 Okay, welcome again to the July webinar of the NASA night sky network this month We welcome how love us into our webinar who will tell us a bit of the story about now That's the last one who's going to tell us about the Lucy mission to the Trojan Astros This is really really exciting and a little bit about how all of you can potentially Participate in the research that we're that they're doing but first here's Vivian white with an activity that you can use to engage Your audiences in the types of objects found in the solar system and how they're classified Hi everybody Welcome to the webinar. I just wanted to give you a heads up And show you a quick activity on sorting the solar system This is what we do as scientists all the time. We sort things according to their characteristics So if you've got the space rocks toolkit if you're one of the clubs that has qualified for that It's a fabulous toolkit with lots of great activities this is one of my favorite it's called sorting the solar system and One of the things that you do if you didn't get the toolkit I was gonna say you can download these online and I've got the Link in there a chat window right now But what you do with that is you ask your participants to sort a set of objects that you give them everything from What we know are asteroids to? Meteorites that have fallen to earth You sort them into categories according to common characteristics and they can look at the information on the back side So we've got very injured crater for example here and it tells them where it is what it's made of and How big it is and it often has things it has Examples of like earth compared to Jupiter for the earth card So it tells you about how big it is in comparison to some other things as well So they can look at that information on the back You want to emphasize that there are no wrong answers to categories that they're sorting into And they can sort them into as many categories as they wish this gives them practice being scientists so these are great for a demo table and When they finish it is really fun to ask them We used to ask them what series you pull out series So this is the old set of cards the ones that are online have been updated You'd say where does this one fall in this Very fuzzy object, but it's not so fuzzy anymore. We know what it looks like now So I use I had that for a second ago. You can't even use Pluto and Sharon anymore either I use eras which is in there as well Because that's something we haven't seen close up kind of like these Trojan asteroids. We're about to talk about So it helps us talk about how we as scientists categorize things I use this often when people talk about Pluto and Why it has changed categories, I think it's a really good question and a good way to bring up how science works So feel free to download it. You can print those yourself on a single-sided paper fold them in half and you have the cards made Thanks for listening. Yeah, thanks I think it's really interesting because it in a lot of ways this activity points out that classifying things in the solar system is not always easy. It's in Categories are not clean-cut lines between them. And so there's a lot of good to come from that So dr. Hal Levison is an institute institute researcher at the Southwest Research Institute His principal research interests are in the dynamics of astronomical objects Focusing on the formation and long-term behavior of solar system bodies His work studies the formation of both giant and terrestrial planets The dynamic behavior of comets and Kuiper belt objects the origin and stability of Trojan asteroids and the formation of satellites He is best known for his work on the early dynamic evolution of the outer solar system Dr. Levison is the principal investigator for the Lucy mission to study the Trojan asteroids. Please welcome Hal Levison Hi everyone, can you all hear me? Yep, we can hear you. Awesome It's an impressive group of people that you have on this list. I've been watching the chat room now, let me just see if I can get this technology to work and Show you my slides great, so I'm Hal Levison. I'm from the Southwest Research Institute in Boulder, Colorado And I'm going to talk to you today about this really cool mission called Lucy That is going to go and study a Population of small bodies we have yet to see that I think are Going to teach us about the history and formation of the outer solar system So I thought I'd start off just by giving you a little Tutorial about Sometimes there's a little agreat when you get started Are you still seeing the first slide we are Maybe close it out and I'm gonna start it again sharing and then reshare Let me try one other thing Modern technology is great until it doesn't work. This is true It works just moments ago There you go Okay, so I thought I'd start off just by giving you a little tutorial about how NASA runs It's planetary exploration missions. There's basically four types of missions that NASA does that NASA does right um the that these are sort of sorted in complexity and Costs from the top being the cheapest to the bottom being the most expensive The first three are what call are called PI led missions And this is a really clever idea in my view that NASA came up with Where what they do is put out a call to the scientific community and say Write a proposal tells what you want to do right do anything you want They're not trying to You know drive what the community thinks is good and they'll take the ideas and evaluate them And decide which ones to fly this allows them to actually do a survey of the scientific community Rather than deciding what they at the top what NASA should be doing with these missions So the simplex mission is the smallest. It's about 50 million dollars. This is actually a new program These are small sets. They're less than 400 pounds each and they launch a secondary payloads on other missions So far I don't have a list of objects of missions to tell you about because it's so new nothing yet It's flawed or flown The discovery is the next level up Lucy is a discovery mission at about a half a million dollars through development and what that means is that That cost cap is actually the maximum amount that we can spend Until we launch it doesn't include the launch vehicle and it doesn't include The science operation so Lucy for example all done when we're all through is going to cost something like 900 million dollars To put it all in perspective Discovery missions are open to all ideas and you can see a list of some of the missions that are part of the discovery program Historically then there's new frontiers, which is a little less than a billion dollars It's PI led but they actually that's actually decides the kind of science they want to do There's a list here in the slides just telling you The the kind of things that were in the last call New horizons that just flew by MU 69 Juno, which is an orbit around Jupiter and Osiris Rex Which is a studying the near-earth asteroid called they knew are all part of the new frontiers and then there's the big guys These are things that are directed by NASA Europa mission is one of those things Viking Voyager and there's no cost limit and no piazz. So this is actually the science being driven by NASA headquarters So I said Lucy is part of the discovery mission We're a little less than a billion dollars for the top entire life cycle cost It's a tour of the Trojan Asteroids Trojan Asteroids are objects that lead or follow Jupiter by about 60 degrees in the orbit here You can see this little animation the inner region are showing the four terrestrial planets The outer planet is Jupiter and you can see the known trojans and the way to think about these objects is that if you put An object either exactly 60 degrees before Jupiter or 60 degrees after The gravitational attraction of the Sun and Jupiter plus the centripetal force Due to the object moving around the Sun all cancel out So if you put something near that 60 degrees point, it's stable forever And so these objects that we see and these are real trojans you see being shown in this Animation these objects date from the beginning of the solar system and that's why they're interesting to me as Somebody who studies the history of the solar system. Anyway, I'll get into more of that in a few minutes Lucy's gonna launch in 2021. We're gonna do a rehearsal of a main belt asteroid in 2025 this is just set as a practice for us But it turns out this object is really cool in and of itself And I'll explain to you why in a little bit then we're gonna have five Encounters of Trojans going from 2027 to 2033. I'll be 76 years old when this mission is over Studying a total of six Trojans because one of these guys the last one is a binary. It's my favorite It's really cool. And again, I'll explain to you why it's such an interesting object in a couple minutes so You know NASA and not just NASA all the space agencies have spent a lot of effort Studying the small bodies in the solar system. And so I thought I'd explain to you why They're interesting as you know with said in the introduction My history is not with missions, but with theory. I'm a theorist to build planetary systems on Computers and basically my interest is trying to figure out how planets like the earth Got where they were and the one thing that came out of our study of planet formation in the last 25 Years or so is the understanding that planets if you'll excuse the pun don't form in a vacuum they form as part of the system of Objects that all grow together and they're sharing spit with one another all the time To form the planetary system that we see today So when I try to understand where the earth comes from I try to understand the system as a whole Which you can see right here Okay, what I have plotted here Along the horizontal axis is distance average distance from the Sun You call the semi-major axis in units of astronomical units where the earth is at one astronomical unit So you can see the earth sitting there in this plot The y-axis is eccentricity, which is a dynamical characteristic of an orbit around the Sun Right what which is basically says how out of round the orbit is so if you're in a circular orbit around the Sun like the earth your eccentricity is near zero and As the orbit becomes more and more elongated the eccentricity goes up Eventually getting the one and the reason why I just chose those parameters Is it because it really just spreads the entire planetary system out so you can see its structure and then The dots represent objects by their size so you can see clearly sticking out the A planets the four terrestials and the inside before giants on the outside Then between the terrestials and the giants are a population of small bodies Called the asteroid belt outside the orbit of Neptune is another population of small bodies Called the Kuiper belt and you can see the Trojans locked in the same orbit With Jupiter and the reason why these small bodies are so important is Although planets once they form they've evolved a lot just because of internal processes These small bodies were created during the planet formation process They were sculpted as the planets grew and moved around but if yet remained relatively unchanged since then So the really the fossils of planet formation indeed Lucy is named for the human ancestor fossil known as a Lucy and that's because We you know Lucy the fossil has told us a lot about how the human race has come to be And we think these small bodies are going to tell us just as much about how the earth and Planetary system came to be and so it's the importance of these small bodies that have led NASA in particular but other space agencies as well to concentrate a lot on Studying these small bodies here's just some and not even all of the missions that are either Recently or either flying or recently defunct in some cases and a couple that are new showing the NASA is really trying to cover this entire population of Small bodies and Lucy if you notice if you just took Lucy away No one would be studying the Trojans. And so that's the role. That's the niche that Lucy's plane Untangle the history of the solar system So I'm going to concentrate mainly on Trojans from now on and what Lucy is going to do And I put this first bullet in this slide to remind me to tell you that this is really a Mission of exploration I'm a theorist and you're going to hear a lot about what these objects are going to tell us about how the planetary system form But really we're going to a population that no one has ever seen close up before and Indeed if you look at that plot over to the right where the Trojans are Most of the other small body reservoirs in the solar system Can deliver small pieces of themselves to the earth in the form of meteorites So we can actually study a lot about these objects by just going up and pick Going out and sometimes picking up a rock Trojans because of the proximity to Jupiter are not supplying any meteorites to the earth and There and as a result they are totally unknown. We really don't know what to expect But having said that I'm going to go back to the fact that I'm a theorist, right and talk about why Trojans are interested And that's because the remnants of planet formation. I'm going to talk a little bit about that in a In a moment But one thing that one characteristic of them that came really as a surprise as we started studying them from the ground is That they're not a homogeneous population again If you look at that plot at the right when people started discovering and studying Trojans They figured they were just the remnants of the formation of Jupiter and as a result Expected them to all be the same and therefore it was a surprise That they're very different from one another and there's several ways to look at that I'm showing a couple on the slide The one I'm going to concentrate on is what's called their spectral type Which is basically saying their color not only color in the visible but color including the infrared and There's three basic types of objects colored objects in the Trojans what we call C D and P type objects C's are basically gray These are very very red some of them are actually redder than Mars and P's are somewhere halfway in between and if you look at the Trojans They're roughly half D's and half P's with a little bit of C's sort of sprinkled in That's going to become an important part of our story in a couple minutes another way of looking at it This this plot in the lower left, which it measures Reflectivity or albedo. This is the fraction of light hitting an object in a particular wavelength range that is reflected so the For example, if you look at this plot up in the visible Trojans are some of them are dark Right albedo's where they're reflecting something like 1340 percent Of the visible light hitting them to really really really really really dark Over on the left where something like 4% of the light is reflected That's darker than just about anything that you see in your everyday Life, it's really really dark and that diversity I think is telling us something about How the solar system formed and evolved and let me just go in a little bit About that and I hope these videos work over this internet connection So as I said Trojans are interesting because they witness firsthand the history of the solar system one explanation For why they're so different from one another Is that they actually formed in different locations in the solar system? I'm going to show you an example of a model that does this that's called the niece model named after the city in france um I You know, like I said, there are a lot of ideas like this I'm going to concentrate on this because I'm one of the authors of the niece model But it'll give you an idea of how we're all works. So you can imagine By the way, can you say guys see my pointer? Oh, you're all in mute. So um, yes, your pointer came through just fine. Awesome So you imagine a solar system which has the sun and then jupiter Saturn and in this case Neptune and Uranus all shoved into a very small area inside roughly 14 to 15 astronomical units from the sun And then imagine there's a disk of asteroids starting just outside the orbit of the outer oise giant extending out to around 30 au Where it stops? Remember Neptune currently is out here, right? And so we believe the solar system formed in a much more compact configuration for the giant planets And was surrounded by this disk of material and as things formed in this this they formed the very different Temperatures because they're further from the sun and you can imagine I just Made this up But you can imagine the gray objects forming closer to the sun and objects becoming progressively red As you move out throughout the disk ending with the reddest objects out near 30 au It turns out that you can put this system into a A computer and I'm actually going to show you the real Simulation in a couple of minutes And the system is remarkably stable It will sit around like this in the planets orbit for hundreds of millions of years But eventually the planetary system goes unstable Uranus and Neptune's orbits cross They get scattered in bounce off and I mean by bouncing off They gravitationally scatter off of the Saturn and Jupiter They go into this disk and the disk gets When I usually give a talk on the subject, I'll show a bowling ball Hitting bowling pains making a strike these things get scattered all over the solar system Most of the material gets thrown out of the solar system and this is currently floating around in the interstellar space But a very small fraction of them will get trapped in these Trojan swarms And the probability of them getting trapped is actually independent of where They form so you would expect the population ending up in the trojans to be a mixture Of all the stuff that formed throughout the disk. This gives us a unique opportunity to send one mission out study the trojans And learn about this entire region of space, which is now physically empty But the only way we can really take advantage of the fact that the trojans are there for us to study Is to develop a mission that can sample this in diversity and that's exactly what lucy is designed to do So before I talk about that, I just promise you I would show you a movie Of a real numerical calculation Of this instability. So what you see here are these Circles represent the orbits of the giant planets again jupiter saturn neptune and urinus surrounded by this disk of asteroids And i'm just going to run it for a while And you can see the gravitational because of the orbits becoming Excited the planets are tugging each other and making the orbits change slightly the solar system is doing that today That's not unusual But when we get about 700 million years don't blink Boom, so you go from a system that's very compact To the system we see today in only a couple million years it's quite a Fantastic event and the trojans really are witnesses to that particular event All right, so the way that we can cover this diversity Is because we found a truly amazing trajectory for lucy And so i'm going to spend a little bit of time talking about lucy's trajectory What you see here is a plot the blue circle shows the orbit of the earth the green circle shows the orbit of jupiter And the white dots represent our targets and of course the red dot is lucy We launch at a very low velocity which allows us To actually use a very small rocket and we launch into an orbit That basically has an orbital period of one year After one year we come back to the earth and what we're going to use is we're going to use Gravitational encounter it's a swing shot Between the earth and the spacecraft To increase the orbit size of the spacecraft So at the end of our first year we encounter the earth and we go into an orbit That's two years long Have another earth encounter and the the beauty of this Geometry is we can actually use earth Target our targets and then therefore the spacecraft itself Doesn't need to carry a lot of fuel After the second earth encounter we're going to be thrown out To jupiter distances on the way out We're going to Pass an asteroid call that we named after donald john hanson Who was the discoverer of the fossil lucy? Study that Come out Near the orbit of jupiter We're going to have four encounters In 18 months it's going to be busy And i'll talk about our targets in a minute By the way, you see when we turn around in that orbit We are now further away from the sun than any nasa spacecraft That is powered by solar sounds So we're going further than any spacecraft solar powered spacecraft in history at that point And now after our four encounters, we're going to do another orbit around the sun Fall back into the inner part of the solar system Have another encounter with the earth Which is going to allow us target our last Trojan Encounter nearby the name of patroclus. It's the binary in 2033 So I as I said right one of the things that we have to do to really make this meaningful is cover the diversity of objects in the solar system and I Pointed out that it's cd and p-type asteroids. So here are our targets These are artist's conceptions. The shades are actually determined Basically by looking at light curves of their variability from the earth with ground base and telescopes also HST occasionally So we're going to go to uribides, which is a c-type Palmae, which is p-type Lucas and worse, which were both d's and then in the trailing swarm. We're going to go by menonitius and Patroclus, which is a binary in 2033 So remember I showed you this plot showing albedo I'll explain it a little bit more on the on the vertical axis It's the fraction of light these objects reflect from the sun and the visible and on the y axis I'm sorry in the horizontal axis is visible on the vertical axis. It's in the infrared the blue dots represent All the known Trojans and the red shows our targets. So we're really covering the diversity that we need to I'm going to spend some time just talking about individual objects in this because it turns out We were lucky enough to be able to fly by objects That are worth flying by even if we were going by one Because they're interesting The first I'm going to talk about is our first encounter uribides, which is the only c-type asteroid in this group Uribides is interesting because it's the largest remnant of the only disruptive Collisional family in the Trojans and what I would mean by that is that every once in a while Asteroids will run into one another and when they run into each other They break up and the fragments go flying away ending up as new Asteroids in orbit around the sun And we can discover these families because the fragments move away from one another so slowly That if you look like they look at their orbits, their orbits all clump together And so we can look through the asteroid belt and the Trojans and find these what we call asteroid families We've never seen an object like this before even our studies of objects in the asteroid belt haven't gone by Collisional remnant before and this object therefore is going to tell us a lot About the collisional processes in the old early solar system. Remember the planets that we see grew from the collisional accretion of these objects and as a result looking at the The accretion process by studying this object is going to be really poor But one of the real To me the reason why this object Is so interesting is because it represents a mystery Because Euripides is a sea type asteroid. Remember I said the the gray outstrikes the other two are more redder And I also told you before They're really rare in the Trojans only about seven percent of Trojan asteroids Are sea types and a lot of those are members of this family So sea types are really rare in the Trojan storms So why is it that the only family we see is a collisional family And or the only family we see is a T sub type and I think there are two reasons for that Or two explanations that Lucy can test the first is that these red asteroids these D Objects are so fluffy and soft when they hit one another They just break up into basically dust and are gone And the other is that whatever makes these objects red whatever makes these D's is only skin deep And when we break them open and look inside We'll see seas and the observations we're planning to take with Lucy will directly answer that question The other This in this case system where I want to talk about like I keep saying this is why my favorite I really love this system is the patroclus ameninichis binary This is an amazing system because it's a system of two Asteroids that are almost exactly the same size. You can see I listed your sizes there In a nearly circular orbit around one another and they're tidally locked So they're keeping the same face towards one another just like the moon keeps the same face Towards the earth you can see an image of this system taken with hst And that's basically all we know about it And the reason why these objects are interesting although the rare in the inner part of the solar system They're actually quite common in the far outer reaches of the solar system And in particular when we look to a population that we call the cold classical kuiper belt Objects remember I showed you at the beginning of my talk the structure of the solar system And the kuiper belt is sort of this asteroid belt that's outside the orbit of neptune And there's a region of the kuiper belt, which we believe is totally unperturbed By the formation of the planets And when we look at this population and you can see some hst data taken and this of course new horizons flew by it At the beginning of the year and this is mu 69 you can see it here too Almost every object in this population is a near equal earth Equal mass binary And it's the most perturbed unperturbed region of the solar system So I think that what this is telling us is that when objects first form In the solar system they always form as binaries And the reason why they're so rare these kind of objects are so rare Is because planet formation is so violent that the binaries are torn apart If this is true, then this binary this patroclus benenitius binary is a leftover from that pristine And that's going to be really cool to see And I'm going to spend a little bit just talking about some of the weirdos particular I want to talk about lucas lucas is just very strange It's strange because it's very elongated It's almost twice as long as it is wide. So it's sort of shaped like a football And it but the thing that's very surprising. It's got a very long Rotational period its day is four hundred and forty six hours long And to show you how unusual that is I have this plot here showing rotation period as a function of size For six thousand asteroids Um, by the way, this horizontal line is real It shows that asteroids are actually rubble piles made of rock And if you spin them up too fast, they'll fly apart So the small objects are solid rocks But the big objects are all rubble piles and we know that because of this break But this is where lucas is all the way out here making it one of the longest rotational All having one of the longest days in the solar system Trying to understand why that's true is one of the things we want to do I personally think there's a satellite there that we'll discover when we get there But you won't know until we actually send the space back. So that'll be very exciting So let me end with my tour of our targets by talking about our main belt rehearsal Donald Joe Hansen So Donald Joe Hansen just turns out we are lucky to go buy this object and let me explain Why don't Joe Hansen is a member of What we another collisional family called the Aragoni family And it turns out for these families We can actually date them because if you look at this is distance from the sun This is how big they are the lower the number the bigger they are. So these are small guys It turns out objects will drift Due to radiation pressure from the sun and the smaller the object the more it drift So you can use this v-shape To actually date these families An arrogant gummy is actually incredibly young only about a hundred million years old So we're going to be going to one of the youngest asteroids in the solar system with lucy all right So let me talk a little bit about again, how we're covering diversity Our biggest object to smaller object. It's got a mass ratio of about 160 They also have very different collisional histories As I said, the binary is probably primordial Uh, uribities is the remnant of a collisional disruption And palm a is so small that it's probably a fragment So we're going to be able to cover all kind of collisional histories with lucy All right So let me tell you exactly what lucy is going to do in order to cover The amount of real estate we are the spacecraft has to be moving really fast As a result, these are flybys like new horizons was a Pluto or an emu 69 the whole encounter Um Almost 99 percent of the important science in our encounter is being taken within four hours of the encounter So lucy is going to be spending decades getting to where it's going and it's all going to be over very quickly So we're populating lucy with a series of instruments that are going to allow us to learn As much as we can as we go screaming by these targets In particular, we're going to be able to study the geology We're going to get surface colors. We're going to get compositions We're going to be able to measure the mass of these things because the spacecraft is going to be deflected a little bit due to the target's Mass and we're going to be able to measure that and that's going to be able to tell us the density and therefore we're going to get An idea of what the interior structures look like and we're going to look for satellites and rings And we're going to do this with the spacecraft and a set of instruments Actually that have what nasa likes to call high heritage Which means we built them all before and therefore the relatively Low risk our philosophy when we put lucy together was to take things That are well known We know they work and send them to places that no one's ever seen before And that's exactly what we're doing with lucy upper right is the spacecraft To put it in scale the high gaining tena is about Is two meters in diameter another way to look at this is tip to tip with these huge solar rays Remember I said we're going really far from the sun. So we need big solar rays from tip to tip. It's about 50 feet All the instruments are going to be on this platform, which we can move around as we go flying by And there are four instruments on the spacecraft We have a Long focal length relatively large telescope called lori Which is for high resolution Images and lori flu. This is an exact copy of an instrument that's on new horizons We have what we call the terminal tracking camera, which is again A black and white camera. This is wide field low resolution. We're using it Not only for science, but for navigation as well. This is the exact copy of an instrument that's on osaurus rex We have i'll go out to ralph and talk about ralph ralph is actually Two instruments of one. It's a color camera and plus the new infrared Spectrograph which will allow us to measure the chemical composition of our targets And then we have a thermal Spectrograph it's going to allow us to measure the surface temperature of our objects and therefore Figure out how grainy they are if you think about it a solid rock Will heat and cool very differently than a pile of sand will and so by measuring the temperature and how the temperature Particularly cools off as parts of the asteroid move from day to night We're going to be able to get information about the surface properties of our targets um So let me just i'm going to end i'm i i finished basically the science part But i thought you guys would be interested to know how we got to where we are and as i said nasa In these pi led missions Just puts out a call to the community and say Just propose to us any things that's consistent with our interest in Study studying and exploring the solar system We started work in march of 2014 We submitted a 250 page proposal the nasa in february 2015. Let me explain the nasa does this There's selection of multiple steps No one has The financial resources to actually be able to write a proposal proving the nasa That your ideas will work. So in this step one proposal that went in in february 2015 We essentially presented our science idea told nasa why it was interesting and then did What i would like to call although i'm sure the engineers would be really pissed off if they heard me call it this a lego Spacecraft where we take things that were done before when we say we take you know, we take The solar rays and stick them here. We take the instruments to stick them there Sort of like putting like a lego thing together But not really being able to do the work to prove that the instruments will all play nice with one another But we gave them enough detail that nasa could choose a bunch to be That could be selected for further study That selection happened in september of 2015 Of the 20 proposals submitted in step one five were selected for future study We got a little bit of money. I remember it's about six million dollars or three million dollars I said in this to go off and do a better job That allowed us to spend a year studying the engineering and developing the science better Um Where we at the end we submitted a roughly thousand page what we call concept study report to nasa Which happened in august 2016 and then we had a nine and a half hour um Oral exam basically by nasa called the site visit. This was the hardest thing i've ever done in my life. I think um in november 2016 Delivered a 20 minute talk to the lead scientists in nasa in december And then we were selected for flight in january 2017 and we're We're two months and two weeks From shipping the spacecraft To cape canaveral to be launched in october of 2021 So i'm going to just stop by putting lucy in a little bit of context Our understanding of terrestrial planet formation Has been revolutionized by the study of main belt asteroids and yet only eight Main belt asteroids have been studied to date Are using unmanned spacecraft lucy will study almost as many trojans six as opposed to eight That uh With what has has been done throughout the entire history of unmanned exploration the main belt all within one Discovery mission. So that's why I love lucy. So i'll stop there all right, well, that's really uh Fascinating it's it's amazing on how all of these things kind of work together To you know situate themselves, I guess and we have a couple of really interesting questions And steve has a couple of questions and i'm going to kind of lump them together here if I can So steve asks if the trojans were formed at the time of the primitive solar system How did they end up in a tiny slot of the entire solar system? Basically between jupiter and the sun? And also To kind of go on with that. Are they unique only to jupiter's orbit? So, I mean there's several answers to that right there are trojans around other planets Jupiter's is probably the largest Neptune has also a large population of trojans and mars has two I don't know why mars only has a small population, but there are two I believe there are only two martian trojans. So trojans The reason why they got trapped is during this evolution of the solar system is just by luck That disc that formed outside the planets if the niece model is right Was massive it contained Probably 25 30 earth masses of these things billions of them as a result when the planets started moving around And jupiter moved during that instability Some of the of these guys were just lucky enough if you call it luck To get trapped and those are the ones we see today All right So jeffrey asks whether or not the trojans are kind of fit into the same classification systems such as the main belt asteroids So like carbonaceous stony metallic things like that. Do you anticipate that those are? similar sorts of classifications Yeah That well, of course, we're not returning. It's not a sample return mission, right? So we're not going to be able to compare them directly to meteorites if you look at just their spectral colors the c D and p type asteroids. There are asteroids like that In the asteroid belt and so the connection between them And the meteorites Are a matter of some dispute But one thing that we hope to do for example is to ask the question Whether a c type asteroid and the trojans Look the same as a c type asteroid in the main asteroid belt That's one of the things we want to compare and series is a c type asteroid So we're going to be able to do that comparison with this mission address that question of how they all relate to one another all right so kind of um going along with that um I know one of the aspects of this is and you didn't really address it and Is this idea of occultations and we were discussing this a little bit before we started broadcasting earlier And so this seems to be an important aspect to this and so maybe you could Tell us a little bit about that sure so In order to get the clearest picture Of these objects we go flying by them. It's very useful to know their sizes And they're rough shapes So as part of the lucy mission We have an extensive program of Occultation studies where we're sending um What we have this we inherited from new horizons, which did the same with mu 69 we have a um I'm gonna call them a fleet for for lack of a better word of on 16 inch telescopes That are all portable That we ship all over the world to get occultations of our Targets so that we'll know their shape and we do observations in the u.s. We've had a couple in texas one in arizona This november we're going to Australia to study oris and then about six months after that We have a couple trips to africa In order to be able to study our smallest object pollinate So this is something that's ongoing and it's an important aspect of what we do All right, so yeah Yeah, thank you And so I think that there might be some people that would be potentially interested in that and so maybe we'll um um Look on the lucy website and send an email to Our webmaster. There's a contact page If you're interested in participating and we can put you in contact With the people that are actually doing this. All right fantastic So linda notes that this is a fantastic presentation. She really enjoyed it And ask will the data collection be done by pre-programmed computers? And will there be any real-time control of the spacecraft and instruments during any of the flybyes? Absolutely not. We are good. This spacecraft is going to be totally autonomous. Matter of fact It's not even going to be in contact with the earth as we're flying by So we are going to plan these encounters beforehand We'll probably have them all in the bag particularly for the four that happen right away We're going to do four encounters in 18 months Right, it's no one's going to sleep on the team because it's so much work to get done But that's so one way to alleviate the amount of work is do all the planning beforehand The science sequence is going to be uploaded to the spacecraft Several months before the encounters and then we're just going to close our eyes and hold our breath And wait for the spacecraft to come back into contact with earth After the encounter to tell us that it's arrived and start sending back the data Um, we're actually going to be pretty far from the earth So we'll take months to download all the data that we collect But we do have a special a list of special observations Which should come down in the first 24 to 48 hours That will allow us to at least tell you right through press releases and things like that What these things actually look like All right So we have a couple of questions here about the composition of these dan I'm going to kind of lump these together and so dan wondered if maybe the red trojans are iron rich bodies and then issy was wondering You know the cd and p types are you know, what do you think that they're made of based on the data that you have collected so far so The interesting thing about these objects is that when you look at them From the ground at least you don't see any Spectral signatures to let you know what they're made of We believe just by running experiments in the lab And comparing them what we see from the telescopes that these the redness is due to organic material on the surface That have been radiated by the sun for long periods of time and These organic materials probably form from ice Which is why the further you get from the solar system the redder these objects get Right on when you're in the air part of the solar system The ice is when i'm mean by ice is all sorts of ice not just water ice Right, um evaporate from the surface too soon For them to be turned in or organics, but if you go further from the sun They hang around on the surface of the objects and therefore can be chemically altered By solar radiation and we think that's what the red Stuff is so it's probably just the organic gunk but there We should be able to see signatures of that Are the spectral range of our Ralph instrument or our Near infrared instrument was chosen to be able to see Very thick faint organic features on the surface of these bodies So do the what what do the cdp? Uh designation stand for do they mean do they stand for something? It just is a historical thing people started just taking specter of these objects and started just saying linking them together this one looks like this one and this one looks like this one and People started when we need to have names and they just started naming them in the order that they were finding them And so these letters really don't mean very much In and of themselves, but if you see two different classifications You know these things are different and you can look on the web And actually see what these colors look like If you want there are websites dedicated to that Okay, well, I think that we have time for one more question here And so john mentions this is uh something about the magnitude that uh that you're thinking here He said one of your slides mentioned absolute magnitude the distance scale for absolute magnitude of solar system Bodies is that different than that used for stars? absolutely, but it's It's a similar idea right it's the brightness of an object seeing um I must admit I don't remember the scale of this, but it's the brightness of the object Of an object. That's one astronomical uh Unit from the sun and one astronomical unit from the earth seen at the uh at zero phase But you know it scales in a similar way of being logarithmic In brightness or in flux right and the smaller numbers are actually the brighter things So put in perspective Um Actually that never mind. I was going to talk about apparent magnitude not absolute magnitude, but um Yeah, so that's it Well, this is really great. And so I'm really looking forward to uh, you know Seeing the the spacecraft get completed and get launched and go out there as you are too and and uh, this is a really exciting mission and and um, you know, I In some ways for me It was one of those mystery missions that you kind of hear these things about there. There was one called lucy And you really don't quite know what it is, but uh, thank you very much for I'm glad to help and you all should come down to Cape Canaveral On october 16th of 2021 And watch us launch. It's going to be a great show If you've never been to a launch it really is something to experience even these small rockets Are quite spectacular to watch All right And that's all for tonight everyone. Um, thank you dr. Leveson for joining us this evening and thank you everyone for tuning in I'm going to turn off the recordings My pleasure