JWST lensing and “gravity bifocals”

23:51>> And behind this cluster of galaxies are a bunch of other galaxies whose light is being distorted by the gravitational field of this foreground uh galaxy cluster. >> Okay. >> So, this galaxy cluster is billions of light years away and the sources behind it are another few billion light I mean, so these are, you know, we're looking across most of the observable universe. >> So, the idea is like if we're if we're here at this point right in front of my face, a billion light years away is one dot on this image. And then right behind it in our line of sight, another billion light years away is another dot of a light source. Again, from a line of sight perspective

24:31that comes directly into our instrument. >> That's right. But because you have this gigantic concentration of material in between us and the light source, >> Mhm. >> we see those distant sources magnified and distorted. So, if we if we zoom in now, >> Yes. >> uh right. So, this is a zoomed-in uh part of that wider image. >> Yes. >> And you see in the top center there is this bright uh yellow object. >> Yes. >> That's a regular galaxy >> Okay. >> in the cluster. >> Mhm. >> And the yellow the other yellow banana that you see kind of draped on top, >> Yes. >> that is a background galaxy that is being warped and distorted. It's not Sorry. It's not actually being warped

25:12and distorted, but our image of it, what we see, is a warped and distorted image of that source. >> So, what we're saying is for those who are listening on audio, we always encourage uh because we do so many visuals on the show. Um but many of you have probably seen these JWST images. We sort of see a diffuse circular object, which is our galaxy that's closer to us in this 1 2 3 line of sight point explanation we did earlier. And then the kind of the yellow orangeish banana, are we saying that it is for the most part a similar diffuse circular galaxy cluster, but on its way to us, the light on its way to us is

25:54being is is being manipulated by all the gravitational and other things going on, so it comes a little It looks funky to us in the image, but that's not literally what it looks like in real life. >> Yeah, it's probably a boring-looking, you know, regular galaxy. Maybe it's interesting. Maybe you Maybe it's a spiral galaxy or something pretty, right? >> Sure. >> we see is this, you know, warped banana-type structure. >> Yes. >> And that's a purely optical effect caused by the deflection of light by gravity, in this case by this bright cluster member that has enough stars in it that we can see. >> Makes sense. >> So, that's This is gravitational lensing. And by the way, you see lots of other cool bananas in this image. That's

26:36not the only one. >> So, so when we when you say gravitational lensing, right? What you mean is the um the optical distortion that arises when we use our telescopes to look deep into the universe and there is the foreground the foreground point light source is impacting our ability to observe the background point light source on its journey to our devices. >> Yeah, so there is some lens, in this case it's gravity, that is

27:17distorting the image of some background source. >> Oh, so you like you're literally using lens in the way like it's almost like like glasses. Like we're putting on bifocals and it's distorting the light on its way in. >> Right, gravity bifocals. >> Gravity bifocals. >> So that's the idea. And so we can use that effect to study all forms of matter, regular matter and dark matter because they both have gravity. >> Oh, that's a good point. >> We'll come back later, you know, one of the challenge we'll come back to that point later. One of the challenges is disentangling the contribution of dark matter to this lensing effect from the contribution of regular matter to this lensing effect. >> Cuz they all interact with gravity and got it. Okay. >> So I I propose we we circle back to

27:59that. Let me tell you more exactly about what we what we actually do with these lenses cuz it turns out that some lenses are better than others for some gravitational lenses are better than others for this. And the particular kind of lensing system that we study are called strong gravitational lenses. >> Okay. >> As opposed to weak gravitational. >> So this is the strong ones. >> So if in my silly glasses or contacts analogy, if you if you're a negative 0.5 or negative 1, that's weak lensing. If you're a negative 4 or negative 5 like I am, strong lensing. >> Yeah, yeah. If you can't see your hand, then you need strong lensing. So let's to introduce let's let's introduce

28:40strong lensing. So let's look at the fish, number five. All right, so this was a a movie. Uh I believe Yashar Hetzave is was the