Can Axions Be Dark Matter?

it's the age-old question what is dark matter like is it some kind of particle that doesn't interact with regular matter except for gravity is it that we just don't understand gravity at the largest scales if it is a particle what kind of particle is it and astronomers have proposed a lot of different kinds of particles very massive particles very light particles and there's one class of particles called axions that have sort of more Behavior like light but also matter and astronomers have been looking for evidence for this so my guest today is Dr amruth Alfred who is a PhD student at the University of Hong Kong actually he just got his Doctorate so I guess post doc at University of Hong Kong we talk about the observations that he studied in a gravitational lens that hints that maybe the Axion is the right explanation for dark matter and then we also just talk a lot about gravitational lenses because I am so fascinated by these and how they work as natural telescope lenses you've given me a lot of questions and I was able to pass a lot of those questions along to arm with so enjoy this interview with Dr ahm Ruth Alfred and I gotta say that is the coolest recording setup I have ever had talking to an astrophysicist this is the like this is the first time someone comes prepared with a condenser microphone uh a you know nice set of headsets uh this is this is the best I'm I'm really thank you thank you okay I know you know I I do some streaming on my own time so uh I had to upgrade you know slowly get the decent equipment at least yeah yeah I think that's my new rule I'm only going to talk to scientists who are also video game streamers right probably raises the bar yeah yeah yeah I mean you know you're gonna get good audio and video exactly you've already gone through all of the hassle of getting your setup done and then we can talk about the science so that's it uh you have no more of the people always give me a hard time they're like oh the audio quality of your guess is so mediocre I'm like oh I like but they were so interesting but um all right so let's talk about gravitational lenses so let's start with the big the big news and the reason that I that I reached out so you put you and your team put out a paper um picked up by some pretty big places um what did you what was the I guess the discovery that you are proposing in your paper well so conventionally dark matter people treat it as you know it's made of uh massive particles and that's sort of the standard Paradigm and then there's this alternative model called wave dark matter which where the dark matter is just made of very light particles that's really the main difference and then you know there's a lot of other models because the standard Paradigm ran into a couple of issues uh both in particle physics and astrophysics right there's been Decades of searches and really billions of dollars of funding looking for these massive particles people call them wimps for weekly interacting massive particles and we haven't really found any so there's there's a lot of motivation to consider other ideas and and so sorry just to interrupt so like this what is the difference I mean like I mean I think we can kind of wrap our heads around the idea of a bunch of particles that are not interacting with regular matter I mean that's already pretty hard but what is this idea of like wave based dark matter right right well it's just because the particle is so light right and then uh I'm sure you've heard about you know wave particle duality right everything you know everything is actually wave as well or a particle um and then this wave Behavior becomes stronger the lighter you get so very light particles are gonna have very large wavelengths we call this the debris wavelength after Louis de brois and um so because these wave you know the candidate particle for wave dark matter is so light there are ultra light particles their wavelength is so large that on astrophysical scales they kind of behave like waves they exhibit wave-like properties kind of like you know interference patterns and stuff like that like waves on a beach so theoretically you could you could throw streams of Dark Matter particles and they would interfere through interference patterns like photons right right yeah you know so on large scales like galaxies and Galaxy clusters they it's kind of like ripples in a pond they have these they interact with each other they have these interference patterns and then you know every interference pattern whenever that happens there's constructive destructive interference right right um so you get all these funky Behavior which you wouldn't get with the massive particles they just wouldn't show this kind of thing but to all other purposes it still behaves the same as the prep you know the you know that it is cold that it doesn't you know it has a small cross-section doesn't interact with itself or regular matter right through anything but gravity yeah no that's uh so that's important and uh you know there's still people who work on hot Dark Matter warm Dark Matter the right the three classes and uh it's just that astrophysical observations prefer Dark Matter to be cold it's not to say that all of it's cold you know some of it might be warm some and even less hot maybe uh but you know looking at the large-scale structure of the universe and then you compare it with simulations what it tells you is that probably Dark Matter needs to be cold and slowly moving and then so you know wave dark matter and then massive particle dark matter they're they're still cold this is important you need to you know there's like primary astrophysical observations that you need to reproduce if you wanna consider that model you know seriously um and the two of these main ones there's there's a couple but the two main ones are you need to be able to reproduce the large-scale structure of the universe right so that all the structure we see that the cosmic web uh the second is you need to be able to reproduce the cosmic microwave background the CMB and then those two you know you need in any kind of cosmological model uh and then wave dark matter as well as the you know standard dark matter um they both do this right okay okay and so what is the observation then that you were making uh well we you know we didn't actually um make the observations ourselves we used data from from a previous team that did it from previous work um so this has never been done before really where people test Dark Matter models with gravitational lensing when it comes to um lensing of quasars quasars are just distant bright galaxies right and um historically for almost two decades now astronomy and lensing has had this problem called lensing anomalies where when you look at lensed images of very distant galaxies or quasars and then you try to reproduce the brightnesses of those images you what we find is that standard Dark Matter models can't reproduce these brightnesses more often than not interesting so so in this case like you've got a Galaxy cluster foreground and then you've got some Quasar in the background of the Galaxy clusters is acting as a lens for the Quasar right oh you actually have a Galaxy as the lens typically okay okay Galaxy is a lens yeah yeah and and and so the brightness that you're getting of this lensed Quasar doesn't match up with what the predictions should be right right and is that because it's like there's there you need more mass in the lensed Galaxy or less Mass we we don't know uh you can't yeah uh you can't tell like it doesn't tell you um and then people have tried uh invoking different explanations to you know try and circumvent this problem and then they've kept uh running into a wall where none of these explanations seem to you know sometimes these explanations help resolve the problem but more often than not they don't it's dust obviously but what yeah sure it does it always does like that's always right yeah nice you know dustful stuff yeah um you know people people try adding in these um sub Halos which are sort of like mini galaxies and then the standard cold Dark Matter Paradigm predicts these kinds of invisible galaxies well invisible um Halos of dark matter is just I don't know why people use the word halos in in the field um you know a Halos tip if you told a stranger Halo it's like a ring on your head right like angels have Halos but when astronomers use Halo it's it's just a spherical cloud of of dark matter so they say dark matter Halo it's just you know a blob of dark matter it's very misleading um you know I hope people listening I'm saying this because people listening are like why is there a ring of dark matter but then it's just a it's a cloud a spherical Cloud um and then yeah the standard Theory simulations predict many of these smaller Halos sort of like baby Halos around the parent Halo uh and you know we don't see these in observations um it's one of the problems called The Missing satellite problem which is one of the things that plagues the standard Paradigm uh you know around our Milky Way Around our galaxy simulations predict about more than hundreds of satellite galaxies where we only see a few tens um so there is a large discrepancy there and people try to use these baby Halos sub-halos to see whether that could help resolve these lensing anomalies and sometimes it can but then in sometimes it can't um yeah and I know it is tricky because in some cases if you do have like a baby Halo and it has primarily dark matter and no stars it's really hard to see it yeah um yeah and I don't know if you saw uh some Chinese scientists it found a uh Dark Matter satellite galaxy to the Milky Way a couple months ago um relatively close so they're out there they do exist right right but yeah but not at the quantity that you would be expecting yeah yeah yeah and you know I you know I'll probably get a lot of flack for this from the uh the standard cold Dark Matter people but yeah they're not listening don't worry about it yeah okay they're not going to be listening right it's the cool people listening yeah yeah um no you know because it is a topic of debate I'm not saying that you know it's guaranteed 100 but it's definitely a topic of strong debate and especially in the past it was much more severe but um nowadays you know some people say that okay it's not really a problem it's just that our simulations suck uh and then if we have better simulations then this isn't really a problem and sure it might be the case uh but it's it's just definitely a topic of hot debate um you know because there's other issues as well uh apart from this missing satellite thing so you looked at these lens quasars and and what were you hoping to see well so you know I didn't tell you this but all this time people were finding brightness anomalies because you couldn't reproduce the brightnesses but more recent observations which um with much higher resolution with radio telescopes um you know it's called vlbi very long Baseline interferometry um and you use these you know they're the resolution you get is orders of magnitudes higher than the Hubble Space Telescope which is you know like the holy grail for astronomers well now the jwsd and infrared um and then what what we found is you know there's these brightness and position anomaly that what people found um and then we were like you know look uh wave Dark Matter it has this wave-like Behavior right and then one of the defining characteristics is that it produces this kind of um interference pattern which leaves behind a lot of uh structure in the mass so it's not like smoothly distributed but there's a lot of blobs of mass um that are more dense and less dense than the average density so you might want to picture it like I don't know when waves crash crash on the beach like the froth uh that forms you know um it's sort of like that it's like very a lot of structure going on and then this is a very unique prediction you can't it's not the same thing as adding in these baby Halos because the baby Halos are just adding in Mass right but this wave dark matter you know it's gonna have negative uh fluctuations as well and so is this like structure in the like the Galaxy itself because of the effect of the dark matter or is this purely something that you're seeing in the lens like is this is it right structure actually there around the Galaxy yeah so the first time you know we filmed this out was in 2014 uh that was the first time that's full simulations of wave Dark Matter were done also by one of our collaborators and turns out every Galaxy um has this kind of structure it has this wave-like Behavior you know taking over and this kind of interference pattern leaving behind this Rich very rich structure and then it happens in Galaxy clusters as well so basically every dark matter Halo right okay and so when you look at a gravitational lens where is this I mean I think about things like for example astronomers were able to see exoplanets around other stars just by using gravitational microlensing yeah it's such a sensitive technique yeah yeah and is that is that sort of what's doing the heavy lifting here is the is the lens itself um well yeah the you know the lens is what's important here definitely you know because what happens to the lensed images lets us probe what's going on in the lens and that's why we can infer something about the Dark Matter distribution in this case it's not micro lensing because it's strongly lensed images so it's strong lensing so you you know you especially in the radio you even see resolved images so you don't just see blobs but the the particular object we're looking at it's um it's a very it's you know it's an interesting object it's it's a quasar so it has a central core of the of the Galaxy which is imaged only in Optical with the Hubble Space Telescope but then it has two radio Jets on either side kind of you know going out out of the out of the center and then that's imaged only in radio and then this jet you know it has it has a lot of structure it's actually incredible when you see it because there's only a handful of these radio lenses you know you could literally count them on like one hand um so it's very rare people it's it's very rare so that's something we try to emphasize in our work uh we're like look you need if you if you can get radio Imaging of lenses you're going to be able to do incredible stuff with it um so this yeah this thing is really really interesting you know a central core and then a radio jet coming out of it and then all of those provide very rich constraints um that you could never really do before in lens modeling and so if this is true and what you're seeing is is correct what are the implications for cosmology well you know it this is this what what this would tell us is that probably it's time to take um you know the candidate particle for wave dark matter is called axions that's just the uh the technical term you know fun fact this people you know most people don't know why it's called axions do you know why it's called axions no I don't Axion yeah well so the person who proposed this uh was Frank will check so he's the Nobel Prize Laureate in 2006. um and then the Axion it wasn't just proposed as a candidate for Dark Matter it was proposed for solving other problems in physics uh in theoretical physics as well and then um he said look it uh cleans up a few problems in physics and then he was in his kitchen and then there's this detergent called Axion I don't know if you've ever seen it it's like a cleaning detergent it's it's a company yeah right and then he saw it and said look I'm just gonna name it Axion so that's where that's where the name comes from that's amazing this is Sir you know sometimes they have uh questionable names but sometimes they're they're pretty funny I think it's better than a acronym so I think it's all right you know um so right and so like a lot of the people who are watching this are listening to this they're familiar with the term Axion but but essentially what you're saying is is that of all of the proposed explanations for dark matter if you are seeing these these structures in the in the lens are correct then the Axion is the most likely candidate for dark matter right or something like it um some you know or or something like that that's what this particular um these anomalies tell us and that that's something you know it's very interesting because you could never really do that before um but so we're very careful to you know say that um lens models can always be more perfect like they can be they can always be better we're not really capturing the lens you know realistically you know because we're limited by the models we have and what how best we can represent a Galaxy so there are still some additional work that needs to be done which is what we're hoping to do in research um in some of the research that we have planned you know we want to take we want to try to capture the Galaxy as as best as possible in simulations um but you know assuming all of that wouldn't make a big difference then if axions were the true particle you know for Dark Matter then that's going to have cosmological implications as well because there's a lot of variation there's a lot of different predictions that wave Dark Matter axionic Dark Matter would do as as opposed to um massive particle Dark Matter so for people who who I mean they're familiar with the name what is the underlying astrophysical process that's believed to create axions um the the astrophysical process or the particle physics how do you get axions what yeah so there's multiple um hypotheses I shouldn't use the word theories there's multiple hypotheses in on how they're formed uh and then you know there's the axions actually span a wide range of mass uh and then what we're looking at is ultralight axions but there's also axions that are that are more heavy much more heavier like orders of magnitude heavier and they they all have different purposes in particle physics um and then there's there's a lot of processes like symmetry breaking and physics and the particular Axion that we're looking at it's postulated in string theory and I don't like using the word String Theory because it's not a theory I don't know what why people use that string hypothesis yeah it should be you know if you're doing science you wouldn't call it a theory I think um so yeah so you know it's predicted through all these a variety of mechanisms um there's a whole host of them and you know to be honest with you I I couldn't tell you the details yeah yeah it's it gets incredibly complicated and I couldn't tell you the uh the details on how that works but there are I mean I know there are people attempting to detect them directly there's even like an Axion detector setup at certain right right right yeah there's um direct detection experiments the same as how people were looking for wimps uh but the searches started a bit late but um I think you know some of the earliest searches were in the late 90s as well um but they're such a large parameter space to be explored um that you know because wimps have had now a lot lots of decades to be searched for and probably presumably you'd think maybe axions would need you'd need some time to to explore out the parameter space but there you know there there is there are direct detection experiments I actually went to this conference in Santander in Spain last week where people were it was just about Dark Matter there were still tons of people you know doing a planning projects and uh looking you know direct detection experiments or even in direct detection experiments um there's a lot of people working on stuff like that maybe not on axions most of the people were looking still for wimps or heavier particles but there were there were a few um so it's still not you know that popular so we we got a lot of pushback when we actually sent this paper uh and we sent this paper in so it the Paradigm still has a strong grasp on most scientists I guess has the the pushback helped you strengthen your position um well you know what myself it gives you pause right like you get all these people going like yeah you're wrong yeah and you say Explain how and then they do and then you go hmm am I wrong yeah right no that that's that's a good question because that's what science is all about right uh you wanna you know check out all the questions um and then unfortunately a lot of the pushback we got was not really um on the signs we did um you know for example uh when we had to send this paper in and through the referee process it was it was it was very painful because from one of the referees most of the comments we got were on the introduction of the paper so it wasn't on the science or the methodology or the results um he you know some they just had issues with uh how we were phrasing things in the introduction but that was you know what you do in an introduction of the paper is just a literature review right you don't actually say other things so there it's just people are willing to um they're not they're not willing to accept that the current Paradigm has problems that can't be easily resolved sure you know you can pull in a lot of Magic ingredients if you want but there's problems that you know I'm not saying that wave dark matter is Right a massive particle dark matter is wrong right because you can never say that and when we emphasize that in the paper as well but a lot of the pushback is kind of because people have locked in they've kind of put all their money into that idea and they don't want to consider the the alternative idea so whenever we get you know sometimes we get questions from people um about our paper and what the issues could be and then there's good questions like that like you know we need to do more analysis um in the future like a better modeling of the Galaxy stuff like that sure you know that's part of science but a lot of the pushback yeah it's it's it's quite sad to see why are these radio lenses so rare I mean I know that there are dozens of Einstein rings and other really great gravitational lenses seen by Hubble why are the radio equivalents so hard to find well they're so hard to find because we don't really know where to look like you'd have to first know that um the lensed quaser you're looking at has jets in the radio um which which you wouldn't know beforehand um and Well Radio observations are expensive I guess um you need to do you know lots lots of it and it's difficult to do you know when I started research I started off with um as an undergrad I started off um handling data from the vla the very large array uh and then radio oh my God dealing with Radio Data is um it's crazy uh I don't know if you you know have some experience you've heard someone talk about it it's it's incredible the amount I have yeah I mean my perception as you know as an outsider someone reporting on this is that in the beginning even like when I started as a journalist like you would see pictures from the Hubble Space Telescope and there were these beautiful wide field views of the sky you would see stuff from and like a telescope you can point it at the sky take a picture and now you've got uh you know a gigapixel image that you can look for things that are interesting in there but what the radio telescope you've got this tiny you've got like four pixels 10 pixels 100 pixels at the most that you're scanning across the sky uh you know degree not even degree Arc second by Arc second and you're slowly building and it's only been recently like when you think about some of the telescopes like meerkat you're seeing larger structures because the thing can just gather more pixels of the sky at the same time and now suddenly you're seeing these incredible um uh filament structures at the center of the Milky Way and and it gives you this Glimpse that radio telescopes are about to start taking pictures of the sky that are that look like photographs in the way that Hubble and jwstein all these do because they finally can gather a wide enough field of view which is really tricky right because it really tells you you just pointed one little point in this guy you go you know strength of the signal okay move over is there a signal here okay move over right like it's just it's a totally different world and so I can see how how finding these things there isn't going to be a Vera Ruben of radio telescopes for a long time yeah the next exciting one is the square kilometer array yeah that would be the big one that's going to start finding you know thousands of lenses you think um but yeah just the Precision with you know the resolution that that you can reach with um interferometric techniques that's the the key part and then radio lets you do that in radio when you use interferometry yeah the resolution that you can get is just incredible you just can't get it with the non-inter forums so what if you turned the Event Horizon telescope on this lens I have no idea you know that the resolution of I think the The Event Horizon telescope is uh you know orders of magnitude even better than what you could do with the uh than what has been done I don't know you you'd start seeing crazy stuff probably yes it's like yes yeah yeah yeah yes but do you think like do you think unless there's like make a prediction right like if you if you convinced and obviously you know after this interview goes live and the steering committee of the Event Horizon telescope now that they've imaged all of the black holes that they can need something else to use this collaboration for and they're gonna be like okay fine right wants this let's do it yeah uh what would you be what would you predict that you would see in the Quasar lens if if the wave uh dark matter is is more likely right uh well barring you know any technical difficulties I I don't know whether it be engineers at the Event Horizon would be like no no no way um you know I I don't know about that part but if yeah if we could get an image you would you would be seeing really any you know astrophysical object Nev you know it's never been it would have never been done before in history it would be an unprecedented level of resolution you would you'd manage to resolve structures you know in the radiojet to such a fine position and if if you know wave Dark Matter was what um the Galaxy was made of the lensing Galaxy um these images would have variations uh both in brightness and position and the kind of variations you would see it would be determined by the wavelength of the particle so it wouldn't just be you know you can constrain the mass of the Axion uh with these things which we can also do kind of uh it's just not you know within an order of magnitude with a few orders of magnitude but what you could do here is yeah you'd be seeing effects that you know hell we haven't maybe we haven't even predicted it because we don't we don't do simulations for sources that small because you just never would be able to see it in the observation but a but an astrophysical jet coming from a quasar fits the bill I mean like it gets more and more Point sources you get closer and closer to the source of the jet and to to image a gravitational lens you're already getting the benefit of however many orders of magnitude from the magnification of the foreground Galaxy that'd be Bonkers yeah I mean that would be amazing that would be amazing you'd be seeing a whole host of new things you know the apart from all these really odd things happening to the to the lens images uh who knows what you know you might be seeing some new phenomenon as well um these image the images would be jiggling about you know they'd be shifting in position and brightness um and then you'd be able to really capture all of these and wow The Lens model that you could make with that kind of data you could you could you could rule out a lot of stuff with that that kind of data yeah and I guess that's the question right it's like if you don't see anything interesting right then you'd be able to rule out the wave Dark Matter yeah and that would be awesome too because you know that's one of the good things that we're proud of when we were doing research and we're happy of um it's it's very falsifiable uh because well you know nowadays there's a lot of models going about in all of science really but there's a ton of free parameters and then you tune the knobs and then you fit the data uh and I don't know if you call that science I don't right but if you were able to wipe out an entire field of research with one observation you'd be okay would you be able to sleep at night and I'd be happy I mean this is the people like if you could just like go you know what dark matter doesn't exist at all yeah with some series of alterations you'd be fine with that yeah I'd be so happy I'd be so happy because I you know I think the fun part is knowing things like that you know where you can be like it's it's this whole thing it's not that that makes it way more fun even if I was invested in one of these ideas uh but I try to you know stay away have an open uh kind of mind so that I don't get down into one idea because I I really think that's like the killer especially if you want to have like a if you want to be a scientist I don't know you can't just do this um getting into one bandwagon and I feel like it's a trap that you tend to fall into if you want to focus on your career as a scientist what do you think causes that trap I think it's part of the career path um if you want to get you know I just finished my PhD like last month if you want to get even even if you want to get a good PhD or you want to get a good post-doc position right and then after a few postdocs you probably want to apply for a faculty position um you need to be probably an expert in one field nowadays um back then maybe you could you know maybe if you're crazy enough you could be an expert in multiple Fields but you need to be an expert in one field and then you know you get your faculty job you become a known person in the field and then now uh some 20 year old kid comes and tells you no you know look what you've been doing for for a few decades is wrong right and I think it's a very human thing to be a bit defensive um about this and so people are not willing to kind of accept and then let go and be like look the kid's right you know um I think it's part part of like a human I don't know a defensive thing that that ticks off um and if you if you don't jump into one of the bandwagons then um it's gonna be harder to progress your career I I think that's what I've heard from other people um yeah but at the same time you get these you know I think scientists love to hear these stories where after working for decades in you know uh against the resistance someone was able to prove that gut bacteria leads to ulcers or that uh plate tectonics is correct or you know there's all of these ideas that that in hindsight are are accepted by the scientific community and it was just a difficult Hall to to get you know that's it's like Einstein's a relativity it wasn't really accepted you know he never won a Nobel Prize for it yeah now if you ask someone on the road they'll be like yeah you should have got five Nobel prizes right he didn't eat in you know for each one of his papers and the and the anus mirabilis he should have got a Nobel Prize for each one of those it's the pillars of modern physics yeah the guy did relativity and quantum physics and then you know people were like no relativity is wrong even after uh you know they looked at the solar eclipse and saw the uh the lensing I mean there was a lot of proof so yeah you got to fight through the uh the resistance sometimes and and um there it's a skill I guess it's a skill because people are going to be um you know looking down on your work or just constantly saying no you're wrong no you're wrong um You Gotta Have be able to handle that and to keep going I guess but does that like you know when people are telling you that you're wrong and and that makes you sharpen your own skills ideally yeah that you're like you think I'm wrong I'm gonna prove that I'm right I'm gonna go back and I'm gonna double check I'm gonna fix every single mistake that you identified and provide do even better science yeah so do you think like just on average like like I can totally get why 20 year old 20 year old coming into this would be like I'm right like why won't you people listen to me right yeah and they're like well come on we've been doing this for a long time and yeah and we have a certain amount of wisdom and you might be right yeah but you're probably not right so let's just start with you're probably not right yeah and the time in scientific method is is encouraging you to take that as well and to push through even though you might be wrong or are probably wrong right right no yeah that's uh definitely the attitude you need to have as well you know whenever you get criticism the first thing you want to do is to ask yourself and then go through those questions and see if that's gonna help you make better work um so definitely you need that attitude yeah because if you don't then you're not gonna um you know if you end up being wrong then you're not gonna learn from it um if you don't have that attitude so that's important um so then there's a lot of good good criticism out there and then there's some which is like there's no Foundation to it those ones you gotta kind of so this is the attitude we needed actually to get this paper published um we you know even with all the uh very harsh comments from the ref some you know one of the referees we were like okay you know we're gonna try our best to address the comments we didn't like argue back or something like that we're like we'll do our best um to to address the comments and then the editor was like look it's good yeah yeah and it was in nature astronomy like just like just just so people understand like your paper was published in nature astronomy which is right you know a pretty good paper right well I I think it people got excited about it because we were like look we if we use this wave Dark Matter model we can resolve these lensing anomalies that have plagued the field for decades uh it might be you know able to solve anomalies I want to talk about gravitational lenses because I'm a huge fan of these I mean we don't you know if if they're mostly made of Dark Matter then we don't know what they are but we can use them as a telescope which is crazy to me yeah yeah what what are some of the mo like apart from your work that you just did what what are the sort of like the best uses of gravitational lenses do you think honestly yeah it gravitational lenses are pretty much Cosmic telescopes right that's the the phrase We like to use um and really it's sort of like a magnifying glass you you the way we're using gravitational lensing in our paper uh and people who study dark matter it's kind of the the opposite of what you normally do with lensing where lensing actually what it does is it lets you see something you could never see if it wasn't lensed it would it wouldn't be magnified in the sky like a magnifying glass and then what that lets you do is study the object you know that's far away right but the what we're doing with dark matter is we're studying the object that's doing the lensing right right so it's like you're right you're looking through telescope and you're using the image to figure out whether or not your glass is good exactly right that's a good analogy you're trying to figure out what the mirror of your telescope is exactly uh but you know lensing does a lot a lot of cool stuff when you know with respect to um techno signatures one of the ideas that I had which I'm working on is um trying to find out you know trying to look for signatures of wormholes using gravitational lensing so wormholes have a very distinct signal they leave behind a distinct signature when they lens something so it would be different to black holes or galaxies or stars or planets there is a distinct signature and then if you look look for the signature in light curves of micro lensing for example you'd be able to see this and um there hasn't been any search for it there's a few papers that predict what it should look like yeah I remember I know we reported on that a couple of years ago that there was uh some proposals that if there are wormholes then you would see them through gravitational lensing right right um and then the Event Horizon telescope in their paper they also looked at you know what if what we're looking at uh is not a black hole but a wormhole so they do consider um different exotic objects that's what it's called uh but you know with lensing what you can exactly like we were talking about you can study the lens or you can study the the source um it's kind of like a two-way thing and that that's already incredible because in astronomy usually you just end up studying one object what is the power of the lens like you know in terms of magnification um it really depends it really varies and then uh some of these Galaxy lenses the magnification can be hundreds in some areas in in these um special regions called the the critical curve that's sort of where the um image a circular image would form that's what we call an Einstein ring um you know it can be hundreds uh uh you know a few tens on average maybe but if you looked at if you were talking about Galaxy clusters then you know you can go into thousands wow um and then depending on the size of the object there are some studies that look at uh backgrounds you know Stars being lensed and the magnifications can reach tens of thousands fifty thousand imagine you know something being magnified by fifty thousand times um that that would that would be that's insane that would let you see so far back yeah like imagine the Hubble Space Telescope and then 50 000 more of them bolted together that's a big telescope and you know I didn't I didn't I forgot to mention this but lensing is a particularly powerful uh probe for dark matter as well as you know for looking at things because the light just traces the uh the mass distribution you don't have to worry as much about all these interactions and complex things going on in a Galaxy which other people have to worry about if you know if you're talking about uh you know for example the missing satellite some people say that um there's all sorts of you know outflows and interactions between dark matter and normal matter and then if you don't take those into account then you can't ex you know you can't really solve the missing cellular problem but in lensing there there aren't a lot of outs you can't make a lot of excuses basically um and that makes it fun because you can't just tweak the knobs and then explain away something right so it's a very clean you know clean test bed like the lens shows what it shows it's right yeah it shows what it shows so you can't mess around um too much I mean back to that idea of like exoplanets with gravitational microlensing like it's just it's so and I think it's the same thing right that you are you are using a foreground star to image a background star but it is the planets orbiting the foreground star that affect the cost variations in as the lens is going past and it's so sensitive that you see these warpings of the brightening the brightening of the of the background star that tells you oh you know there's a planet it has half the mass of mercury oh second planet twice the mass of Jupiter oh third planet it's a terrestrial planet and then now we never get to look at the gravitational micro lens ever again like I hope we yeah I hope we were recording because it never comes back yeah right yeah yeah and it's that sensitive like the most this in many cases the smallest planet's ever seen are are in these micro lensing the lensings is just is so fragile and yeah it's so sensitive frame yeah yeah it you know the these little Peaks the equipment that we have you know the technology that Humanity has right now it's it's it's sensitive enough that you can see that these these Peaks being made um and you know that is incredible it's it's not something you it's not a conventional way of observing things what does it take to D like I guess reconstruct the image that you're seeing from a gravitational lens like when when you see tan Einstein ring and it is this blur all the way around the lens can you turn that back into a picture of a galaxy or can you just get you know are you looking through the smear of a galaxy and you can make some inferences from that no you're right you can turn it back into the image of a galaxy and then in the field people call this the source reconstruction you just reconstruct constructing the source Galaxy but to do this you need a good Lens model and by Lens model it just means the mass distribution of the lensing Galaxy because you you need to know how to map back the Einstein Ring image into the the original Source right um so you can do that and you know we kind of have to do that for um people some people doing lens modeling do that it's just it's there's quite a lot of degeneracy involved because it depends on your Lens model so you never really know if what you're uh you know reconstructing is the true um is how the true Galaxy looks but you can definitely do it if you had a perfect model of the lens from like really good observations right then you could perfectly create the object that's being lensed yeah yeah and vice versa if you knew exactly what the object that was being lensed was you could create the perfect Lens model exactly exactly yeah yeah right um and then you know that's that's one of the incredible things you can do so some of the work that you know some different work we're doing we're trying to do this kind of source reconstruction to see what the um the background Galaxy looks like and you can you can tell you can do a lot of science with that even even if you don't know if your Lens model is the perfect one you can do a lot of science with that you know you might be able to distinguish between a spiral galaxy and an elliptical galaxy uh you might be able to you you will know the size or at least an upper limit on the size um and then you know you can you can do a lot of science with that stuff do you do you think that we will get to the point where you can like see a picture of a spiral galaxy it looks recognizably like a spiral galaxy as opposed to you know it has enough signatures that tells you that it's probably a spiral galaxy and not an elliptical galaxy like do you think yeah can we make better lens models I mean that would be so cool I I to my knowledge I don't think anyone's reconstructed a spiral galaxy yeah um I think you know we we definitely should be able to do it I think I don't know when you know maybe what would it take to make the best possible Lens model is it like a is it a bigger Hubble Space Telescope to make observations on the lensing Galaxy what yeah what you would need is a very nice observation of the lensing Galaxy and then usually this gets harder and harder as you go to higher as you go further away as You observe things that are further away because the lens images start to outshine the lensing Galaxy so it kind of disappears so um that might not even you know the telescope might might not even matter too much at that point but if you if you could manage to image something a bit closer and then yeah you know if you had a bigger telescope that really and then you observe in different wavelengths so you know multi-wavelength observations that's what you need and many lenses don't really have it you know some of these like I said a handful have radio and Optical but you know if you could do it in in a wider spectrum and you really saw all the structure that's going on and you'd be able to make an incredible Lens model at least the data is available yeah I'm gonna Channel some questions that I've gotten from my viewers for you for a second here yeah um have we ever seen a double lens um by double lens does that mean there's two background galaxies being lensed by the same foreground Galaxy no that there's like one lens magnifying another lens magnifying something behind that oh like a line and a line of line yeah yeah yeah um to my knowledge no no okay yeah I didn't think so either I like I did I searched through the literature I couldn't find any examples where you had I mean it would be phenomenal right because then you would get yeah 50 000 times 50 000 or 10 100 so right so this is a very interesting question because even if you saw one you might not know that it's a double length you get it because you you don't know one thing in lensing is you don't know what the true brightness of the object behind is because it's being magnified by a certain amount right and if you don't have an you know lens models have a problem where the the magnification you can change it it depends unless you break it with some uh some specific observations so you you might actually be seeing a double lens but you might actually not know that this image is being double lensed so you could see you could see an object and you go that might be a spiral galaxy or it might be the uh the stadium of an alien civilization uh we can't tell right right yeah so you know uh I feel like you might be able to help distinguish with um spectroscopic observations so you need like emission lines and absorption lines so that you could determine um but that's something interesting I don't think we've ever I've never come across a double lens situation maybe there's one in literature but yeah yeah it's interesting because uh you know yeah um right so I want to say that you know data there's there might be data which has double lenses but we just don't know how to uh look you know look for them all right well you know I'll dig up the person you asked me that question and then you can you can add them as a contributor on your paper when you okay yeah when you hear Nobel Prize um and then the other one is how Dynamic are these like cosmologically distant gravitational lenses like we know the micro lenses change over the course of say a day as the as the Stars line up perfectly and you get this flare and then it fades away how Dynamic are the ones that are at these cosmological distances do you see changes over time right so then you know that that's something interesting that's kind of started to become a Hot Topic when you talk about Galaxy cluster lenses which is what you know the jwsd the first image it released is a Galaxy cluster with all these incredible lensed images and structures and then right right yeah yeah um and when we look at these Galaxy clusters with better and better observations and you know more observations so you kind of can make like a like a video right over over like a decade and then you realize these things light up like a Christmas tree they're pretty much blinking the lensed image you know a large lensed image of a of a galaxy of a background Galaxy it has little uh you know it blinks in certain places along the image um so that that's people think that's because of micro lensing that's one explanation but there's also it could be melee lensing which is just Landing by a slightly more massive objects like these sub Halos or the density fluctuations predicted in wave dark matter um so so these things you know they're lighting up right and uh the time scales uh these can be months and like you said the micro lensing can be a few days or weeks but if it's melee lensing it could be you know months or years uh and then sometimes that it could be even longer sometimes decades it really depends on the configuration and we know the light system like when I know that astronomers look at say supermassive black holes and they see the Christian discs around those black holes and even though they can be hundreds of millions of light years away you're seeing active processes brightening dimming on the order of years months or even years in the in the disk around one of these massive black holes and so you could be seeing that but lensed or you're actually seeing these kind of wobbles and warps as the two objects are passing one another from our perspective yeah you're incredible you should are you an astronomer no no no no no that's 25 years uh then you should just hop on and you know into a research group because uh you just hit it on the on the on the head because that's what people do uh when they measure the Hubble constant you know for for cosmology when they when they infer the Hubble constant using lensed quasars this is this is this is what they do they track the you know they stare at a quasar at a lens Quasar so there's four images and then they look at the variations and brightnesses of these images which happens because of uh the variability in the accretion disk like you said which we think and there's different there's a time delay because that the you know when the Light reaches you depends on the mass distribution and then so there's a delay between you know all four Images don't brighten up at the same time there's a delay and then this delay is what lets you infer the Hubble constant um so it's so it's important that you know that this delay is because of the uh variability you know in the accretion disk and not because there's something uh in the lensing Galaxy kind of amplifying it and and there's an amazing piece of research where people are watching this Superman oh sorry the Supernova pop off in a in a lens Galaxy and they're seeing it happen with various delays over the course of right multiple years and so you can even predict like on this day we should see the Supernova appear in at this portion of the image yeah and we can watch the entire cycle like right normally you can't see Supernova you don't know the progenitor of a supernova until after it's happening now it's too late but now through this lens they'll be like watch here and you'll see it the whole cycle right yeah it's incredible uh so one of the people on this paper is one of our collaborators as well and um I don't know if you're talking about the same one but yeah there's one where they predict the image to appear in 2037 or something like that yeah yeah that one so it's incredible it's it's so cool um let's hope people remember what if what if people forget it's like uh it's like 14 years later this will be after post Singularity the computers will remember ah okay yeah I'm happy with that yeah that sounds awesome um well if people want to uh track your work uh what's the best place to do that um well I'm I'm on Twitter um and I post about yeah and I post about our stuff uh about our research um that would really be the best way if I'm not I'm not too active on on anything really um or you know archive and then white people post or nature astronomy oh well you know yeah it may be in a decade yeah what uh what is the other um and what's the game you you mainly play oh I you know I play a lot and um I play DotA too okay I don't know if you know DOTA it's like League of Legends but yeah but yeah yeah so what's your name what's your what's your favorite mean on Dota 2 my favorite what what's your favorite what's your favorite hero hero uh yeah Juggernaut you play Bentley Juggernaut okay all right Juggernaut yeah but you know I play I play a lot of others but I also play um valorent I don't know it's if you know it it's by Riot yep um so these are all competitive multiplayer games I prefer support personally but right but right that's okay yeah you you mean you mean reels for it no support like no no like like you mean right support yeah you play that's incredible yeah you know we should play sometime no way Crystal me crystal maiden and Juggernaut you know that's like the best combo yeah no way you would you would it would be yeah sure on the same team yeah but no thank you um well it was a pleasure to talk to you uh I really appreciate it pleasure was mine it was great to talk both about sort of your work but also uh the just how great gravitational lenses are I'm I'm a huge fan yeah and uh and hopefully so many new discoveries will be made from this including wormholes I'm happy to take one and then just get out of here you go Nobel Prize is all around yeah yeah and then away you go we'll see on the other side of the universe all right good luck thank you you know thank you so much uh Frazier um we'll talk to you later for giving this opportunity yeah you can get even more space news in my weekly email newsletter I send it out every Friday to more than 60 000 people I write every word there are no ads and it's absolutely free subscribe at university.com newsletter you can also subscribe to the universe Today podcast there you can find an audio version of all of our news interviews and Q and A's as well as exclusive content subscribe at universeto.com podcast or search for Universe today on Apple podcast Spotify or wherever you get your podcasts a huge thanks to everyone who supports us on patreon and helps us stay independent and keeps ads at a bare minimum thanks to all the interplanetary researchers the interstellar adventurers and the Galaxy wanders and a special thanks to just Paul Davis Vlad shiplin J Dennis David Gilton modzo George Jeremy Mattern Jordan young Tim Whalen Dave veribioff androm gross and Josh Schultz who support us at the master of the universe level all your support means the universe to us

Channel: Fraser Cain

Views: 24,104

Keywords: universe today, fraser cain, space, astronomy

Id: M7IO6FkHRhE

Length: 57min 48sec (3468 seconds)

Published: Mon Jun 19 2023