists kind of scratch our heads. But we're not sweating about the lack of dark matter, we're actually relishing in it. I'm talking about this galaxy here, lovingly named NGC 1052-DF2. If it looks a bit anemic to be called a galaxy, you're not wrong. It's the same volume and overall size of the Milky Way, but has 200 times fewer stars. And those stars are all clumped together at very far distances apart from each other. So diffuse is this galaxy that those blobs behind it in this image from Hubble are other more distant galaxies. Now this galaxy has a lot to say about dark matter, but how do we detect something that doesn't emit electromagnetic radiation, also what we call light? This is something that's been asked in the comments of space pods about dark matter before, so let's dive a bit into our detection and how we view dark matter. We primarily use two techniques to determine where dark matter is. Gravitational lensing is one that we use. Dark matter imparts a gravitational force, which means it can bend light. And we can see that gravitational pull in the bending of light from distant objects like galaxies, especially light coming through large-scale galaxy clusters. And the bending is far beyond the mass of the visible matter. Now another way is that we look at how fast objects are moving inside of a galaxy, or how fast whole individual galaxies are moving in huge galaxy clusters. And we find that galaxies themselves and galaxies in clusters are moving too fast to account for just visible matter. The faster something moves, especially in large-scale structures, the more masses needed to keep it all together. Now many alternate theories have been hypothesized, such as modified Newtonian gravity, and they work at local levels, but scale them up to either macroscopic or scale them down to quantum levels and they completely fall apart. They're like Swiss cheese, they're delicious, but they're full of holes. And science isn't a fan of holes. Now Peter Van Dulkum, a professor of astronomy and physics at Yale, led a team that studied NGC 152-DF2. They observed this extremely diffused galaxy with the dragonfly telephoto array in New Mexico as a part of a survey to find diffused galaxies that astronomers may have missed. Eventually the Keck and Gemini telescopes in Hawaii and Hubble in orbit were also brought on board to have a look. Now researchers measured the speed of the clusters of the stars and they found that they were moving at an extremely slow pace. From this orbital velocity data they determined that the mass of the galaxy is startling to us. It contains little if any dark matter, roughly one four hundredth of what would be expected of a galaxy of similar size. Now you'll know earlier I said that science doesn't like holes, and you're probably thinking to yourself, hey Jared, I know you and the astronomical community at large think that dark matter actually does exist, but isn't this a pretty gaping hole? Well surprisingly it isn't. If anything it's a data point that strengthens the argument for the existence of dark matter. Honest to goodness the formation of this galaxy without dark matter is a massive mystery, and time has been granted on the Hubble Space Telescope to further assist the studies. Now some ideas include that it may have sprung from a cloud of gas that didn't have much dark matter around it, but how does a lack of dark matter actually solidify the argument for dark matter itself? Well those modified theories of gravity, when you apply them at galactic levels, they result in galaxies all behaving uniformly. But finding the galaxy with the behavior of NGC1052-DF2, which is completely out of line, doesn't add up. It violates the expected behaviors predicted under these modified theories of gravity. Finding a galaxy acting weirdly in a non-uniform universe is exactly what we would expect to see if there was some kind of mysterious force at play. Of course there be galaxies devoid of it, and this is the proof in the pudding. So for now dark matter lives to see the light of another day. Now if you like this space pod don't forget to tune in to orbit11.13, our previous episode where we talk about what exactly is holding humanity back from returning to the cosmos. And don't forget to like and subscribe to us. And also if you like this in our show you can help crowdfund the shows of tomorrow by heading on over to patreon.com slash tmro or makersupport.com slash tmro. So until the next space pod keep exploring.