Dragonfly Telephoto Array (Canon 400mm array) + ultra-diffuse galaxies

9:18you're going to get image distortion that way, right? But what these guys did was a bunch of small lenses put together. Now what is the advantage? Now the advantage is for mirrors, right? If you have a mirror lens, which is what modern telescopes all use, they all use mirrors. The light has to come down and then has to get sent back up because it's a mirror. So it's going to bounce up and there's a secondary mirror that then bounces the light back to a detector. Usually it's like warranted in some way or something. But at the end of the day, you need a secondary mirror. >> And that mirror needs to be held up by some kind of scaffolding. In the James Web Space Telescope, it's hexagonal scaffolding. In the Hubble Space Telescope, it's diamond shaped

10:00scaffolding like in a square 90°. Which is why when we see the images that these telescopes produce, >> the mirror structure or the architecture actually dictates. For example, I remember when uh James Webb first came out, certain objects had a certain star pattern or or like a certain visual representation that little like little Yes. that was different than Hubble, which is because of this diagonal versus hexagonal structure. >> Yeah. And those are called diffraction spikes. It it happens because of scattered light from that scaffolding. >> Yes. Well, if you want to image really really diffuse things, that becomes a really big problem.

10:40>> When when you say diffuse, what do you mean? >> Diffuse by really dim. >> Okay. Really? >> Like not a lot of light. Got it. >> As in like so little light that we're pushing the sensitivity of the CCD, the actual um charge couple device, the thing that is collecting the light and turning it into an electrical signal. Right? There's a bunch of silicon at the end of your detector. That's what makes up a charged couple device. And when the photon hits that silicon, it releases an electron and then you're like, "Oh, I got a little photon from there." Right? >> If you're if you're imaging really diffused things, even that the scaffolding, the scattering from that scaffolding is going to be a problem. So that's why you want to use lenses, but

11:22you can't use big lenses because of the aberration, like the deformation problem. So what if these guys just figured from the dragonfly telephoto array, what if we just use a bunch, right? like we used like 20 or 30 small lenses >> and the compile >> and we compiled them together. Okay. And it's it it was like relatively cheap I can imagine, right? Because >> you're not like making custommade lenses. This is just Canon 400 mm f2.8 that you put together. >> Calling up Carl Zeiss. We need a custom giant 13 meter. >> And he's like, uh, how about $10 million? Like, no. So, so this was this was a really cool thing. And in 2015, they came out with these extreme ultra

12:04diffuse galaxies. Dragonfly 44 is an example. >> This is a galaxy. You can see the faint fuzz in the middle. >> Yes. >> Not a lot of stars. Yes. >> And from what we can tell from how these things are moving around when you do spectroscopy and you figure out the Doppler shift. So you figure out how much is the red shift in this direction, the blue shift in this direction. From there, we can figure out how fast these things are moving around. >> Yep. And then you back calculate how big does the galaxy have to be? It's like dark matter dominated. 90% of it is dark matter. 95% of it is dark matter. So it's this ultra diffuse galaxy that seems to have a lot of dark matter. Okay. It's been hard to catch before because usually with normal telescopes,

12:45the scattering takes that away. But now with this new dragonfly telephoto, we can start imaging really diffuse structures. >> That that makes it. So the the point is with the normal structure uh we need bright objects for it to work well. >> Mhm. >> Um and these sort of dark matter galaxies where it's predominantly this this thing we don't understand as that does not interact with light. It becomes very difficult to see it or to to image it I should say. >> Yeah. To image it. >> To image it. >> But with this lensbased architecture it lowers it increases the >> signal to noise. >> Yes. such that we can at least get >> something >> something. Yeah, exactly. And then this

13:26particular paper is candidate dark galaxy 2. It is taking these ultra diffuse galaxies to a whole new level. >> It's pushing that diffuse into now dark because now we're getting 99.9% >> dark matter.