Exploring the outer Solar System: now in vivid colour - Michele Bannister (SETI Talks)

welcome everyone to this week's SETI Institute seminar Dave very fortunate to have banister with our speaker Michelle did our under added work a cretin Christ Church in New Zealand then went to a and you in Canberra for her PhD observational astronomy she's just finishing up a postdoc at u Victoria in British Columbia and in a couple of months we'll be starting over at Queen's University and Belfast as research scientist working primarily on surveys of objects in the outer solar system which is what you'll be talking about today thank you very much Michael so today I'd like to tell you a little bit about the efforts that are underway with researchers centred in Victoria in cap in Canada in Taiwan in and here in the United States as well as across Europe in a collaboration who are working to understand the structure of the outer solar system I'm going to spend a little bit of time on the discoveries that were made to date and also how we're being able to use this discovery sample and the way in which we're discovering them to constrain the history of our own solar system and then at the end I'm gonna touch a little on some ongoing work we have to look at the physical properties of these objects what there is on the surface of them the thing we're really trying to find out by studying the worlds of the outer solar system is the history of our own solar system backyard how did the solar system come to be the way that we see it today the ice giant planets Uranus and Neptune that you see here in beautiful presence seen by one of our spacecraft some years ago now I have sculpted these their orbits and the current locations in space of these small worlds in the outer solar system there's hundreds of thousands of them left there today but they're just a fraction of what was originally present and the way in which we can look at the outer solar system to reconstruct this history this migration that has taken place of these big ice giants is we find what is there today and then we numerically simular how the migration of these ice giants could have led to the solar system as we see it today and the way we can do that is with simulations like this one by Rodney Gomez so here we have the solar system seen in an orbital parameter space so across here we have the semi-major axis of the shape of the orbit so there's the size of that the eccentricity of the orbit how much it's distorted from being a perfect circle and the inclination of the orbit how much it's tilted with respect to the plane of the solar system and you can see here this kind of green band this set of little dots this is at the start of the simulation many hundreds if not thousands of test particles of little objects where you're not worrying too much about what mess they are but their traces of what's happening how they're being dynamically moved as giant planets move in their migration this is the great discovery of the last decade or so of outer solar system work the solar system as we see it today is not the way that it formed it's when I run this you'll see at the top there T equals zero point zero million years we're going to run this forward with the giant planets influencing their gravity over time the initial quiet disk is completely disrupted by planetary migration the green dots the particles are scattered up they moved out and as Neptune moves outward you end up shoving a whole bunch of particles into this very dynamically excited state and you end up with a solar system where if I just pause it a little you have lost a large amount of material so the present solar system is but a shadow of its form itself it's a remnant fraction of the initial amount of mass several Earth masses indeed of a material that was in this planetary small disk and you also end up with objects being located very particularly in orbital parameter space you end up with different popular Asians as a result some of them will be where these blue lines are here in resonances with Neptune mean motion resonances and this just means when Neptune goes around the Sun an integer number of times they also go around the Sun and integer number of times yes the two-to-one resonance the three - two resonance and many many higher-order resonances because not having more giant planets out beyond here means you can get a filigree of resonance structure where Neptune is dominating what's captured into these little spaces of parameter space they're actually more kind of funnels on this than lights but it gets a it's a filigree it's it's really quite detailed so the takeaway from what happens as a result of this migration is most of the objects are gone a few of them are left in these captured into these resonances but resonances occupy a very small amount of the available parameters space they're tiny and yet today we see quite a large number of objects captured into these this is one of the big signatures that something has taken place to change the structure from how it formed to how we see it today it's really hard to end up in this resonance unless you are pushed around by the gravitational movement of a giant planet if we now move to have a look top-down on the solar system so going out here you know our part of the solar system is right closer 20a you further out in astronomical units 20 40 60 astronomical units you can see there euros NASA Neptune me I strand planet so it's referring to earlier and you can also see the grey dots of a particular population now this is a model of the population there are many hundreds of thousands of objects in this particular population and this is one sub population one resonant population of these ones I was telling you about this is the water known as the plutinos because Pluto is one of these objects and they occupy the three-to-two resonance with Neptune to understand how we can find these signatures of past migration there's a number of things that have to come into play in terms of where you look on the sky where they distributed around the solar system and how orbital dynamics forces them to be grouped on the sky as we see them from Earth so Pluto and Neptune over here this is kind of where the Galactic plane sits on the sky at the moment so this is an area where it's very hard to detect these objects because there are many dense stars and a small moving dot moving by lots and lots of stars is normally on top of a star so things here are kind of hard to find so okay you can see that's probably a place where you don't want to look to find these kinds of objects but these numbers around here are hours of right ascension hours of where you look on the sky to see these things at zenith at different times of the year and if I show you what happens if I was to take a large aperture telescope like the CEM defense Hawaii telescope which is one of the ones I use most and apply the fact that it's mirror four meters in diameter can only see objects that are so faint down to a particular magnitude that flux limit is what this does - what's observable about this population the ones to the up to the left and down to the right they're a God in that perspective they're simply not visible to the telescope and a four meter telescope for me to optical telescope it's a pretty big telescope it's still one of the biggest telescopes in the world that you can use for this kind of search this is just one way in which to the discovery of objects in the outer solar system can have a bias introduced on earth that's a flux bias another one is going to be a pointing bias if I look over here which this time of year 14 to 16 hours this would be discovery of objects and April through about May I will see a in some region of this population then if I was to come over here around 22 hours to zero hours and look in the middle of some of Northern Hemisphere summer so when you choose to look at the sky at the part of the sky that's most observable for most of the night determines which objects you find then there's really insidious biases there's ephemeris or tracking bias when you find a solar system distant object it moves across the sky at a particular rate that tells you that it's very distant in the solar system but if you make an assumption about what orbits are on on the outer solar system and then change where you next look at it to find it again that is an assumption that you are making about what type of orbits it's on this is a subtle bias it's a tricky bias and it's only really overcome by looking at these objects very frequently to confirm that your initial assumption about what sort of orbit hats on is actually valid at the worst it can mean that you lose objects there are at the moment of the 1900 objects-- that are listed in the Minor Planet Center which is the clearinghouse reservoir for where objects discovered all around the world are kept it's the International Astronomical unions master list of what we know about the solar system it's 1900 barely a thousand our objects where you can say that we know their orbits with any certainty 16 percent of these objects orbits that are effectively endangered 17 percent are objects that are lost I could not point a telescope at them we know once that somebody saw them but we have no idea where they now are these are the effects of a femoris bias and finally you have detection bias which is the software that you use to extract moving objects from the data how good is that at finding objects and the way you can test that is by planting synthetic objects into your images and running your detection pipeline and testing how well it recovers that's more quantifiable but the terrible amount of of ephemeris tracking bias that you have means that if you're trying to do this kind of work where you want to say okay I found a sample of objects in the outer solar system what does this tell me about how the migration happened it's very very unreliable to just take the data set straight out of the Minor Planet Center every time you use the entire set of Minor Planet tear nose for the love of little kittens think about which surveys found all of these objects so what we're trying to do with this telescope that came to France Hawaii telescope and with this collaboration of scientists which is now about nearly 50 people it's called the outer solar system origin survey and we're trying to provide a very large sample of objects in the outer solar system where we know where they are we know what orbits they're on and we know what biases went into finding them we can give you all of the biases in a very precise way that allow people who say here's an idea about how this structure came to be we can statistically test it against the detected sample and see how well we can constrain the orbital structure we do this by observing with a particularly high resolution cadence for these kinds of surveys so rather than discovering this object submitting it to the Minor Planet Center and then maybe looking again it has in a couple of years we observe the objects that we find at least twice every time that the moon is dark so every dark time the CF HT is pointing at our targets to try and recover them and extend the arc as these things well as the earth goes around the Sun and as these up much more distant objects move along the tiny amounts of their act that they move during the time we're looking and because we're able to do this we can end up with orbits that are exceedingly well and stood we can say if they're in resonance with Neptune or not after a tiny fraction of a percent of these things that take the better part of a thousand years to go around the Sun so on the left here I have orbital quality the precision to which we know the semi-major axis of the orbits of these objects and this is the increasing time that we've been tracking them for so after only two years we end up with better than ninety percent of our sample being orbital II secured to the point that we can say it is in a resonance with Neptune or it is not this is unprecedented this is if you take a whole bunch of objects from the Minor Planet Center you do not have this level of quality so this is the power of a characterized survey where you can say here is a sample that is very well orbitally understood part of the reason that we're able to get the orbits this good is that we pay an awful lot of attention to where the stars are so a outer solar system object is moving across the sky slowly but it still moves across the sky several degrees in the course of a year if you measure the if you produce an astro metric catalog if you know where the background stars are very precisely you can measure the movement of that moving object also very precisely so the residuals that we have on all of the measurements of these pianos are better than 0.1 arc seconds which is a significant improvement on the last such major survey that was made the Ken de France ecliptic plane survey and Steven Gwynn at the Canadian astronomy data center as the person who's really been putting the time and to make this possible in Star Trek he would basically be our head of estra matrix so at this point with we started the survey in 2013 and we run through 2016 so this is where we are in terms of discoveries we're now we have past the deep ecliptic survey which ran in the mid 2000s as the largest fully tracked sample of tinos ever does I said there were about a thousand that you could reliably say yes we can point another telescope at these and find them again yeah we have 440 new tear knows where we can say exactly where they are in most cases to better than the precision of the distance from the earth to the moon something that's 40 astronomical units away we can say where it is to within a lunar distance or better this is with about let's see that yeah that number is with with six eighths of the survey currently being processed so we still have a quarter of the survey left to pull the discoveries out of so we'll probably easily pass 500 discoveries of Tia notes so we're adding you know a mixture of 50% to the number of T nos that we can use but more than that we're providing the sample in a way that we know all of the biases about it so let me walk you through this diagram again there's the platino is just in the background in grey but the blue dots are just general different sorts of Tia knows the orange the orange diamonds here are the objects that we've found that are plutinos so this gives you some idea also of how our discoveries match the model of how blue Tino's come to their closest points and relative to the Sun they avoid Neptune because that's how our resonance works it's a protected region and we're targeting regions of sky where you expect to get these where these plutinos are close and when they're close they're bright and when they're bright they're within our magnitude limit and we can detect them and because we can detect them when they're close and bright we can see very small objects because the other thing to remember about trans-neptunian objects is they have very steep what's known as size distributions which is how many objects you have of each size you have very few big ones and a very large amount of very little ones it's like in the ocean there are a few whales and a lot little fish exactly the same thing in the outer solar system so what I have plotted on here is currently 378 of our discoveries and this area of sky here which I'm currently reducing pushes us over 400 so yeah this is this is pretty spectacular this is the kind of sample and the survey biases that come with it that you can use to really transform our understanding of how Neptune's migration happened what was existing in the early solar system and answer questions like it's a number of planets that we have in the solar system today the same as the number that it started with so I'm going to take you through this and two areas where we've really been able to start placing constraints on the deep structure of the outer solar system and yes the first of these is the deep structure in the Kuiper belt the highest density region of the solar system that we can see in this range and also I have to admit this is really interesting time there's a lot of dynamical interest in what's happening in the most eccentric of these more distant objects which our survey is not hugely sensitive to but we can place as I'll show you some interesting constraints I want to start off by only talking about a relatively small subset of our discoveries because the thing here is even with a small set of discoveries because we know all of the biases that went into making this survey we can place very strong constraints on the structure of the underlying population that was that must exist we're seeing the tip of the iceberg of this much larger population so here is the dense core of the Kuiper belt so 30 astronomical units and here going out to 85 again eccentricity of their orbit up to the point that you see in the central Kuiper belt and again inclination things are relatively low inclination and there's these two major resonances Neptunes the 3-2 truth the blue tea nose and the more distant two-to-one resonance the reason and objects are talked about in cat Volks paper which is submitted and should be on the archive very soon and the objects that have been dynamically scattered by Neptune are talked about in Cori shaman's paper which you can find on the archives there with even a small sample like this and you can see the blue dots here of objects that are not in resonance with Neptune that just sit in this region of orbital parameter space we've been able to statistically we've been able to not reject to use the correct terminology for we've been able to show that the classical belt has three components to it now having two components was has been talked about for a long time you have this dynamically excited Potter population now this isn't temperature I'm talking about not thermal temperature it's how much Neptune has thrown things around you have a dynamically much more excited hot population high inclinations high centricity z-- and you have this belt of very low inclination low into centricity very quiet sand orbits they just go round and round smoothly and stay very stable together you have some self gravitation that shuffles them around but for the most part they've never been disturbed by migration and if I cast your mind back to the simulation I showed earlier though that's kind of hard to keep in these migration scenarios you tend to dynamically kick things out and excite them which is very consistent with the hot population but it makes it a lot harder to conform the cold population so that provides a really interesting constraint on how you can do this migration maybe you can't just do it if Neptune is the only thing in the solar system in particular one of the things that becomes really tricky to explain from a migration viewpoint is the substructure in the middle of the lowest inclination part of the belt in the cold belt which we're terming the kernel it's very dense it's very confined in orbital parameter space both in semi-major axis and eccentricity and inclination and also in another orbital parameter which is the closest approach to the Sun the perihelion distance all of these parameters confine this dense population of Kuiper belt objects these objects have to be somehow produced by a migration scenario now there's a couple of these that have been proved produced konstantin batygin actually suggested you can do it by precessing Neptune's orbit quite fast as you migrate it with his courses and more recently David News Varney has suggested that you can produce this kernel as a result of when you migrate Neptune relatively smoothly at one point you actually make it jump the way that you can make it jump is that you have a fifth planet in the solar system you have another ice giant like you're in a sauna empty tomb that is ejected from the system during a dynamical interaction with one of the giant planets and as part of that dynamical ejection you end up moving Neptune's orbit relatively abruptly and that abrupt movement allows objects that at one time were in the two-to-one resonance which wasn't where it is now it was somewhere back over here to suddenly be left behind as a little fossil population and then the tooter one is shoved out across to its present-day location these are very testable kinds of scenarios because they require very particular imprints of the population to exist but because we have a characterized survey we can say alright your model predicts that the population should look like this if we apply the biases that we know that the survey had because we measured all of them very carefully to your prediction that's your predicted theoretical sample of what our survey should find well we just saw happened have the sample of what our survey did find you statistically compare them and you can either keep or reject the theoretical prediction the theoretical model of how this is formed so this is what you can end yeah you can find our discussion of how we actually confirm the existence of this kernel beyond a doubt in that paper which is currently on the archive there's another interesting population that exists so this is what that same region looks like once I start putting in more of the survey because it's an ongoing survey so we end up with discoveries accumulating through time you end up with that same very dense region in the middle of the classical belt here the red points are showing you what's in resonance with Neptune and how even something that looks like it's in the middle here you need to know its orbital parameters very precisely because that object can actually end up being in a higher order resonance with Neptune like here this is a seven to four resonance it's not the kind of thing that you necessarily think of a lot but there's a whole bunch of these higher-order resonances most of them extend well beyond the classical belt but what we've been able to find with the survey is that there's actually some blue objects here which are beyond the edge of what was thought to be the terminal resonance of the Kuiper belt the two-to-one resonance this is hard to explain these objects have been suggested before there was one or two of them are being found actually since I think the first one was about 2000 or so and that's kind of been one every five years popped up ever since so at the moment about three were known outside of our survey we found another two but the problem was without finding them in a survey where you can make these kinds of statistical tests you could just argue that one of the dynamically excited hot population objects was somehow dropped into a lower orbit here there it was actually from a more dynamically excited population you're just seeing one okay what does that tell you we can make the statistical test to assert that these objects that have been stirred out between beyond the tutor one and definitely members of the cold classical population which implies that the cold classical's were actually extending beyond the tutor one and make a diffuse disk going out further and it has to be no further than 60 au we can place again statistical constraints that it can extend past there but we can also say that it has to go out to at least 50 astronomical units and what we're implying from this is that Neptune's migration actually pushed objects out just a little further as well it's it's another constraint on the how Neptune had to move so I've shown you a little bit about the kinds of detail we can get in the densest part of the Kuiper belt where we can see a whole lot of objects enough you know that at this point you're kind of seeing much more you're seeing so many objects now as you know hundreds of these in this region that we're almost starting to see the true structure of the kind built without needing to model it it's it's really quite wonderful to see it come out in front of your eyes like this but I'm going to change tech and go a little further out right here here we have again the solar system in top-down view but at the top up here on the right there's a little circle in the middle and I think I can do this with the pointer there we go this little black circle up here is the orbit of Neptune so I've been working within 10 astronomical units of Neptune's orbit and what I've been showing you just now we're going way further out this is the the outermost part of the of the region influenced by Neptune we're not in the Oort cloud the Oort cloud starts in the 50,000 astronomical unit region and here I'm going out to about a thousand or so beyond about two thousand is where the tides from the other stars in the galaxies start influencing the orbits of these objects so we're not at that regime instead when a regime where objects could be influenced by Neptune and some of them are some of them are scattering objects their objects with large semi-major axes high centricity x' and they're perturbed by neptune on a relatively regular basis but they intrude into this quite large semi major axis region but there's also even stranger objects and I have a set of them here on this plot these are the objects that are detached from Neptune that cannot be perturbed by Neptune in the current day solar system they are isolated Sedna is probably the most famous example which you can see there with the green dashed line their closest approach to the Sun there piri Helia is lifted so high away from Neptune's orbit that they cannot be placed in they are fossils from some other configuration of the solar system now this has got really exciting recently because we're starting to get enough of these objects discovered that discussion of them has been ongoing for the last decade around 2002 2004 there were a couple of papers by Gladman and chen going okay does this mean we're getting these high eccentricity high perihelion orbits does this mean that we're starting to see evidence for a rogue planet in the outer solar system are the ones that we have now in the inner solar system well is this you know something out here and whenever you say there is something out here this is a always this is an this is a statement with a long history people have been going is there a planet well in those days it was a Planet X is there a Planet X in the outer solar system so it's not like lemon and chin were the first but then when Shepherd and true hero found 2012 VP 1 month 3 which you can see there with the solid red line which has you know that orbit looks kind of round at least on this projection then they started being talk and they proposed in their in their paper that the a little bit of that object would need to be formed by a giant planet in the outer solar system now giant in this case is not particularly giant with we know that the outer solar system should have a bunch of dwarf planets in it this is inherent in the way that you scatter a bunch of stuff out from the inner solar system so there should be some Pluto's and some heiresses and maybe some very small Mars small on the small end of Mars sized objects in the outer solar system what we're talking about here is something more on what people would go planet we're talking on the Earth's mass argument and so the question is how many earth masses and if you put it there is it going to make a signature on all of the closer in stuff in a way that would be detectable so one of the things we can do with our survey is we can place these kinds of constraints because you have scattering population which are dynamically interacting with Neptune and going out into the semi major axis regime where they would be turned on gravitationally by any such planet and so we are able at the moment there are a bunch of numerical simulations running which will be able to say is there is the scattering population as would be produced by a solar system with a giant planet in them consistent with the Osso sample at the moment when it's not very consistent it really really isn't which is but we're still doing one last final check before we go for publication so I haven't put that plot up for you what I can show you though is this object here in the blue which we discovered which is a weird one it has a relatively high perihelion as you can see it's relatively comparable with the other high perihelion high semi-major axis high centricity detached objects it goes considerably further out if there was a giant planet of the sort proposed by the target and brown and their paper a couple of months ago it would be strongly influenced by its Alban and the other interesting thing is proposed by Renu Mehrotra and kept Folker and courses in the paper but went on the archive yesterday this is up-to-the-minute stuff folks is that a lot of these objects are actually would be in mean motion resonances in the same way I've been telling you about mean motion resonances with Neptune for the inner solace in the for the Kuiper belt these kinds of objects turn out to be in mean motion resonances with proposed scenarios for a relatively similar thouest giant planet and this part of the outer solar system these are great these are fascinating scenarios for how our solar system looks and we have the data set that can provide the testing for exactly which one of these is correct whether it's the self gravitation that Ann Marie Madigan suggested when she visited here a couple of weeks ago or whether it's you know as cat and renewal suggesting or whether it's as Mike and Constantine are suggesting there's all these ways that you could produce this very strange set of orbits at this point I'll switch tack away from the dynamical situation that we're seeing and I'll go into a little bit of what we can tell you physically about some of these objects because I'm showing you plots on a on a graph of orbital parameters here because these objects are points of light they are not resolved we have a single pixel across them I do not make pretty astronomical pictures of lovely galaxies nebulae but what we can say with those with the color of those single pixels of light is that they can tell you about the surface competition compositions of these small very distant icy worlds and when we have a large program on these two facilities predominantly on the Gemini telescope here on Mauna Kea but also with observations from the Ken de France Hawaii telescope as you can see their neighbors on the summit ridge of Mauna Kea and this program with which is another one of these big international collaborations we have people from Queen's University Belfast from Taiwan from Canada several from the US a number from France but this is how these kinds of programs need to work you need the expertise from a whole bunch of people around the world the reason we're using both of these telescopes is that we're having to look at the reflectance spectrum what these objects reflect in different wavelengths and the normalized reflectance that you get in particular spectral bands whether it's the ultraviolet like you see here at the left towards you point three microns through bands known as G and R with more in the optical colors across to the infrared J band here they're near infrared so different materials on the surface of these objects will produce different absorption bands but very few of these objects are you going to see a pure signature of a single material surfaces don't really work that way you have a complex melange of stuff all jumbled up together and it's going to result in deeper absorption at some wavelengths than others and you can't just add more light and pull out a spectrum of these things they're just unfortunately to fate well it seems like this would be a relatively easy problem but the problem is also small tierno's rotate and they rotate relatively fast so here's a perfectly typical platino and it spins about every seven or eight hours this is pretty typical for the kinds of objects that we're discovering with the outer solar system origins survey because of this if you observe it one night in one color and then you come back the next night and observe a different color we don't have enough information after we discover the objects to tell you which of these kinds of rotational light curves is appropriate for each object that requires a big investment of telescope time and it can be done and it can be done very efficiently but that's a completely different science question to ask so instead what we do is simultaneous observing while Gemini is looking in the optical and the near-infrared can de France Hawaii telescope in the smell the lovely picture by joy Paul out of Gemini is simultaneously looking at the same icy world and that get picks up the ultraviolet and that lets us simultaneously find out which part of the surface the same part of the surface is facing towards the telescopes and we're able to make that measurement securely this means that the sample that we're building which will be about 120 plus objects when we're done which nearly doubles which adds again another 50% of the number of trans depth Union objects known with precise color information it removes one of the major variables and trying to understand these surfaces a lot of the times you end up with the measurements being made too far apart to be sure that it doesn't just mottled surface or rotational like her variation that's actually affecting your understanding the reason we want to get these physical properties so ties back again to how these things move in the solar system actually no I do want to show you this one first this one gives you some idea of the precision of measurements that were able to make so across this axis here is the optical color so the color in green in G bed and the color in red in our bed and on this axis you have the color in red and the color and J in the near-infrared so this is kind of your near-infrared color and this is your optical color and the symbols here correspond with optical properties sorry correspond with orbital families so over here where this big yellow star is you have the solar color that's if you just head in the sunlight bouncing traveling out to the outer solar system bouncing straight back to you that's exactly what it would be and so the different colors here show you how the material of the surface modifiers that solar spectrum responds over here this little fit is the how mayor family they're known to be covered in pure water ice so they have a very close to solar spectrum in that sense and you can see we have one object here which is a mcli excitable which may very well be a how may a family member because it's very close to being very consistent with that population you do see a gradient in color across the across the range of optical colors and you see some clustering in that dynamically excited objects tinge towards the blue end of the spectrum and over here objects in that population of low eccentricity low level excitation tend to be much redder this was already not this is that part is not a new finding but we can with measurements of this precision we're able to tease apart the interaction between color and dynamics color in some way corresponds to original location and the planetesimals plus subsequent surface processing it's a complex imprint that corresponds to how you form materials from an initial planetesimals of ice and dust and and organic gooey compounds as in coalesced into planetesimals that we then measure in the present day so when the sample is complete we'll be able to make one of the I think the best assessments ever of how color how physical surface property relates to dynamical composition because the way we're choosing the sample is that we're making a complete sample every single object discovered by the outer solar system origin survey that incredibly precise knowledge about how it was found and how that relates to the underlying population of that dynamical type is being observed by this population if it's brighter than magnitude 23.5 in the optical bed so we're getting a really comprehensive sampling of high precision color from all across the different dynamical populations and this is exactly the kind of survey where you need to have a large comprehensive ground-based look at what's going on in these populations if you then want to send a spacecraft to it so New Horizons after it went past Pluto it's still traveling it will keep traveling without doing anything else for a very very very long time until it can no longer talk to us until we can no longer hear it's very very weak voice that won't be for the better part of 20 years yet but in only 2019 it will get to its next little target pass Pluto which currently is rather glorious new named well it was named Petey won but it now has a Minor Planet Center designation which i think is 2014 mu 69 we promise it's going to get a better name I'm pretty sure and so New Horizons in 2019 will be able to take pictures of the sort that it did at Pluto of one of these little worlds that I've been you know showing you the orbits of and this mysterious population of this thermal of objects the object it's going to is one of the ones from the kernel it's not one of the ones found by the outer solar system origin survey we don't look in the right part of the sky for them this object sits right in the middle of the galaxy so it was really hard to spot you needed the Hubble Space Telescope to be able to separate out the background stars away from this object and it will be able from the images it'll take when it goes past this world to tell us what's something that's about the size of Mountain View itself what it looks like up close and we'll be able to fit that understanding into the greater picture that we have from these kind of big ground-based surveys about the overall population what their composition is how that relates to the dynamical migration story it's the difference between you know getting to go and kick the rock and looking at it from a very very long way off so both of these things are necessary for understanding how the solar system came to be in its current form a ssin and it's in its current configuration but they're very complementary so to conclude outer solar system origins survey is now up to 400 new objects that are incredibly well known in space most of them I can tell you where they are to better than the distance between the earth and the moon and this is a really transformative sample for being able to tell us about how the solar system got to be the way that we see it today we're starting to see these new populations there's density of structure within the outer solar system and it's even starting to tell us a little bit about what might be even further out in the solar system where the objects that we see are just the tip of the iceberg we only see the brightest ones in the places that we happen to be looking and the color studies that are ongoing if you would like to see how we go with publications there's several up here already you can see a little more about it also survey org thank you very much we have plenty of time for questions I'll be running around with the microphone in some approximation of order I'm curious what limits the magnitudes that you can see was it 25 is that integration time so here is magnitude so this is bright at this end and this is going fainter at this end astronomers logarithmic magnitudes it's a pain so 24.5 is the limit of faintness that we can see with a four meter telescope staring at the sky for five minutes straight the reason we keep each image with the aperture so but the shutter open to only five minutes I like it sounds kind of short given you go okay why can't we keep it open all night we keep it to five minutes because we don't want the object to move across we're tracking at the rate the stars are moving so we don't want the object to differentially move across that too much and smear all its light out which point it actually gets fainter so our discovery efficiency and you can see here there's different symbols for different rates of motion things closer to us in the solar system so a Center at like the distance of Saturn also is in this lighter green 10 to 15 AK s/h motion range and we end up losing sensitivity to those slightly brighter than we would slower moving objects because they move off the edges of the telescope field of view more quickly so we'd lose a bit of efficiency there this is the efficiency that we can determine of how faint we can see for different distances in the solar system determined by putting about this one we put about 20,000 objects into our discovery images and then recovered them again we've actually improved that since then and now we do about a million hello over here so you had a slide that had like some things you might expect to see in the color spectrum methane water things like that with their various wavelength characteristics and I'm wondering you know basically where you got that list from and has the new as okay well that's good but has New Horizons examinations of Pluto and Charon and the smaller moons shed any light on what you might expect since 2004 on on those object surface characteristics yeah this has intended to be a representative list of materials that you that you could have I can make this you know there's the USGS this paper is a laboratory measurements of different materials of what their spectral profiles would be like across across these wavelength spans this kind of catalogue is far more extensive you expect to hear the kind of silicate minerals so your pyroxenes your olivines but of course you're gonna get you know potentially more complex other silicate minerals as well the trick is just pyroxene and olivine tend to be ones that are more likely to be found and have you know good good big thumb prints so you know you check for those first as well water ice is something you do expect to find as well you know you're in such a cold temperature regime around 50 Kelvin that it also depends how big the object is whether it's has enough self gravity to hang on to some of these materials that become volatile so methane for example is one we don't necessarily expect to find unless the object is relatively physically large but you would find it on something like Pluto which is big enough to have the gravity to hang on to that molecule long chain hydrocarbon on the other hand is the phrase I'm using and proxy of using the word stolen because what Solar means in different parts of the solar system is also tricky people talk about Titan tholins or Triton Solon's and the two big moons it's very complex organic chemistry and it's basic it's it's kind of amazing that you know you can take nitrogen ice and a bit of methane and under the cosmic bombardment of high-energy particles of cosmic rays you end up with this group and it's optically quite red but exactly what it is is very hard to work out and it can be a whole mix of different sorts of these hydrocarbons a Michel I'm sure you were expecting this question from me so you talked a lot about how you detect those tierno's you have the orbit the color but you don't I did not mention the multiplicity the existence of multiple asteroid system in the transient population yeah do you have a follow-up program for that so the Gemini data is the best way that we can tell if these objects are in fact binary so just for more context here the binary fraction that we expect is different in different dynamical populations so dynamical citation tends to break apart binary structures because most of the time we don't have contact by noise there's not a whole lot of contact binaries where the objects are physically nearly touching in the Kuiper belt but there are quite a lot of wide binaries and wide in this case is the semi-major axis is so large so many several tens of thousands of kilometers in some case that the little bit of the two objects is such that they're actually orbiting each other at walking pace really really slow fragile binaries and those are present in the coal classical population with gravitational movement of these objects has been very gentle if at all for our sample the CF HT data doesn't have the resolution to find binaries unless they're very wide so in the sample I've been showing you we have two wide binaries one of which was previously known and from the Gemini data which has a much higher pixel resolution because bigger aperture telescope we're seeing much higher binary fractions so we're seeing binary fractions that are entirely consistent with the HST surveys Hubble Space Telescope of the cold classical's honestly it gets to the point that it's like what isn't binary in the cold classical's it's really spectacular and it's a really interesting problem because how do you end up with a planetesimal formation mechanism if these things haven't been moved around where you've preferentially make binary systems so another thing that you can figure out about different populations is their size distribution and there have been claims that different subpopulations can different size distributions can you say anything about that and how it correlates with dynamics or colors yeah no that is a point that we have actually been planning to look at more now that we have the larger ensemble of data so the size distributions that we can look at we predominantly are focused on looking at them in the cold classical so I know kept Volks paper yes I think it did look at size distributions within the plutinos and also I think the five to twos in her paper she was finding that the size distributions on the 5/2 is such that it's actually the five two twos are much more numerous then formation model models had typically been predicting so example the nice model which is a popular one for rearranging the solar system does not predict the five to two size distribution that she found from our sample will be able to I think so the first quarter of the survey is public we didn't talk about size distributions and there will definitely talk about the classical population size distributions I should have that paper finished by the end of May I think I have a question about resonance and I can understand how for example with the moon and the earth that there's a one-to-one resonance that that the moon has a bulge on the Earth's side and that's held in place as it orbits the earth so that we're looking at the same side of the moon all the time but in the case of mercury orbiting the Sun or in your cases here you're talking about like two-to-one resonance three to two resonance and and that's what I don't understand is how the resonance how does gravity function to lock in those resonances main motion resonances are a yeah they're an interesting problem this is this is also an interesting inversion in the situation that you get like in the asteroid belt where mean motion resonances with Jupiter are actually more cleared of objects where they become unstable in the situation here where your exterior to Neptune the resonance becomes an region of orbital stability to be in so when your orbital parameters match and they can match because Neptune is migrating so it's actually pushing itself into the point that the object's orbital parameters our an integer value of what Neptune's are then you end up with a point at which both of these objects are orbiting where the little minor planet is protected from further gravitational and interaction with Neptune and at that point there can't be further scattering then it's safe they just keep going around in this nice little interlocking dance is it yeah it's a conservation of angular momentum so you end up actually distorting some of the orbital for other orbital parameters like eccentricity or inclination so that everything matches I can have a just a general question so can you comment anything on the color spectrum that you found in these are outer orbital regions compared to the color spectrum maybe that the human eye can see on earth have you found any have you guys been able to maybe create a new spectrum of color that's just for these planets and are they whole different are they than the color spectrum that the human eye can see on earth if you're looking at this with the human eye the ones that I'm kind of in this region your eye would see them as kind of gray and the ones over in this region your eye would kind of see them as maybe like orbiting I think it's probably a good analogy yeah they're relatively reddish you've talked about the many small Kuiper belt objects but in a recent talk on new horizons they talked about the problem of finding candidate objects to visit beyond Pluto and they said there were fewer small Kuiper belt objects that expected yeah they're probing a different regime of a different part of the size distribution than we can with this survey so because of the flax limit that we have we can only see some resin some resonant populations at their closest approach to the Sun so we can only probe down to objects that are maybe the same size as Mountain View and diameter whereas they're using Hubble Space Telescope and doing a very focused look at a very particular orbital population and so they can see down to objects that are smaller again okay if there are more questions please ask them michelle afterwards and thank you again you

Channel: SETI Institute

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Length: 58min 51sec (3531 seconds)

Published: Fri Mar 18 2016