Here's Why GAIA Is My Absolute Favourite Space Telescope

if you've been watching my channel for a while you know that I am absolutely obsessed with the European space agency's guia mission this is this 10-year astrometry mission where this spacecraft is measuring the position the motion the chemicals of billions of stars in the Milky Way building this really comprehensive 3D map of everything that's around us and astronomers use this data for all all kinds of incredible discoveries uh about in so many different aspects of astronomy understanding the mergers and the the Motions of stars that are on Escape velocities and our position within our arm of the Galaxy and it goes on and on and on it's too much to to say but fairly recently astronomers discovered in gadata a fairly massive black Cole fairly close by us they were able to see the sort of swirly motion of the the star because of a large black hole that was nearby it and this was covered widely in the news we covered it in space bites and after I posted space bites one of the researchers who worked on that paper reached out and said oh do you want to talk some more about the discovery and I did but I really just wanted to talk about guia I have so many questions about Gia I want to understand more deeply how this amazing Mission functions and so uh I was able to conduct my my dream interview about Gaia so my guest is Dr Barry Hall he is uh a research associate at the University of Geneva he's an astrophysicist but specifically he is a Gaia data specialist and so he's one of the people who is working behind the scenes at all of this Gaia data and trying to normalize it trying to weed out any kinds of problems with their system with their data and prepare these giant data packages for astronomers and they're working on the fourth release which is due at some point in the next year or so and we talked about sort of the history of astrometry how guia functions and go into enormous detail about all of the instruments and exactly how this Mission works and gets the kind of data that it does what its limits are and then of course what I like to do what comes next what are the kinds of missions that could follow on in gaia's footsteps and give us even more data about the Milky Way about stars in other you know in other wavelengths that maybe we can't see with Gaia so the one downside of this interview is we actually don't spend very much time on the black hole Discovery at all it's black hole it's kind of close by found with Gaia we talk about it a bit but more it's about the mission itself so enjoy this conversation with Dr Barry Hall Barry when did you first get involved with the Gaia Mission well that was actually when I started my PhD which was in 2007 so so I've been 18 years in Gia um so I I did my masters in in lien in Holland I'm Dutch and afterwards I was looking for interesting position and there was something about Gaia and uh it was not launched then yet it was was early stages and I applied and I never left basically because there's so much to do in the the mission that's that's basically it yeah it's funny to me like my audience knows I'm absolutely fascinated with this Mission uh you know we have a bingo card that whenever I mention Gaia then then they they choose it um and and I think it's because I I love the idea of surveys of databases of repositories of information that then astronomers who have some question can instead of booking time on a telescope look at thousands of examples of that thing so like what was the goal with Gaia to try to pull together as much data as as humanly possible yeah Gaia is a is a real survey Mission so we we set out to basically map map the Galaxy it's it sounds big and it is Big so uh in principle Gaia will is observing about two billion stars which is about 1% or so of the full Galaxy so that's a significant sample for astronomers for sure uh and the idea is basically to to provide in in multiple domains and we can come back to that in photometry in radio velocity uh and in retry that's that was the main mission objective initially uh a catalog of all these objects where people then can indeed uh do searches on whatever they are interested in um and so there goes a lot a lot of uh effort into calibrating the raw data from the satellites and then producing in that sense different cataloges which we then release in what we call data releases so we had three up to now the fourth one is coming in maybe two years or so right um and so let's talk about the process so you know I think you know we're roughly familiar with this idea of astrometry of photometry you you're measuring the movement you're measuring the the location and distance you're measuring the the changes in in brightness and and maybe even what it's what's made of but but how does Gia perform these these functions with so much accuracy yeah well it's a technical technical feat uh which is is UN Marvel would say because if we if we look at the history of astrom astrometry so the measurements of stars the position measurements um basically we were the instruments from from Earth were sort of limited they increased slowly still but we have this atmosphere which is blocking us most of the time and we need to do Adaptive Optics Etc but if we want to make a global map of everything we need to go to space so the first mission that did this was hip paros which was launched in ' 89 and was operation till 93 and it was basically a precursor of Gaia to do the same thing but then so hi parus actually made an improvement of about a factor of hundreds and Gaia did another factor of hundreds so we are measuring with Gia just to give you one of those ridiculous imagination numbers if if you look at the a coin on the moon as seen from the earth that is the kind of final Precision we can get on on positions with Gaia for for for like fraction of the Stars which is unprecedented and and with that you can discover a lot of things like if there's something going around it like a planet or or a black hole um so um and and your question was yeah so how much what kind of processing and how does it work so so Gaia basically goes with the Earth around the Sun so if you have the Sun the Earth and then you have actually a point the lrange point to which is moving with the Earth around the Sun and Gaia basically looks away from the Earth and the moon so it doesn't get blinded like some satellites that go around the earth um so it basically has an unobstructed view of most of the sky all the time and then it spins continuously every six hours and it has two big telescopes which are combined and the combination of these this wide angle and all this this rotation together with the motion around the sun give you a pattern that will we call it the nominal scanning law which in the course of five or maybe now with extended mission 10 years will give you a quite uniform distribution of observations on the sky so every point is observed roughly 100 times over this time span so we measure our position of the star at all these intervals which has an interval of of a Cadence of maybe two to to four to six hours and then maybe 26 days and then up to like five or 10 years and by combining all this data so it's very sparsely sampled as well people are maybe used now to for example Kepler data where you have observations of photometry which are very regular um but we we actually have very sparse data so it's it's both a challenge because it's not easy for example to search for periodic signals in this kind of data but on the other hand it gives us a lot of uh information about all these Stars so um yeah we're trying to optimize this to to harvest and get the most out of it so a break these down piece by piece so you know guy is at the L2 Point as you said it's orbiting around the earth so it's spending time on one side it's orb on the sun yeah it's orb on the sun it's spending you know it's it's on one side of the sun it makes a series of observations it's on the other side of the sun it makes a series of observations on the same so so you've essentially planned out all the parts of the sky and then there's like a schedule that when you're on in this position then these are the stars that you're checking from from to build The Parallax view yeah so in in principle um so the it has two fields of view as I said which have an area of roughly the uh the the moon size as uh as area and the satellite is is spinning so it's going around every six hours if you would leave it like that it would just make a band on the sky of what is it 7 degrees width now due to the procession There's A procession of the the spin axis of the set satellite so so the satellite actually is um it's like a head structure so the head The Backs side basically protects it from the sunlight and behind there is a tent where the telescope sits and it's always 45 degrees away from the Sun so it's always in the shade the tent is behind here and um there is actually a specific motion that it it uh it rotates like this and then also around the Sun and this combined motion gives you that uh in the course every half here you see at least every position on the sky but um it's yeah it's basically sampling different parts of the sky continuously so there is no scheduling as such uh the specific thing also is is that it uh it has a we call it a sky mapper everything that is brighter than a certain magnitude which is now around 21 or so in G magnitude it will observe and store in the databas of online uh in satellites and then later it gets downloaded and we try to make sense of this so it it is a in that sense a blind survey anything that pops up so also Supernova or whatever might be there it can pick up and it actually has done this as well so um and and so then you're getting this continuous observation you're you're pulling all this this data back and so we talked about the idea of the say for the astrometry to find the positions of these the distance and location these Stars you're getting about a couple of observations per year for each one of these these stars and then same thing like say with the photometry you're getting a handful of observations of each star each year that then over the course of the full data set will then be you'll be able to provide say a 100 observations of this of this one star yeah that that is correct yeah yeah yeah and um maybe just going a bit in the astrometry part of it because the the whole thing about astrometry is measuring the positions and distances to Stars so so how do we do that because we we basically use the motion of the satellite around the Sun so it goes One AU on one side and One AU on the other side and just like with your two eyes you can basically distinguish if you close or open one and something is closed by or far away it will seem displaced with respect to each other and we use this one Au Bas line on both sides to to see how the stars with move with respect to to each other uh and now this one Au is very small with respect to the size of our our galaxy so therefore we need this ridiculous Precision to to actually with this one Au we can actually see the brightest stars on the other side of our galaxy wobble a little bit during the year this is incredible if you think about it but that's that's what we're doing with with Gaia yeah I mean the recommendation that I always make to people to wrap their mind around is to hold their arm out put the thumb up and then just open and close each eye and you'll notice your thumb jumping back and forth and so imagine each of your eyes is on either side of the Sun and your thumb is the foreground star and the background is the background of the universe and you're watching your thumb jump back and forth and you could measure that and you can calculate the distance to your thumb just by how far it moves back and forth um but but you know it's not just the location how do you get the the speed and direction of the Stars yes so as part of astrometry we we measure the position of stars repeatedly so what do stars do on the sky if we just look up they look static didn't move but in in principle they all are moving which we call proper motion and many people are aware of this of course so in the course of time some Stars actually have quite a high proper motion so you you can see it over the years several Arc seconds or so to like Barnard star is is one of those examples which you can actually with your backyard telescope over the years track the motion so if you to first order everything of course revolves somewhere around in the Galaxy around the center but we are having a very short time span so to first order things look to to move linearly in space so that is the proper motion that's the first order model we make and then um by measuring over time the position of each star we can see that okay there is a linear motion now what we just were saying that because due to the parallx we are moving around the Sun so this star From gaia's perspective or our perspective is not moving in a straight line but actually it's making a wobble while it's moving so it's it's going like that so every year gives you a wobble and this wobble is proportional to the to the parallx so the further away the smaller the the this wobble is now if for most stars this is basically the motion that we can see uh and also of course somewhere in the middle of that time range that you have data you put a position so you you define a reference time and that gives you the position at that time so now we have position proper motion and the distance encoded as parallx but on top of that many stars are not single so we have a lot of binary stars or things with a planet around or a black hole so there's an additional motion of this star on top of this motion that I just described and um this is of course where things become really interesting and where we're trying to to build catalog specifically for these kind of uh components uh that might be going around so um for example uh I've been involved with the work on detecting exop planets so these are the tiniest of motions because what you have to imagine is that we have a star and a planet the planet is super light is not bright so the Dominate the dominating light is the star and the planet is light so the mass Center of mass is very close to the star so the star will do a little bit of of this wobble and we need to detect that very tiny wobble so we cannot do that very far out but actually we can do it up to maybe a few hundred parac or this is several hundred light years which is actually very far um and of course if the the component that doesn't give light off is a black hole and this is the star which is the case with the black hole 3 for example what you see is nothing here but you see some start doing a crazy motion like this and and that of course is a Telltale sign of of something very heavy being there which we we cannot see yeah yeah this and this you know was big news last week that that guia had uncovered a fairly massive black hole the closest one here in the Milky Way and the most massive Stellar Mass Black second closest but yeah uh oh second closest okay almost the one it was also gu yeah and I'm sure that that record will be broken at some point sure yeah yeah yeah yeah um so so you don't use red shift at all to measure the the the motion the proper motion and and the motion towards or away from us at all it's purely just based on yeah so uh well with red shift you maybe you specifically mean radio velocity of the star yeah yeah well even just I mean not for for the Planet side but just from like when you're measuring you know like Hubble famously measured the how fast the galaxies are receding based on the red shift of the of the light and so I guess if the stars motion is constant you don't really get a big red shift change from the Star right yeah so so red shifts are are we see the light spectrum really shift a lot when you go to to extragalactic uh objects because they receive a lot but I mean the the effect is obviously the the same but we indeed measure with guy also the radio velocity which is basically what what is called the red shift for for these extra Galactic objects which is the motion indeed radially from you and and with Gaia we have actually also a spectrometer on board which measures for the brightest stars this radio velocity and um we actually for example with black hole 3 we could detect it both in astrometry so we see the motion on the sky but also we see the radial effects so we have some very nice plots of the orbit basically being plotted on the sky of the astrometry and then the radio velocity which has a specific shape due to the ticity of the orbit follows exactly the pattern that you would expect for this system so it was a a very nice combined um measurement where we could validate using the rate of velocity independently from the the astrometry to to validate that it was a correct measure right yeah but but the number of stars that you get the photometry for is less than the number of stars that you get say just the proper motion for like are you able to measure the the the chemical signature in every single star that's in the guia database or is there a subset yeah that's that's a very good question um so for that we need to go in a little bit more detail so because to to determine the the spectral um features usually we think about taking a spectrum high resolution spectrum and then checking the lines and then measuring the the abundances of the the different elements now the Gaia spectrometer uh has a high resolution but it can only work up to magnitude 14 or so or maybe 16 when you average them and Gaia goes to 20 21 or so so that's really a lot more um but having said so and also that spectrometer is very uh Limited in range it is actually built to detect what they call the calcium triplet and because those are lines that are visible in in most of the spectral type Stars so all kinds of types of stars have it and they are then easy to to determine this radio velocity or this red shift so to say so there are some other features that can be detected there which can lead to an abundance or particular elements but maybe not so many but what we have in Gaia as well is that um we have a red and a blue photometer we call them it's somewhere between photometry and spectroscopy because the it's it's like a a prism so it disperses the light uh and we have a resolution of about 60 so it means that from from red to blue you have like only 60 points so you cannot resolve individual lines or anything but you can resolve features and this is actually used to characterize the the the specific specificities of the of the different Stars what kind of type they are what kind of uh abundance of elements they might have so in that sense we can classify stars and this data is available up to the faintest magnitudes maybe it becomes less useful below magnitude 19 or so but in principle these red and blue photometer data which are just lower in resolution but therefore you need less photons to basically analyze them uh is available in Gaia up to for for a very large number of sources so we can actually get a lot of information from that so that would let you say classify things and go oh these are some main sequence Stars these are some white dwarfs those are yes super Giants and then and maybe a a rough understanding of some of the chem some of the really bright chemical signatures in those stars but you're not going to get the kind of sensitivity to say show me every Star that has this absorption line for iron in its atmosphere or whatever exactly yeah right there's there's a whole group working in Gaia just to to do this to to use all the Spectra in detail to model everything to figure out for every Star the best possible guess we can make of uh of all these things yeah and and I know there are Partnerships that the guy works there are other surveys that are doing exactly the more detailed spectroscopy and then you match them up and now you suddenly get the location the direction and the chemical signature of the star and and people have been looking for twins of the sun try to find our our Stellar companions from when we were in the nebula which is which is really cool um so so I've got a sort of a good sense of of like the instruments on board the way the science operations work and I want to just talk about some of the of the limits so um you know it's two billion stars is um do you think with a longer survey like if like when Gaia data release 4 comes out spacecraft is still okay you keep going do you think there's sort of a theoretical limit that will finally be reached on just how many stars are even feasible to be seen yes so I think the the two billion is is sort of maybe it's 2.2 or so of stars that guy effectively can see so uh because there's a whole problem of crossmatching all in idual observations to the same source to to to identify every Transit that we measure because we have trillions of transits I mean it's it's crazy if you think about the number of observations um so about extending so the thing is that um so we will not probably get more than this two2 billion from Gaia um basically if you want to extend more you need to for example go to uh near infrared which we can talk about as well that's a yeah I want to talk about that yeah I I reported on on the near Gaia uh near guia guia IR anyway we'll we'll we'll go into that and um guy in here there we go yeah um but but I want to talk about then sort of this idea of the exoplanet so yeah yeah yeah one of the big I don't know not promises exactly but one of the really exciting possibilities was that Gaia was going to turn up a lot of exoplanets with astrometry we've seen some interesting candidates but we haven't seen the thousands and thousands yes are they in that data do you think will will data release 4 bring us the Dela planets yeah we're working on that right now and um so I could tell you that for sure there will be uh I guess at least hundreds if not thousands also not only planets but also Brown dwarfs which are the sort of in between planets and and and stars uh to be expected indeed the the predictions that that uh different papers uh have have given is like thousands or tens of thousands of these kind of objects uh I think that we will get to maybe thousands or so hopefully for dr4 at least at least hundreds for sure um and that maybe we have to wait for D5 to to get to the highest number and it brings me to the point that you you made like um about the length because one thing did not talk about is that the guia mission of course progressed while we also were processing data and making data releases and what basically happens this guy is still operational but probably will cease operations next year so it's not because well it has two kinds of consumables one to keep the uh spacecraft in orbit which there is still sufficient as I understand but the other one is to keep the the very precise motion that it's doing to keep the satellite spinning in the right direction Etc and that's running out so about slightly more than 10 years of data we will get now the point of course is that for every data release we started with data that was calibrated a bit before so it was short so we started at some point we 22 then 33 months now uh the4 will be 66 and then the next one will be 120 or so so we basically double almost every time and with this doubling we extend the time range over which we can see stuff so for example just just as an example the black hole 3 had an orbit of about 11 uh years 11.6 and that's on the upcoming dr4 data it was a preliminary version uh which had roughly half of the time span so we could see the orbits half of the orbit and that was enough for us to to confirm it so every data release we have more data which is longer data and better calibrated so the good thing would be if we can indeed if we would have a way to refu uh the set light to to continue it for for many more years just because of when you extend the Baseline you get much more data especially for finding exoplanets which we we want to find not on orbits of only a few years maybe tens of years so the longer you go the longer you can detect them and so that's different from the finding more stars like there's just a limit to the sensitivity that guia can reach but with the exoplanets more time is better yes yes yeah yeah yeah so that's one one of the other reasons why we in dr5 probably will have much more because also yeah every orbit is basically a validation I mean the the noise goes down you you are more confident um one of the things if I can give you detail of the kind of things we we don't want to publish so because the the the team I was involved with which actually identified black hole 3 is trying to to look at things that that look anomalous so if we have an object that looks like a a black hole or actually one of the things we found in the previous data release was many super massive black holes supposedly if we believe the mass so obviously that was not the case but then you go back to the data reduction and you find some Corner cases that okay there was an outlier here not not taken into account and then suddenly well High masses are are the easy thing or or orbits that look very big are the the the easy thing that can go wrong if you have a an error in some of your data so in that process we basically managed to to reduce a lot of the the systematics that we uh do in our data processing and therefore increase the the accuracy and um we actually wrote a paper on on something called scan angle dependent signals which which sounds extremely technical but the interesting thing is that because Gaia as I told you it's it's rotating in a certain direction and the guia mirror is it's doesn't take pictures with a circular telescope it's like rectangular which means that it has a high resolution in the direction of the the scanning and a much lower in the other direction it has basically Hubble kind of resolution it's like 60 millarc in the in the direction of the scan uh Precision uh of of measurements on the sky and the thing is that Gaia as I told you about how it scans the sky it it has some kind of complex motion which makes that if you look at a particular star that sometimes it goes like this sometimes like that sometimes like that so it scans in all kinds of directions and it's mainly one-dimensional measurements that are used especially for astrometry now the issue is is that if you have a pair of stars which are very close together and you you go in One Direction over this pair of stars that in this direction I can resolve them because my my resolution is high enough to see them but if I go in this direction I don't see it and we found out that in our data um data reduction analysis uh this this problem of not knowing when something is is seen as double star and sometimes not gives a sort of artificial signal so to say that that makes it appear first of all variable in in in magnitude and also in astrometry it looks like it's wobbling so it could actually this is one of the reasons why it looked like some orbits existed which which were spirous completely SP right so so it has better Vision in in some angles than other angles and when you finally you and you have to account for that now in all the observations was this was this looking at stuff with its good eye or its bad eye yes yeah in some way yes yeah yeah and you have to combine them because you you use all the data in the end and uh so it's it's another interesting fact I mean not many people probably know but uh we I'm also involved with the variability analysis of Gaia so we we look at variable Stars we try to classify them if it's seit or or if it's a Galaxy or supernova and one of the things that turn out due to this effect is that because most of the galaxies if they're far away I mean they're hardly ever circular they have a sort of elliptical core and almost all the galaxies are having a very nice periodic signal or not periodic but a very nice signal as function of scan angle so they they seem to vary in magnitudes but in principle on the sky they they're constant so with the current data release we were actually able to classify because we build classifiers to do this automatically a very good uh uh all kinds of galaxies which was never our goal because galaxies were the the constant stuff was the stuff we we were not so interested in originally but uh so it's interesting how these kind of um features allow you to to detect certain certain other things or or help you uh because in in another way as well about these these closed pairs so these closed pairs can be much smaller than the pixel size so the pixel was like 60 millarc or so so that's 60,000 of an arcc which is the typical uh atmosphere Distortion and um these these pairs can be just a few milarch seconds separated and in principle it would be very difficult to detect them even with Gaia but because of this motion uh this gives a specific signal which from which you can actually deduce that there is a binary or or maybe not a binary but two Optical pairs so some some can be just in the background or something so it just gives you another dimension of using the same data to extract information about about what we're seeing so you know you mentioned sort of this galaxies you know we know Finding black holes exoplanets like there's a lot of surprising discoveries made with a survey this vast and and sensitive so what are some other examples of of interesting stuff either you know clever ideas by astronomers to look for something or just weird anomalies that have POS up that have giving you insights into the universe how has this telescope surprised astronomy Beyond just the expected mountains of data about all the stuff that they want to know about yeah yeah yeah so I think um so I'm I'm unfortunately not able to follow what everyone is doing with it but I I see that in many fields just the basis of having distances to stars to calibrate absolute Luminosity of stars and then doing science with that helps in many respects but I I could highlight one thing that was actually part of the design test that they wanted to do which is with the astrometry so one of the things is that everyone knows that we are moving around the Galaxy uh in what is it 220 kilometers per second and about 220 million years um but what they actually measured is in a period of they used only 33 months of data they could actually see the acceleration of the solar system around the the galactic center so they could measure that it's not going a linear motion of our solar system but actually it was deviating and and this this this is amazing small number I I just looked it up because I just wanted to mention it it's like2 nanometer per second basically the deviation of our solar system is doing and over the year it adds up to about 100 kilometers or so out of the the motion around the Galaxy so we have this this very tiny Ang that we're actually probing and they could detect this with with the Gaia data and I think this these kind of things is is just astounding I mean everyone had ideas and it was actually consistent with what we thought it would be so it in that sense was not a big surprise but just the fact that we can actually measure this with basically a geometric method by by using Paralis and direct measurements of the positions of stars it's crazy yeah yeah I I mean I can give you an example people were able to make a mass estimate of the Milky Way calculating the velocity of stars on Escape velocities that had been kicked out from Supernova explosions or from interactions with the super massive black hole and so they they looked at you know Gaia has turned up these Stars they were able to measure the velocity of these stars and then calculate as they're watching as they're slowing down as they're moving away from the Milky Way to be able to calculate the mass of the Milky Way and it just came from Gaia so they got an estimate of the mass of the Milky Way thanks to to Gaia yeah and and it's this kind of stuff yeah and it's this is also a very new dimension this kinematical space that Gaia gives so with Gaia we get we get these proper motions on the sky we also get for most for many stars this radio velocity so we have a 6D pH space so we have the position and the Velocity in three dimensions and with that you can basically uh retrace basically given that you have a certain potential you can you can work out how the stars have been moving over over many millions of years and maybe further to to trace back what has happened and what people have found basically in this kinematic data is is certain groups and streams which indicate that there have been certain merges in the past which is what what we expected of course but to identify them and just instead of having just this field of stars you can say okay these 10,000 stars that are seem totally random because of their kinematic properties they belong to a certain group or stream of stars that come from somewhere else and and for example for the black hole three this is this is really exciting because um so we had the photometry from guia the astrometry from gu the radio velocity but then also due to the kinematics um it's now expected that there's a stream called ed2 it's a group of stars that are very separated it's a small group which might be uh an old uh globular cluster a small globular cluster so they were all formed together they have a very small metalis spread so they were formed probably from the same primordial gas at some point which and um if you look at that cluster and you put black hole 3 the new guia discovery it's fall smack in the middle so it's it's like extremely interesting because that might tell us where it comes from and and the interesting thing is is that now black hole 3 is in the dis but actually it's moving uh in a Halo orbit so it's it's actually going around it just happens to cross now maybe that's also why we detect it it's it's close enough to us that we can actually measure it properly uh and it's also going retrograde so it's going the other direction then then the rest of the the Stars typically go so this is a clearly distinct uh cluster that's moving around uh and just having all this uh these measurements you can actually identify other members of that cluster and then now people are trying to work out okay was it Formed maybe uh yeah because what's the formation principle was it maybe interacting a lot with other stars in the cluster to exchange maybe components to get this binary component was it Formed like this or was it maybe ejected so there's the interesting thing is that Gaia gives you so many Clues it's not just okay we see something wobble and it's okay it's probably a black hole but it gives you all these other things that you can then try to puzzle together to uh to to figure out what is the history and it's it's nice now to follow the the different papers that come out on this who try to figure this out an interesting thing some people say ah I can explain it with st Evolution this binary formed like this and it it could survive the other ones said it's probably much more likely that it was formed in a global cluster so it's it's it's fascinating it must be interesting though as as a person who works with this data all the time and thinks about the capabilities of the telescope and then you see someone's proposal for an idea to use the data and you're like oh that's so smart I never even thought of that of course you could do this yeah yeah yeah one of the things that that's very satisfying because if you're in the Consortium so to say we have this we build these cataloges but we're not supposed to do science with it in the sense that we we cannot ah this is interesting object let's let's check out what happens no after the data release is out we have the same rights as everyone else so that's when you can start writing a paper for Black Hole 3 by the way we we went through a 10-month uh permission process in Gaia and Isa to get this out before dr4 because we thought it was so significant that we should not withhold this from the community and they agreed but uh so just just to let you know that typically we're quite shielded so for me it's uh it's very nice to be talking openly about all these ideas and and science cases uh that go on but sometimes we go to these conferences where people have this some kind of astronomy hackathon so you you just are together for a week with people who have all these crazy ideas like like what you say things you never thought about and they just put something together and then you can come there as a well they invite people that working guy as well and then you can help them with the details because that's what you work on every day and then like three four papers come out that a few months later are published on on all kinds of topics and that's extremely gratifying and um and nice experience to to do so uh you can really see that the community that that's using Gaia is also growing I mean people just realize how much potential it has for all kinds of uh I mean for for professional Astron like people who are listening to this how how do you get involved in these kinds of of hackathon community events is there a place where they're announced or yeah yeah yeah yeah they're they're typically just uh they're actually people from outside of of Gaia who organize them and basically asked some of us to to join for example but uh these are these are commonplace events that yeah if you look at the conferences list that are distributed people people will find them yeah that's really interesting um so you sort of mentioned that Gia has a finite time for frame I me you know we're all familiar with web's theoretical 10year lifespan probably closer to 20 years thanks to issa's amazing launch perfect launch yeah yeah so do you have a sense when guys's last day of science will be yeah it looks like it might be um somewhere beginning of next year I know yeah yeah and that's that's simply because this um it's the Thruster gas so there's this this very delicate amazing attitude onboard control system which has been working for for 10 years straight which is it's a very interesting system in itself it basically gives a micron Newton thrusts several times a second to keep the satellite spinning at exactly a specific rate uh and motion to follow this nominal scanning LW that I mentioned before and uh this gas basically they can see reliably precisely predict basically when it runs out and um actually they will reserve a little bit to do some some final tests to to do some experiments because there were a few issues at the beginning of the mission which we might want to to figure out how they work by by doing some additional things and then in the end it will be uh shut off in an orbit around the sun uh sort of graveyard orbit where it's supposed not to come close to the Earth for the coming hundred years or so so but um yeah the nice thing it will not crash so it will be will be there for Prosperity later to to fly to with your uh your anti-gravity uh device in 100 years right you can Vis guy and see some history now but yeah so is there like no science that could be done with it just tumbling like it no longer able to maintain this perfect thing like if it's because I know that a lot of science gets done where people go we used all of the in between time from Hubble as Hubble was sing we grabbed grabbed all that data and then we found asteroids or whatever and so it's there's just if it's randomly tumbling it's still watching yeah so the the I my understanding is that the main issue is is that the way the the observations are made so we have um ccds that are fixed and the satellite is supposed to spin at a certain rate and what what is happening is that the CCD has a certain length and effectively the star crosses the CCD in exact 4.4 seconds and in the CCD it has like um 4,400 pixels every millisecond it it shifts the the pixels the electrons from each pixel to the next one at exactly the same rate as the star this this called time delay integration mode so it's not like Imaging like we're used to where you take a picture and then you read out but it's it's like a continuous shifting readout and um I think the whole focal plane cannot operate operate in another way first of all and I don't think we we have any of the the design or the mechanics to to make it into a pointing Mission so this has been looked at of course I mean any kind of way we can extend the mission uh has been has been checked but unfortunately guy is so specifically designed for for this particular purpose of of this scanning motion that uh it will be impossible to operate it any other way yeah I I I'm such you know I always think about these incred Mission extensions things like what happened with Kepler where they were you know after the reaction Wheels died they still figured out a way to use this thing to discover exoplanets or just this week NASA has been working hard to restore Communications with the Voyager spacecraft which are 47 years old right um and and on like who knows how to program that anymore and yet people can can figure this kind of stuff out and so it's always you know everyone always says oh the lifespan of this mission is 3 years or 5 years or whatever and then they figure out something super clever but it sounds to me like no no when it runs out of this gas it's it's originally it was five years we got more than 10 years out of it so I think we're already quite lucky that also nothing broke I mean we had when it was launched it was the biggest focal plane I mean we have like about 100 ccds on board and it's yeah it was and it's been working basically ever since uh nothing really major happened which is amazing as well as this this Thruster onboard control system um we had I mean interesting things that happened to Gaia I mean unrelated to to what you you were saying but it's like micro meteorites so because of course guy is quite a big object and um so when things hit it it will will move a bit or or shake and because guia does astrometry which is trying to measure the most precise positions of stars on the sky any of these little hits is actually uh detectable in the Gaia data and uh one of the the side products of Gaia is basically that we we now know much better the micrometeorite conditions at at L2 uh so I think that that has been useful so for other missions that are going there now because we basically can sort of measure the kind of distribution and the the frequency of of hits that you might get uh in that place um and on top of that there's also Al the radiation damage this was actually part of half of my PhD was on on characterizing radiation damage before guia flew and what was done um people put this Gaia ccds in um in beams at accelerators just to to radiate them to simulate what would happen after five years of exposure in space and it looked quite difficult to calibrated properly and what we find now with Gaia is actually that the total accumulated dose so to say of of damage has been maybe a factor of 10 lower than was originally expected so uh that was a really really good thing because it it simplified a lot of the data uh analysis because um yeah it's it's quite it's a bit technical but in principle you you want to measure for example with astrometry you want to measure the exact position of the star and guia actually measures very uh very little data per star so typically you get a window around the star which is maybe six or 12 pixels wide and maybe six pixels high and often it's it's even collapsed in one dimension so you basically have 12 pixels of points and what we want to do is we want to find the center of that shape to maybe 100 or a thousand of a pixel so you need to know exactly what kind of shape you could expect for these 12 points align it properly now the whole problem with the radiation damages is that it it as I told you the electrons are moved every millisecond from one pixel to the next so you you sort of accumulate over 4.4 seconds an image of this six or 12 pixels and what happens if there is a this these kind of radiation damage causes what we call traps basically they capture an electron and then they release it after a while now what happens if if this if you're building up this shape of the the the star and it moving over over the CCD and there is somewhere an electron captured on one side and then released on the other side then you distort the shape and this gives you an offset which is easily uh a tenth of a pixel or much bigger actually or or comparable to the the pris you want to reach so um to model this properly is is a a huge difficulty and luckily so the radiation damage was less there are also some some ways to mitigate this on board that ruce it so um sorry I'm getting a bit technical so you should stop no no no no no I mean because it's what people normally don't don't speak about but it's it's like it's all contributing to the power of Gaia if all these things were not designed and thought of and and calibrated it would simply not not deliver what what people are using in the end so uh I'm very passionate about that yeah so when it does wrap up next year don't be sad be glad that you got an extra five years and that extra five years it was healthy and strong and doing great science right to the end okay so so then you know we we talked about this earlier but let's talk about what what comes next so how because because astrom like Issa seems pretty committed to having an astrometry Mission ongoing as much as possible with h parcus with um with Gaia what comes next yeah so only real thing on the table is is guy anir so this guy anir infrared so um I'm not directly myself involved but as I understand it it's basically a Gaia like satellite very similar principle also scanning also doing Global astrometry like Gaia but having detectors that actually are sensitive more towards the the near infrared and it might detect instead of uh two billion maybe 10 or maybe 20 billion I don't know so it goes much deeper and um it would be great if we have that uh and and one of the main reasons is not only because we can then finally see all these Stars also that are hidden from us now behind the dust Etc which have have tons of applications of course and very interesting by itself but one of these other things that people don't talk about a lot is that Gaia has basically Set uh an international Celestial reference frame and what that means is basically it has defined the positions the propotions and the parallx of all these stars but the issue is that um this reference frame so to know exactly how fast the star is moving and where it is Will degrade uh when you go further away from the data it was derived from so as I told you next year the data will stop so the best data the best calibration for any other data that is not Global astrometry like Gaia if you want to use Gaia as a reference will get basically has a worse reference frame the later the observation or the further away from from Gaia observations it is so all the observations that are made now will be will be the most accurately calibrated but if you do observation in 15 years from now 20 years from now the proper motions especially will will degrade so you will not have the kind of precision that we have now uh in terms of in in through uh positions and and parales now the point is if you put another mission Guyer which is hopefully going to fly in uh 20 203 45 maybe somewhere hopefully it will be accepted this is all speculation of course but if it would fly then you can do combined solution of guide and Guy near and then you have suddenly a much longer uh span of data and then you can calibrate all this data in between to a very much better resolution so uh it allows you to to put everything in that reference grid which sounds very uh esoterical like what what do you need this reference grid for but it has a lot of applications in terms of figuring out how fast things move absolutely in in in space and also in distance how they relate to each other so it is a very important factor which which is not often mentioned but it it would be if there is no successor then we will be in a sort of we were in the highlight of the astrometry for quite a while I think and this is this is crazy to think about because there are so many interesting big missions coming up but the astrometry itself is something so specific that that it's very difficult to do so so does that that infrared wavelength and you mentioned you know see through the gas and dust see other the Stars so you're seeing stuff that maybe is obscured by too much dust farther out into the Milky Way but it also helps fill in the missing pieces right I mean I when I think about gaia's View and all of those Stars I think about my own view here on Earth when I look up in the sky and I see all these stars that is not a representative sample of the Milky Way that is the bright stars that are tens if not hundreds of light years away from me and they're all ridiculously bright would that that increased capability from Guy give you fill in the gaps in between or allow you to look farther out into the Milky Way yeah I think uh I guess both but but definitely the fill in because in principle Gaia would have the capability of of spotting things uh in the galactic boats for example much more I mean it has the the capability of of of measuring those but it's simply not able to do so because they are obscured by dust so if you are able to have Gaia Precision on stars that you can actually see at that distance so it will fill up I think exactly as you said the gaps there are a lot of gaps in our data if you look at kind of top level view map of what guy has mapped out in the Galaxy there are sort of like this These Arms which sometimes indicate where there are big blobs of dust basically blocking us to see further and and that will give us a much more complete uh uh sensus I think there are many many more science cases but but definitely also The Bu area uh and the galactic center are extremely interesting for for for near infrared observations of course and and other of course other infrared instruments that are coming online or are online can obviously uh do these observations and tie their observations to the Gaia GD which is now very good so in principle you can do already a lot of measurements at the moment but those are usually small angle instruments so you to to survey a whole region it takes a lot of time well this Global Mission like this guy here would give you for every Star basically a sort of uniform way sampled uh all this information much deeper and maybe slightly further away because some stars are obscur which are then brighter because you see to the tust yeah um now you're an astronomer and not necessarily an instrument designer but do you think about like what would be your perfect astrometry machine if you could you know if Money Was No Object um uh what would sort of take astrometry even Beyond say Guyer to the kind of the next level do you think yeah that's that's a very interesting question um so I've been involved with a mission called neit and later it was called Thea where we we wanted to do because guia does um micro second astrometry or 10 Micro second is basically the sort of limit but if you want to for example detect earthlike planets with astrometry uh the kind of signal uh you need for that is is much much much lower so for an earthlike Planet it's about3 microarc the kind of motion around the star so that's that's another factor of 100 basically of what we what we're capable of now so I would be very interested to see instrumentation that can go even maybe another factor of hundreds with respect to Gaia the interesting thing is is that if you do that you everything becomes variable because even there might be some stochastic gravitational wave effects that that start to play at these kind of levels when you go to to Really precise measurements so um yeah or or the other thing I'm also very interested in is like interferometry in space like there there used to be Darwin I think now it's called life but like this constellation of telescopes well I I remember in the old days the Darwin mission was maybe 8 meter telescopes in space or 4 meter which combine and could actually image an exoplanet or something I mean that's that would be would be crazy amazing so um yeah but but the like astrometry is or sorry like the traditional ways of finding exoplanets radio velocity and the transit method they really rely on on the planet and the star and us being lined up perfectly so that we can see only the very the tiny fraction of planets that are passing directly in front of the star or close enough with the radial velocity method but astrometry offers this hope and is you know that you can see these star systems at every angle that in fact the best ones the ones that are that are not where the star and the and the planet line up that you're actually seeing these stars make tiny little circles in the sky as they as they move a little spiral you know do you think that there's a way to get at thousands tens of thousands hundreds of thousands you know millions of exoplanets using astrometry uh yes uh I mean in principle it's it's it's feasible if we keep on developing and improve our accuracy so I mean maybe an interesting side note to what you said is that because for transits indeed you need to be exactly aligned with your field of view so if if the or get longer it becomes very unlikely that a planet will actually cross exactly the dis of the star now with radi of velocity you have more freedom because uh you measure this direction but if the star is inclined like this you will still have a component in your direction although we have this problem that we cannot from R velocity alone cannot know the inclination from astrometry you you know the inclination so that's that's great and the other thing is also that astrometry is actually more sensitive to longer orbits and radio velocity more to to closer orbits because radi veloc is sensitive to the velocity of the star which if you're closer they will move faster and if you go further out they start to move slower so it's it's working the other way around well astrometry because of this Mass center that's basically um causing the star to move around and the planet of whatever you're looking at the wider they are I mean of course the mass Center will proportionately shift but the orbit will get get also wider and the movement of this this system will get wider so astrometry is more sensitive to longer term uh longer period planets or whatever is orbiting than radi velocity so there's a sort of crossover where Asom will give you actually a sort of complimentary sample and this is where where we're hoping to find with guia not only a lot more planets but a whole different zoo of planets because we can probe out a region which is much further from the from the host star um the problem is well of course that what I just mentioned the earthlike planets they have an signal which is non not detectable with Gaia at all but things like Jupiter and higher are definitely within our range and that is why we hope to see at least thousands of planets at least with Gaia and uh for brown Wars I did some estimates it was like in the tens of thousands possibly um so yes if we can build an instrument with infinite money behind then then I'm happy to to go on board and uh and come up with something um the other thing is that of course the obvious thing if you want to improve also the uh the this is more also the the parallx position so if you want to know distances better to other stars we can also go to a wider orbit around the Sun so instead of being in orbit around Earth you you take an orbit around Mars or or even wider the problem of course becomes that to do one orbit it takes you many more years so there's a sort of trade-off if you want to do a mission in your lifetime and get some results um what about two what about two installed on either side of the uh of the solar system system um yeah I think there was once a brainstorm session on this and actually my my PD supervisor lard lran he's one of the founders basically of Gaia he I think he had a very clever idea that if you put two instruments and you accelerate them in opposite directions you can also uh get from that good astrometry of course there's a limit to which directions is best but so you could come up with with creative ways of uh of improving the kind of measurements so you just fly these spacecraft into Interstellar space just in exactly opposite directions into the universe and the farther they get the the larger The Parallax you're able to measure from those two spacecraft in principle yes yeah so yeah I love it that's fantastic yeah how's that coming yeah I think we need to write a proposal for that but uh yeah that's yeah yeah that sounds good that sounds like just the kind of you know moonshot that that Isa is looking for um what are you obsessed with right now well I'm to be honest I'm really just uh uh I'm really involved with with getting all this data for D4 already it sounds very boring but I'm really invested in in getting all the calibrations right and and especially finding these planets because we see how that we can detect them um of course the black hole Discovery also triggered my intention my interest there so I I would be interested also to pursue that in the future more to to maybe work together with people who do the the modeling of how these things can can happen of course because I'm not an expert on that myself but um yeah I'm involved in many topics and I just love the the the way to to optimally use the data so to say so whatever data it is to to understand where it comes from at first principle basically and uh and that that's what drives me actually every day and I I feel like I'm privileged one of those people who got to to got uh to make their hobby into a job so uh yes I I'm I'm very happy where I'm now well I I hope the team knows how excited everybody has been for Gaia so far and and there is a lot of anticipation and excitement for release four so uh keep keep on going and uh we look forward to that next data release thank you for your time oh thank you very much I hope you enjoyed this interview with Barry whole uh just absolutely fascinating conversation about the guy in Mission now I have thoughts but first I'd like to thank our patrons thanks to Abe Kingston andream gross danis alberty douge Stewart Dustin cable Jeremy M Jim Burke Jordan young Josh Schultz Mark Anis Modo Paul robox step kraki Steven fer Munley and Vlad chiplin who support us at the master of the universe level and all of our other supporters on patreon I love Gaia and I think the reason I like Gaia so much is that I really love surveys I love large missions that try to capture as much of the sky as possible in different wavelengths at different depths and different kind of aspects and then provide that data in this enormous database that then any astronomer who has a question who has a theory wants to look for things can just pour through that data that's how you find the Motions of thousands of stars moving together through the Milky Way to tell you oh something merged in with us and you know a lot of the telescopes that I kind of obsess over ver Rubin uh Nancy Grace Roman uid these are surveys because now it really democratizes astronomy you don't have to write the perfect paper so that you get access to the telescope time on James web or whatever you just get good at database programming you pull the data that you need from the database and you're able to do science and this is as available to brand new grads who are coming out of University as it is to season professionals who can still look through the same data so uh more interviews are going to be happening on these kinds of of topics so so stay tuned for that now I've done plenty of other uh in interviews about surveys that I'm fascinated with so I'll link a couple of them here all right we'll see you next time

Channel: Fraser Cain

Views: 39,667

Keywords: universe today, fraser cain, space, astronomy, exoplanets, James Webb, jwst, James Webb space telescope, tess, Ariel space telescope

Id: RyEVmDH5Cdk

Length: 64min 49sec (3889 seconds)

Published: Tue May 14 2024