{"version":"1.0.0","segments":[{"startTime":5.385,"endTime":10.635,"body":"One of the things I really want to get across in these Gresham lectures is"},{"startTime":10.635,"endTime":13.085,"body":"the many different ways that science happens."},{"startTime":13.555,"endTime":18.21,"body":"Sometimes, just occasionally it happens in the way you read about in books where somebody"},{"startTime":18.21,"endTime":22.245,"body":"comes up with an idea, designs an experiment, and goes and tests it."},{"startTime":22.585,"endTime":26.745,"body":"But a lot of the time things are more chaotic than that."},{"startTime":27.245,"endTime":29.305,"body":"Uh, I see a few nods in the audience."},{"startTime":29.405,"endTime":31.105,"body":"So clearly people ag agree."},{"startTime":31.445,"endTime":34.225,"body":"Um, sometimes science happens to us."},{"startTime":34.725,"endTime":40.105,"body":"Uh, things occur that change our view of, in this case, the universe."},{"startTime":40.445,"endTime":46.453,"body":"And that's the story of tonight's lecture, this, uh, small object UA that shot through"},{"startTime":46.453,"endTime":46.854,"body":"the solar system in 2017 and left us, uh, with new ideas and an awful"},{"startTime":46.854,"endTime":54.065,"body":"lot of new questions."},{"startTime":54.565,"endTime":55.625,"body":"Uh, uh, as well."},{"startTime":56.995,"endTime":61.163,"body":"The Gresham College lecture that you're listening to right now is giving you knowledge and"},{"startTime":61.163,"endTime":61.44,"body":"insight from one of the world's leading academic experts, making it takes a lot of"},{"startTime":61.44,"endTime":61.718,"body":"time, but because we want to encourage a love of learning, we think it's well"},{"startTime":61.718,"endTime":70.055,"body":"worth it."},{"startTime":70.915,"endTime":73.975,"body":"We never make you pay for lectures, although donations are needed."},{"startTime":74.435,"endTime":76.055,"body":"All we ask in return is this."},{"startTime":76.605,"endTime":78.895,"body":"Send a link to this lecture to someone you think would benefit."},{"startTime":79.235,"endTime":83.151,"body":"And if you haven't already, click the follow or subscribe button from wherever you are"},{"startTime":83.151,"endTime":83.935,"body":"listening right now."},{"startTime":84.995,"endTime":86.575,"body":"Now, let's get back to the lecture."},{"startTime":89.165,"endTime":94.724,"body":"Um, I did think I'd start though, uh, with some of the traditional form of"},{"startTime":94.724,"endTime":95.095,"body":"science, the very methodical, careful, uh, work carried out, for example, by people, uh, dressed"},{"startTime":95.095,"endTime":101.025,"body":"like this."},{"startTime":101.525,"endTime":106.093,"body":"Uh, this is the clean room at the Jet Propulsion Laboratory, and this is a"},{"startTime":106.093,"endTime":108.225,"body":"bunch of scientists trying to work out."},{"startTime":108.575,"endTime":113.136,"body":"Well, if you've ever had a problem getting a jam jar open, this is the"},{"startTime":113.136,"endTime":113.745,"body":"scientific equivalent."},{"startTime":113.975,"endTime":119.283,"body":"This, uh, spacecraft, that's what it is sitting in front of them, is the Azaris"},{"startTime":119.283,"endTime":119.636,"body":"Rex spacecraft, which journeyed to an asteroid called Benu, which is, uh, a near earth"},{"startTime":119.636,"endTime":124.945,"body":"asteroid."},{"startTime":124.965,"endTime":130.118,"body":"It crosses the Earth's orbit, and in fact, has, uh, the highest chance of any"},{"startTime":130.118,"endTime":134.585,"body":"large asteroid that we know about of hitting us in the foreseeable future."},{"startTime":135.045,"endTime":138.185,"body":"Uh, the foreseeable future being sometime in the 22nd century."},{"startTime":138.685,"endTime":142.903,"body":"Um, I don't think you have to worry at all until possibly the year 2080"},{"startTime":142.903,"endTime":143.185,"body":"something."},{"startTime":143.325,"endTime":147.145,"body":"So, um, looking at most of you, we are fine for now."},{"startTime":147.335,"endTime":149.825,"body":"Even I will be be long gone, I suspect."},{"startTime":150.205,"endTime":153.145,"body":"Um, but as Iix went to Benu, here it is."},{"startTime":153.145,"endTime":158.379,"body":"Here's a closeup of the asteroid, and on the right is this sampling tool that"},{"startTime":158.379,"endTime":163.265,"body":"was deployed to take samples from the asteroid and bring them back to Earth."},{"startTime":163.605,"endTime":165.985,"body":"And it was designed to work on a solid surface."},{"startTime":166.125,"endTime":170.646,"body":"But as you can see in a second, as it hit the surface of this"},{"startTime":170.646,"endTime":170.947,"body":"asteroid, it found basically, rather than a solid object, this body, which is a few"},{"startTime":170.947,"endTime":171.249,"body":"kilometers across, turned out to be a rubble pile, essentially about as structurally sound as"},{"startTime":171.249,"endTime":183.005,"body":"a sand castle that you might have built on the beach."},{"startTime":183.385,"endTime":184.725,"body":"Uh, and this caused problems."},{"startTime":184.865,"endTime":188.845,"body":"It did indeed manage to sample lots of the material and return it to earth."},{"startTime":188.845,"endTime":193.697,"body":"Here's the capsule sitting at the end of last year, uh, on the Utah desert,"},{"startTime":193.697,"endTime":196.285,"body":"looking brilliantly, like something out of science fiction."},{"startTime":196.865,"endTime":201.541,"body":"Um, but instead of getting a few large lumps, what they got was a pile"},{"startTime":201.541,"endTime":202.165,"body":"of rubble."},{"startTime":202.545,"endTime":205.205,"body":"And so there were good things about that."},{"startTime":205.665,"endTime":209.801,"body":"One of them was that even by scraping the outside of the collector, this is"},{"startTime":209.801,"endTime":210.077,"body":"the outside of that jam jar, you could see that there's dust and material on"},{"startTime":210.077,"endTime":214.765,"body":"the right there."},{"startTime":214.765,"endTime":219.253,"body":"They actually got 70 grams of material from the outside of the collector, which is"},{"startTime":219.253,"endTime":222.845,"body":"more than they were trying to get of the asteroid in total."},{"startTime":223.345,"endTime":227.533,"body":"Um, some of that material's now here in London at the Natural History Museum, it's"},{"startTime":227.533,"endTime":230.605,"body":"been distributed to scientists around the world who will study it."},{"startTime":230.985,"endTime":235.925,"body":"Um, but until yesterday, they hadn't managed to get into the collector itself."},{"startTime":235.925,"endTime":239.825,"body":"There was so much material it had jammed, uh, and, you know, they couldn't hit"},{"startTime":239.825,"endTime":240.085,"body":"it against the side or, you know, we've all done that and, and had things"},{"startTime":240.085,"endTime":244.245,"body":"go wrong."},{"startTime":244.265,"endTime":248.517,"body":"So they had to build special tools, but I wanted to celebrate them because yesterday"},{"startTime":248.517,"endTime":249.085,"body":"this happened."},{"startTime":249.515,"endTime":255.922,"body":"This is the inside, uh, and we now have this pristine asteroid sample, uh, here,"},{"startTime":255.922,"endTime":257.204,"body":"uh, on Earth."},{"startTime":257.625,"endTime":262.936,"body":"And about a third of this will be distributed to, um, labs around the world"},{"startTime":262.936,"endTime":263.645,"body":"for analysis."},{"startTime":263.705,"endTime":266.805,"body":"We want to understand Ben's composition."},{"startTime":266.945,"endTime":270.845,"body":"We might, after all want to divert it, uh, away from us one day."},{"startTime":271.225,"endTime":276.375,"body":"Um, but we're also interested because it's a pristine relic of a time about four"},{"startTime":276.375,"endTime":276.718,"body":"and a half billion years ago when the planets in our solar system were forming,"},{"startTime":276.718,"endTime":285.645,"body":"they may well have formed out of building blocks like this asteroid."},{"startTime":285.645,"endTime":291.221,"body":"And so as well as defending ourselves, um, we can learn, uh, from objects like"},{"startTime":291.221,"endTime":291.965,"body":"this one."},{"startTime":292.745,"endTime":294.925,"body":"Let me take those two ideas in turn."},{"startTime":295.285,"endTime":299.285,"body":"I think having mentioned that Benu might hit us, I should reassure you that we're"},{"startTime":299.285,"endTime":300.085,"body":"actually doing okay."},{"startTime":300.585,"endTime":305.462,"body":"In terms of planetary defense in particular, um, there have been many ideas about how"},{"startTime":305.462,"endTime":309.365,"body":"if we saw an asteroid coming towards us, what we might do."},{"startTime":309.395,"endTime":314.053,"body":"Some of them, for example, uh, in Hollywood films where they suggest for some reason"},{"startTime":314.053,"endTime":314.363,"body":"you send, um, Bruce Willis and a team of oil executives to blow it up,"},{"startTime":314.363,"endTime":320.885,"body":"that spoiler alert doesn't work very well."},{"startTime":321.185,"endTime":325.226,"body":"Uh, or another film where they just send Bruce Willis, uh, I dunno why it's"},{"startTime":325.226,"endTime":325.765,"body":"always him."},{"startTime":325.835,"endTime":327.845,"body":"He's clearly a, a clearly a specialist."},{"startTime":328.265,"endTime":332.165,"body":"Um, my favorite idea for years was that if you saw an asteroid coming towards"},{"startTime":332.165,"endTime":334.765,"body":"you, as you could see, this material is quite dark."},{"startTime":335.385,"endTime":339.885,"body":"Uh, it's, it's blackish and that's quite common, uh, for Nero asteroids."},{"startTime":339.905,"endTime":343.205,"body":"And so my favorite suggestion is you still send Bruce Willis."},{"startTime":343.825,"endTime":345.845,"body":"Uh, we wanna make sure he's still got a job."},{"startTime":346.145,"endTime":350.33,"body":"Um, but instead of blowing it up or attaching a rocket motor, all you do"},{"startTime":350.33,"endTime":351.725,"body":"is paint the asteroid white."},{"startTime":353.115,"endTime":357.685,"body":"That then changes the, uh, properties of the interaction of the, the asteroid in the"},{"startTime":357.685,"endTime":357.99,"body":"sun."},{"startTime":358.425,"endTime":360.285,"body":"Uh, it gets a change of momentum."},{"startTime":360.285,"endTime":363.922,"body":"And if you do that early enough, the asteroid will deflect and not hit the"},{"startTime":363.922,"endTime":364.165,"body":"earth."},{"startTime":364.625,"endTime":368.918,"body":"Uh, unfortunately, recent calculations say that you'd need to do it thousands of years ahead"},{"startTime":368.918,"endTime":372.925,"body":"of any impact, and we don't have the ability to predict that far ahead."},{"startTime":373.225,"endTime":375.405,"body":"So, uh, Bruce really is out of a job."},{"startTime":375.405,"endTime":377.805,"body":"What we could do instead, I is brute force."},{"startTime":377.905,"endTime":383.761,"body":"And this was demonstrated a couple of years ago by a mission called dart, which,"},{"startTime":383.761,"endTime":386.885,"body":"um, brutally attacked a small asteroid called Dimorphic."},{"startTime":386.885,"endTime":388.485,"body":"Dimorphic is the thing on the right here."},{"startTime":388.715,"endTime":392.245,"body":"This is a, a, a double asteroid, and they'll be important later."},{"startTime":392.595,"endTime":393.165,"body":"It's a binary."},{"startTime":393.195,"endTime":394.205,"body":"They go round each other."},{"startTime":394.225,"endTime":397.845,"body":"The large one's called didymo, uh, and the small one is dimorphic."},{"startTime":397.875,"endTime":399.925,"body":"It's a, a few hundred meters across."},{"startTime":400.665,"endTime":405.545,"body":"Um, and what DART did was take a spacecraft about the size of a mini,"},{"startTime":405.545,"endTime":409.125,"body":"um, and head directly for, uh, the smaller of the moons."},{"startTime":409.425,"endTime":415.975,"body":"And so these are images from the Dark probe, which was launched, uh, to impact"},{"startTime":415.975,"endTime":417.285,"body":"this small asteroid."},{"startTime":417.285,"endTime":419.125,"body":"This is really a test of technology."},{"startTime":419.195,"endTime":425.654,"body":"It's, can we, can the, the spacecraft steer itself accurately enough to hit this small"},{"startTime":425.654,"endTime":426.085,"body":"moon."},{"startTime":426.085,"endTime":428.285,"body":"As you can see, they look rather like better."},{"startTime":428.285,"endTime":433.965,"body":"It's this rubbery surface, uh, not really solid, but Dart scored an absolute bullseye."},{"startTime":434.255,"endTime":438.445,"body":"These are the last images that it sent back, um, as you can see."},{"startTime":438.465,"endTime":440.365,"body":"And then that's the last image that came back."},{"startTime":440.365,"endTime":446.268,"body":"We only got the top bit, and we had the strange experience of watching a"},{"startTime":446.268,"endTime":446.661,"body":"mission control full of scientists who built this spacecraft celebrating wildly as their craft destroyed"},{"startTime":446.661,"endTime":452.565,"body":"itself."},{"startTime":453.345,"endTime":457.165,"body":"Um, the reason that this was done, it seems slightly odd."},{"startTime":457.245,"endTime":461.625,"body":"I mean, okay, we want to show that we can hit the thing, but the"},{"startTime":461.625,"endTime":466.005,"body":"idea was also to show how much an impact like this can deflect the asteroid."},{"startTime":466.595,"endTime":470.556,"body":"That seems a bit odd After all, you know, I set questions for students that"},{"startTime":470.556,"endTime":472.405,"body":"say, okay, we've got two snooker balls."},{"startTime":472.405,"endTime":475.75,"body":"If I hit one snooker ball with another, if you know the mass of the"},{"startTime":475.75,"endTime":475.973,"body":"snooker balls, you can count the speed, you can calculate what's gonna happen to the"},{"startTime":475.973,"endTime":479.765,"body":"other snooker ball."},{"startTime":480.425,"endTime":482.605,"body":"I'm very, very good at snooker in theory."},{"startTime":483.145,"endTime":485.005,"body":"Uh, the practice I I leave to others."},{"startTime":485.385,"endTime":489.937,"body":"Um, however, because the asteroid is a rubble pile, when you hit it, it's not"},{"startTime":489.937,"endTime":492.365,"body":"like a solid ball hitting another solid ball."},{"startTime":492.365,"endTime":496.125,"body":"You get material thrown up into space, um, that can help you."},{"startTime":496.585,"endTime":499.805,"body":"Um, it can have a sort of rocket effect or it could hinder you."},{"startTime":500.225,"endTime":505.239,"body":"Um, and actually the impact of data into Dimorphic was much more spectacular than anyone"},{"startTime":505.239,"endTime":507.245,"body":"thought it was going to be."},{"startTime":507.785,"endTime":512.951,"body":"Um, the team were rather reluctant for people to go out and look with back"},{"startTime":512.951,"endTime":517.085,"body":"garden telescopes, but many of those who did saw the asteroid Brighton."},{"startTime":517.585,"endTime":522.268,"body":"Uh, and with the Hubble Space Telescope, we got this spectacular view of a long"},{"startTime":522.268,"endTime":523.205,"body":"tail of material."},{"startTime":523.275,"endTime":528.916,"body":"This is dust that's thrown up from the asteroid streaming through the solar system over"},{"startTime":528.916,"endTime":531.925,"body":"many thousands of kilometers for many months afterwards."},{"startTime":532.545,"endTime":537.328,"body":"And by studying the orbit of dimorphic around DIDs, the larger moon, we're able to"},{"startTime":537.328,"endTime":538.285,"body":"measure the deflection."},{"startTime":538.905,"endTime":540.925,"body":"And it turns out that we're pretty good at this."},{"startTime":541.065,"endTime":545.452,"body":"So if we'd seen an asteroid of this size, a few hundred meters coming towards"},{"startTime":545.452,"endTime":545.745,"body":"us, and we had 10 years notice, we'd be able to launch a copy of"},{"startTime":545.745,"endTime":552.765,"body":"Dart, uh, and deflect it and stop it hitting us."},{"startTime":553.385,"endTime":556.316,"body":"So the question is whether we'd have 10 years notice, and I'll come back to"},{"startTime":556.316,"endTime":557.685,"body":"that at the end of the talk."},{"startTime":558.105,"endTime":562.155,"body":"Uh, you can live in peril and possible doom until then, I figure that will"},{"startTime":562.155,"endTime":565.125,"body":"make sure everyone listens, uh, to the rest of the talk."},{"startTime":565.705,"endTime":570.813,"body":"But I did say that these asteroids were useful, not just, uh, for not, or"},{"startTime":570.813,"endTime":571.154,"body":"interesting, not just because of their threat to us, but because they tell us about"},{"startTime":571.154,"endTime":577.285,"body":"our origins as well."},{"startTime":577.285,"endTime":579.685,"body":"They, they're the building blocks from which we build planets."},{"startTime":579.895,"endTime":584.765,"body":"We've actually got quite good as well of seeing that process unfold."},{"startTime":585.305,"endTime":588.65,"body":"Um, one place we could look to do that is actually really prominent in the"},{"startTime":588.65,"endTime":589.765,"body":"night sky at the minute."},{"startTime":589.875,"endTime":595.053,"body":"This is a beautiful picture by my friend Will Gator, uh, of the Orion constellation,"},{"startTime":595.053,"endTime":597.125,"body":"which perhaps some of you recognize."},{"startTime":597.125,"endTime":601.57,"body":"You've got the three stars in the belt, got Beetlejuice or Bettger at the top,"},{"startTime":601.57,"endTime":603.645,"body":"and then hanging down from the belt."},{"startTime":604.265,"endTime":606.605,"body":"Um, there is the sword of Orion."},{"startTime":607.785,"endTime":611.369,"body":"Um, and in that sword, if you go out tonight, I'm sure it's clear we're"},{"startTime":611.369,"endTime":612.325,"body":"giving a lecture inside."},{"startTime":612.385,"endTime":613.965,"body":"So it must be clear outside."},{"startTime":614.225,"endTime":617.255,"body":"If you go out and look up even from the middle of London, if you"},{"startTime":617.255,"endTime":620.285,"body":"look at the stars in the sword, you'll see that one of them is fuzzy."},{"startTime":620.995,"endTime":622.525,"body":"It's not an actual star."},{"startTime":622.945,"endTime":623.845,"body":"And this has been long known."},{"startTime":623.845,"endTime":625.085,"body":"It's this one, it's about halfway down."},{"startTime":625.085,"endTime":628.245,"body":"This is actually the great Orion Nebula."},{"startTime":628.595,"endTime":630.805,"body":"It's our nearest star forming nursery."},{"startTime":630.835,"endTime":637.13,"body":"This is a spectacular Hubble space telescope that shows nitrogen, hydrogen, oxygen, grass glowing in"},{"startTime":637.13,"endTime":637.55,"body":"this, uh, stellar nursery that's about 1500 light years away, relatively nearby in terms of"},{"startTime":637.55,"endTime":645.525,"body":"the structure of the galaxy."},{"startTime":646.515,"endTime":651.84,"body":"This nebula's lit up, not because the gas itself is intrinsically hot, but because it's"},{"startTime":651.84,"endTime":657.165,"body":"heated by a small cluster of stars that's visible at the center of the nebula."},{"startTime":657.345,"endTime":658.725,"body":"Um, they're called the trapezium."},{"startTime":658.725,"endTime":660.285,"body":"They're visible in a small telescope."},{"startTime":660.665,"endTime":665.458,"body":"Uh, and even through, uh, the six center reflector I have in my garden, I"},{"startTime":665.458,"endTime":665.778,"body":"spend ages looking at this, tele this object, because you could see this three dimensional"},{"startTime":665.778,"endTime":666.097,"body":"structure, this gas wrapped around these stars that have just formed in the heart of"},{"startTime":666.097,"endTime":675.685,"body":"this nebula."},{"startTime":675.955,"endTime":680.798,"body":"William Herschel, the great English observer who discovered with his sister the planet Uranus, um,"},{"startTime":680.798,"endTime":681.121,"body":"was the first one of the first to write about this as a star forming"},{"startTime":681.121,"endTime":685.965,"body":"region."},{"startTime":686.425,"endTime":692.336,"body":"And he described the nebula as being composed of the chaotic material of a thousand"},{"startTime":692.336,"endTime":693.125,"body":"future suns."},{"startTime":693.665,"endTime":698.245,"body":"And I think that captures something of the drama of these objects."},{"startTime":698.245,"endTime":703.25,"body":"You've got new stars forming their light, the winds from those stars sculpt the gas"},{"startTime":703.25,"endTime":703.584,"body":"around them, that can trigger further star formation and allow pe that allow stars to"},{"startTime":703.584,"endTime":709.925,"body":"form out of the gas."},{"startTime":710.505,"endTime":712.565,"body":"Um, and we learn a lot by studying these things."},{"startTime":713.225,"endTime":718.205,"body":"But we can also look very closely at the stars that are forming."},{"startTime":718.205,"endTime":721.605,"body":"This is something that the Hubble Space Telescope in particular specialized in."},{"startTime":722.025,"endTime":726.925,"body":"And these four dots, this is I'm afraid going to be a talk about blobs."},{"startTime":727.465,"endTime":728.845,"body":"So you've had the nice images."},{"startTime":728.985,"endTime":729.205,"body":"Now."},{"startTime":729.745,"endTime":731.805,"body":"So relax in, we're gonna talk about blobs."},{"startTime":732.145,"endTime":735.685,"body":"Uh, at the heart of each of these dots is a newly formed star."},{"startTime":736.055,"endTime":738.285,"body":"These are stars which have just switched on."},{"startTime":738.385,"endTime":741.405,"body":"So nuclear reactions at their center have just got going."},{"startTime":742.025,"endTime":748.617,"body":"Um, and what you can see in each of these cases, there's that silhouette against"},{"startTime":748.617,"endTime":749.057,"body":"the bright background of the gas in the nebula, there is a shadow, a silhouette,"},{"startTime":749.057,"endTime":759.605,"body":"uh, which is a disc of material around that star."},{"startTime":760.025,"endTime":761.485,"body":"Now, these are big discs."},{"startTime":761.665,"endTime":767.433,"body":"Um, on average, these four are about 60 billion miles across, which is about seven"},{"startTime":767.433,"endTime":770.125,"body":"and a half times our solar system."},{"startTime":770.185,"endTime":775.165,"body":"If you think of Neptune as the, the edge of the solar system, an idea"},{"startTime":775.165,"endTime":775.497,"body":"we'll come back to, um, so that they, they may be big compared to our"},{"startTime":775.497,"endTime":775.829,"body":"solar system, but we think these are in fact solar systems in the making as"},{"startTime":775.829,"endTime":776.161,"body":"well as gas In the nebula, we have dust, silicon, carbon, tiny grains, maybe 10th"},{"startTime":776.161,"endTime":791.765,"body":"the size of sand grains."},{"startTime":792.185,"endTime":796.919,"body":"Um, and as they get caught up in the formation of the star, they form"},{"startTime":796.919,"endTime":799.445,"body":"because of their angular momentum into these discs."},{"startTime":800.305,"endTime":803.005,"body":"Um, and the discs we now know have structure."},{"startTime":803.705,"endTime":808.748,"body":"So if we look not with the Hubble Space telescope, but with a telescope that's"},{"startTime":808.748,"endTime":809.085,"body":"tuned to the microwave region of the spectrum to very short wave radio, really, but"},{"startTime":809.085,"endTime":809.421,"body":"what astronomers call the sub-millimeter or microwave, then we can see some of these discs"},{"startTime":809.421,"endTime":819.845,"body":"in exquisite detail."},{"startTime":819.845,"endTime":823.445,"body":"We use that frequency 'cause it gets us to the cool parts of the solar"},{"startTime":823.445,"endTime":823.685,"body":"system."},{"startTime":823.985,"endTime":828.925,"body":"So here are three planet forming discs, stars at the center."},{"startTime":829.465,"endTime":833.207,"body":"Um, ignore the, well, there's a zoom in on the right there that in the"},{"startTime":833.207,"endTime":834.205,"body":"middle that shows detail."},{"startTime":834.505,"endTime":840.902,"body":"But what I want you to see is that these discs have structure, they have"},{"startTime":840.902,"endTime":841.328,"body":"gaps in them, they have rings, and that structure is caused by planets that are"},{"startTime":841.328,"endTime":849.005,"body":"forming within the disc."},{"startTime":849.865,"endTime":854.365,"body":"So once you form a planet, it can sweep up the dust in its orbit."},{"startTime":854.745,"endTime":857.965,"body":"And so we now think these, all these stars are a few million years old."},{"startTime":858.505,"endTime":863.239,"body":"And so we are looking at places where planets have formed within the last few"},{"startTime":863.239,"endTime":863.555,"body":"million years, probably big planets, Jupiter sized or more, but we're seeing their effects on"},{"startTime":863.555,"endTime":868.605,"body":"the disc."},{"startTime":869.025,"endTime":872.285,"body":"I'm a particular fan of the middle one, which is a star called tw hy."},{"startTime":872.825,"endTime":877.756,"body":"Um, because that first gap that you can see is one astronomical unit from the"},{"startTime":877.756,"endTime":878.085,"body":"star."},{"startTime":878.085,"endTime":882.39,"body":"In other words, it's the same distance from the star as the earth is from"},{"startTime":882.39,"endTime":882.965,"body":"the sun."},{"startTime":883.785,"endTime":889.205,"body":"So you can imagine looking at our inner soul system four and a half billion"},{"startTime":889.205,"endTime":889.567,"body":"years ago and seeing exactly this, we can also see that this is an evolutionary"},{"startTime":889.567,"endTime":899.325,"body":"process that this forming of planets and sweeping up a dust takes time."},{"startTime":899.415,"endTime":904.624,"body":"These are, uh, a recent view just from last year of 20 such discs all"},{"startTime":904.624,"endTime":908.445,"body":"from this telescope called Alma up in the high Chilean Andes."},{"startTime":908.985,"endTime":913.029,"body":"Uh, it's an amazing place and an amazing telescope, but they're a range from youngest"},{"startTime":913.029,"endTime":915.725,"body":"in the top left to oldest in the bottom right."},{"startTime":916.105,"endTime":922.488,"body":"And you can see what starts off as quite a amorphous, diffuse, diffuse structure becomes"},{"startTime":922.488,"endTime":923.765,"body":"a regular disc."},{"startTime":924.065,"endTime":928.285,"body":"And then those gaps appear by the time you get down to the bottom right."},{"startTime":929.065,"endTime":932.445,"body":"And so planets form after the discs."},{"startTime":932.445,"endTime":934.925,"body":"So you have the star collapse, you have the disc, and you have planets."},{"startTime":935.145,"endTime":939.507,"body":"And the fact that we can watch this happen is one of, I think, the"},{"startTime":939.507,"endTime":942.125,"body":"unsung triumphs of astronomy in the last 20 years."},{"startTime":942.125,"endTime":947.548,"body":"And I don't think anyone, even those building Elma, uh, 20 years ago realized we"},{"startTime":947.548,"endTime":951.525,"body":"were gonna get this sort of grandstand view on planet formation."},{"startTime":952.585,"endTime":955.725,"body":"Now, to explain what we're seeing, we have a couple of options."},{"startTime":956.145,"endTime":960.978,"body":"Um, one option, which is beloved by, by many of my colleagues, is of course"},{"startTime":960.978,"endTime":961.301,"body":"to build a, a high resolution computer simulation to take the physics that we understand"},{"startTime":961.301,"endTime":961.623,"body":"of these quite complicated systems, which involve fluid dynamics and the heating of the star"},{"startTime":961.623,"endTime":961.945,"body":"plus, uh, friction between grains in the disc, plus the gravitational interaction of the newly"},{"startTime":961.945,"endTime":976.125,"body":"forming planets."},{"startTime":976.265,"endTime":980.855,"body":"But we can throw all that in a very large computer and we could build"},{"startTime":980.855,"endTime":981.161,"body":"a convincing model with music apparently, um, that, I dunno if we have copyright clearance"},{"startTime":981.161,"endTime":986.365,"body":"for the music."},{"startTime":986.425,"endTime":987.445,"body":"So we'll stick to the image."},{"startTime":987.745,"endTime":990.365,"body":"Um, and what you could see in this beautiful, this is a simulation."},{"startTime":990.365,"endTime":994.37,"body":"It's not an an animation, but what you can see is that these gaps grow"},{"startTime":994.37,"endTime":994.637,"body":"naturally and then you start to gain some planets and it's rather beautiful and it's"},{"startTime":994.637,"endTime":999.445,"body":"all very, very convincing."},{"startTime":1000.865,"endTime":1003.165,"body":"The trouble is that the simulation's cheap."},{"startTime":1004.105,"endTime":1009.271,"body":"Um, there is a fundamental mystery at the heart of our understanding of planet formation,"},{"startTime":1009.271,"endTime":1013.405,"body":"and that's going to be a key part of this evening's lecture."},{"startTime":1013.785,"endTime":1014.925,"body":"So let's ignore the simulation."},{"startTime":1014.925,"endTime":1020.437,"body":"Just talk about first principles, what we're building these planets out of, of things like"},{"startTime":1020.437,"endTime":1020.805,"body":"this."},{"startTime":1021.635,"endTime":1024.723,"body":"This is a actual interstellar dust grain."},{"startTime":1025.145,"endTime":1028.805,"body":"It was captured by a spacecraft called Stardust."},{"startTime":1029.135,"endTime":1031.685,"body":"There was sort of a, a precursor to azaria's."},{"startTime":1031.723,"endTime":1034.165,"body":"Rex actually visited, not an asteroid, but a comet."},{"startTime":1034.545,"endTime":1039.904,"body":"It flew through, uh, the coma, the atmosphere of Comet Vilt two and returned to"},{"startTime":1039.904,"endTime":1042.405,"body":"earth with lots of nice commentary particles."},{"startTime":1043.665,"endTime":1049.965,"body":"But by accident, without planning, some particles got stuck on the back of the detector."},{"startTime":1050.385,"endTime":1054.822,"body":"Now a few of those were comet bits that had bounced off the spacecraft and"},{"startTime":1054.822,"endTime":1058.965,"body":"ended up there, but it was also the back was exposed to interstellar space."},{"startTime":1059.745,"endTime":1065.31,"body":"And so six particles, I think that were passing through the solar system, happened to"},{"startTime":1065.31,"endTime":1067.165,"body":"be captured by the detector."},{"startTime":1067.265,"endTime":1071.274,"body":"And they were found by a bunch of citizen scientists online in a product called"},{"startTime":1071.274,"endTime":1071.541,"body":"Stardust at home that spent their life looking at dust grains and looking for ones"},{"startTime":1071.541,"endTime":1076.085,"body":"that looked unusual."},{"startTime":1076.585,"endTime":1079.605,"body":"Uh, the unusual ones were extracted, tested in the lab."},{"startTime":1079.905,"endTime":1082.485,"body":"And so this is a piece of another solar system."},{"startTime":1082.985,"endTime":1084.725,"body":"Um, as you can see, it's pretty small."},{"startTime":1084.725,"endTime":1087.925,"body":"There's a scale bar at the top and it's this irregular structure."},{"startTime":1088.705,"endTime":1093.3,"body":"And the reason it looks like this is that it started life as a bunch"},{"startTime":1093.3,"endTime":1095.445,"body":"of little spherical grains, again, thinks grains."},{"startTime":1095.865,"endTime":1100.45,"body":"And when they collide in a disc like those we see around these young stars,"},{"startTime":1100.45,"endTime":1100.756,"body":"they stick together and they stick together because of chemical reactions, but also 'cause they"},{"startTime":1100.756,"endTime":1101.062,"body":"often in the outer bits of the solar system have ice, water, ice or carbon"},{"startTime":1101.062,"endTime":1110.845,"body":"monoxide ice surrounding them."},{"startTime":1110.845,"endTime":1114.365,"body":"And you get two nice icy grains, you stick them together."},{"startTime":1114.545,"endTime":1119.08,"body":"My friend Helen Fraser does this, uh, on a zero gravity on a plane that"},{"startTime":1119.08,"endTime":1119.685,"body":"does this."},{"startTime":1119.745,"endTime":1122.645,"body":"So she gets a few minutes each time to try and stick dust grains together."},{"startTime":1123.345,"endTime":1128.102,"body":"Um, I think I've probably underestimated the, or not explained the complexity of her experiment,"},{"startTime":1128.102,"endTime":1130.005,"body":"but that's fundamentally what she's doing."},{"startTime":1130.545,"endTime":1131.765,"body":"Um, and this works."},{"startTime":1131.825,"endTime":1136.433,"body":"And so over time what's happening in those discs is you're slowly sticking together bigger"},{"startTime":1136.433,"endTime":1136.74,"body":"and bigger things to, you go from dust grains to aggregates like this one to"},{"startTime":1136.74,"endTime":1142.885,"body":"maybe as much as a pebble."},{"startTime":1143.465,"endTime":1147.894,"body":"And then if you start sticking pebbles together, they're moving together, that can happen between"},{"startTime":1147.894,"endTime":1148.485,"body":"the friction."},{"startTime":1148.675,"endTime":1151.405,"body":"Then you end up with things maybe the size of a boulder."},{"startTime":1152.265,"endTime":1155.787,"body":"So I have a, I have my own simulation, uh, of this process for you,"},{"startTime":1155.787,"endTime":1158.605,"body":"which I, I think is as high tech as the previous ones."},{"startTime":1158.605,"endTime":1159.565,"body":"So this is a bowl of water."},{"startTime":1160.345,"endTime":1162.885,"body":"Uh, it's being stirred to simulate the disc."},{"startTime":1163.025,"endTime":1164.525,"body":"So this is the rotating disc."},{"startTime":1165.065,"endTime":1169.459,"body":"And then we're going to introduce some grains in this case of pepper, uh, into"},{"startTime":1169.459,"endTime":1170.045,"body":"the bowl."},{"startTime":1170.625,"endTime":1172.445,"body":"And this will be utterly unspectacular."},{"startTime":1172.725,"endTime":1177.466,"body":"'cause initially you won't see the pepper, but as it rotates, friction brings them together,"},{"startTime":1177.466,"endTime":1177.783,"body":"the pepper grains starts sticking together and they become visible in the video because they've"},{"startTime":1177.783,"endTime":1182.525,"body":"grown."},{"startTime":1182.825,"endTime":1184.365,"body":"So this is exactly the same process."},{"startTime":1185.185,"endTime":1188.525,"body":"Um, I'm not saying planets are made of pepper, but you, you get the idea."},{"startTime":1189.105,"endTime":1191.165,"body":"So this works fine until you get to boulders."},{"startTime":1192.145,"endTime":1197.632,"body":"And the trouble is, once you go from here to a boulder, when I collide"},{"startTime":1197.632,"endTime":1200.925,"body":"to boulders together, I don't get a bigger boulder."},{"startTime":1202.045,"endTime":1205.685,"body":"I get rubble, I go backwards, I get smaller things."},{"startTime":1206.465,"endTime":1207.445,"body":"And so this is a problem."},{"startTime":1207.595,"endTime":1210.805,"body":"I've broken the chain of getting larger and larger and growing towards the planet."},{"startTime":1210.945,"endTime":1215.558,"body":"Now, once I get to things roughly the size of, I don't know, one of"},{"startTime":1215.558,"endTime":1215.865,"body":"the buildings around us here in the city, when I climb two skyscraper size things"},{"startTime":1215.865,"endTime":1223.555,"body":"together, I get rubble, but I get a lot of it."},{"startTime":1223.575,"endTime":1226.475,"body":"And gravity can pull that back together."},{"startTime":1227.215,"endTime":1230.795,"body":"So once you get to big things and they collide, gravity is important."},{"startTime":1231.135,"endTime":1233.995,"body":"And so we can grow from skyscrapers to planets."},{"startTime":1234.055,"endTime":1235.115,"body":"We understand how that happens."},{"startTime":1235.535,"endTime":1240.069,"body":"And we can go from dust grains to boulders, but we don't know how to"},{"startTime":1240.069,"endTime":1240.371,"body":"quickly jump that gap in the middle as long as you let me click my"},{"startTime":1240.371,"endTime":1246.115,"body":"fingers and cross that gap."},{"startTime":1246.195,"endTime":1247.485,"body":"I know how to form planets."},{"startTime":1248.345,"endTime":1251.205,"body":"But there's this fundamental problem in the middle."},{"startTime":1251.745,"endTime":1257.754,"body":"And that's the problem that I think a solution may have appeared in our solar"},{"startTime":1257.754,"endTime":1258.155,"body":"system."},{"startTime":1258.495,"endTime":1259.435,"body":"We weren't looking for it."},{"startTime":1259.435,"endTime":1264.403,"body":"This wasn't the result of a targeted search for a solution to this problem, nor"},{"startTime":1264.403,"endTime":1264.735,"body":"was it particularly, uh, a targeted search for objects like the one I'm going to"},{"startTime":1264.735,"endTime":1270.035,"body":"talk about."},{"startTime":1270.575,"endTime":1275.555,"body":"Um, the discovery was made by telescopes in these two small domes, which are in"},{"startTime":1275.555,"endTime":1278.875,"body":"an observatory on top of the Hawaiian island of Maui."},{"startTime":1279.375,"endTime":1285.63,"body":"Um, it's a experiment called pan stars, which is funded by consortium of academic institutions"},{"startTime":1285.63,"endTime":1290.635,"body":"and the US Air Force to look for threatening near earth asteroids."},{"startTime":1291.255,"endTime":1295.625,"body":"So the fact that we know that there's nothing more threatening than Benu that's large"},{"startTime":1295.625,"endTime":1299.995,"body":"and heading our way is primarily due to pan stars and, and surveys like it."},{"startTime":1299.995,"endTime":1304.755,"body":"What they do is they scan the whole sky and they look for moving objects."},{"startTime":1305.615,"endTime":1309.795,"body":"And in October, 2017, they found such an object."},{"startTime":1309.795,"endTime":1314.475,"body":"This is, these are images from the 19th of October on the left."},{"startTime":1315.095,"endTime":1319.155,"body":"The red lines, by the way, are areas where there's no data available."},{"startTime":1319.855,"endTime":1324.409,"body":"The US Air Force having funded this mission, realize that it, if you're looking for"},{"startTime":1324.409,"endTime":1324.713,"body":"moving objects in the sky, you also find things the US Air Force doesn't want"},{"startTime":1324.713,"endTime":1329.875,"body":"you to find."},{"startTime":1330.495,"endTime":1334.606,"body":"And so they remove bits of the sky from our data, uh, to hide what"},{"startTime":1334.606,"endTime":1335.155,"body":"they're doing."},{"startTime":1335.155,"endTime":1338.115,"body":"Then they have to remove bits of the sky that don't hide what they're doing."},{"startTime":1338.395,"endTime":1340.675,"body":"'cause otherwise, so, so the red lines are just that."},{"startTime":1341.135,"endTime":1343.635,"body":"But I dunno if you can see in the red circle, which I added."},{"startTime":1344.055,"endTime":1347.224,"body":"Uh, it would be really nice if the Air Force would circle the things we're"},{"startTime":1347.224,"endTime":1348.915,"body":"looking for, but we haven't got there yet."},{"startTime":1349.095,"endTime":1351.555,"body":"Um, there's a very faint smudge."},{"startTime":1352.105,"endTime":1353.115,"body":"It's a little line."},{"startTime":1354.135,"endTime":1356.195,"body":"Um, and that's a moving object."},{"startTime":1357.215,"endTime":1358.155,"body":"It seemed unusual."},{"startTime":1358.375,"endTime":1363.631,"body":"It was followed up by a larger telescope on the neighboring big islander Hawaii on"},{"startTime":1363.631,"endTime":1366.435,"body":"monarchy by CFHT, the Canada France, Hawaii telescope."},{"startTime":1366.615,"endTime":1370.984,"body":"And that image is much clearer on the right now, this time they're moving the"},{"startTime":1370.984,"endTime":1373.315,"body":"telescope to follow whatever this new object is."},{"startTime":1373.335,"endTime":1374.915,"body":"So the.is the new object."},{"startTime":1375.575,"endTime":1378.875,"body":"The lines here are stars that move relative to the thing."},{"startTime":1378.935,"endTime":1381.275,"body":"So we know it's moving relative to the stars."},{"startTime":1382.095,"endTime":1384.875,"body":"Um, in the bottom there's also a closeup image."},{"startTime":1385.375,"endTime":1388.675,"body":"Um, and all it really tells you is that this is a point like source."},{"startTime":1388.745,"endTime":1389.755,"body":"It's not a big thing."},{"startTime":1389.985,"endTime":1391.875,"body":"It's not a comet at this stage with a tail."},{"startTime":1391.875,"endTime":1393.915,"body":"It's just a.in the sky."},{"startTime":1394.735,"endTime":1399.298,"body":"And at this point, most people are thinking this is in fact an interloper from"},{"startTime":1399.298,"endTime":1400.515,"body":"the outer solar system."},{"startTime":1401.215,"endTime":1406.237,"body":"So our familiar model of the solar system with the planets, with Mercury, Venus, earth,"},{"startTime":1406.237,"endTime":1406.572,"body":"Mars, Jupiter, Saturn, Eunice, Neptune, um, that's just the, the inner bit of our solar"},{"startTime":1406.572,"endTime":1411.595,"body":"system."},{"startTime":1411.625,"endTime":1416.097,"body":"Most objects in the solar system, uh, live out in what's called the AUT cloud,"},{"startTime":1416.097,"endTime":1419.675,"body":"which is about a third of the way to the nearest star."},{"startTime":1420.255,"endTime":1425.113,"body":"And this is the vast reservoir of icy bodies left over from when the solar"},{"startTime":1425.113,"endTime":1426.085,"body":"system was forming."},{"startTime":1426.625,"endTime":1431.382,"body":"Um, that feeds into our store of comics that we see icy bodies that come"},{"startTime":1431.382,"endTime":1433.285,"body":"into the inter inner solar system."},{"startTime":1433.625,"endTime":1438.92,"body":"So people are thinking this as a comet and they began to plot its trajectory"},{"startTime":1438.92,"endTime":1440.685,"body":"and it was immediately unusual."},{"startTime":1440.985,"endTime":1442.165,"body":"So there's the solar system."},{"startTime":1442.705,"endTime":1447.405,"body":"Um, the dotted line shows the path on which this object traveled."},{"startTime":1447.545,"endTime":1452.368,"body":"It came down from up in the north, came rapidly into the solar system, slingshot"},{"startTime":1452.368,"endTime":1452.69,"body":"it around the sun, and by the time it was discovered, was already heading off"},{"startTime":1452.69,"endTime":1459.765,"body":"into the distant galaxy back into deep space."},{"startTime":1459.945,"endTime":1463.045,"body":"And we found it after it had been through the inner solar system."},{"startTime":1463.315,"endTime":1464.845,"body":"There's an animated version here."},{"startTime":1464.845,"endTime":1466.245,"body":"It's got a few other objects in."},{"startTime":1466.545,"endTime":1471.905,"body":"Uh, but it's this red line coming in here, uh, and there's this slingshot and"},{"startTime":1471.905,"endTime":1474.765,"body":"then it heads off out into deep space."},{"startTime":1475.505,"endTime":1480.783,"body":"And this trajectory was unusual enough that we realized, it was realized that this was"},{"startTime":1480.783,"endTime":1481.135,"body":"the first interstellar object, the first large object bigger than a dust brain that we'd"},{"startTime":1481.135,"endTime":1490.285,"body":"seen coming from another solar system, or at least from beyond ours."},{"startTime":1490.785,"endTime":1494.355,"body":"And so the question at the beginning about the name, well, it was originally classified"},{"startTime":1494.355,"endTime":1497.925,"body":"as an asteroid, then it was named then it was decided it was a comet."},{"startTime":1498.145,"endTime":1500.045,"body":"And eventually they gave it the designation."},{"startTime":1500.045,"endTime":1505.539,"body":"The International Astronomical Union gave it the designation one, i the first interstellar object and"},{"startTime":1505.539,"endTime":1507.005,"body":"the name Ua Mu."},{"startTime":1507.225,"endTime":1511.285,"body":"Now it's a Hawaiian name because it was discovered in a Hawaiian observatory."},{"startTime":1511.665,"endTime":1512.645,"body":"Uh, in Hawaiian."},{"startTime":1513.025,"endTime":1515.165,"body":"Um, emphasis comes from repetition."},{"startTime":1515.825,"endTime":1517.925,"body":"So MUA means far away."},{"startTime":1518.345,"endTime":1520.605,"body":"So UA is really far away."},{"startTime":1521.025,"endTime":1523.765,"body":"And UA is U is a scout."},{"startTime":1524.545,"endTime":1529.245,"body":"Um, so it's the scout from really, really far away, which is rather nice."},{"startTime":1529.665,"endTime":1532.485,"body":"And I'm now gonna show you, and I want you to be impressed, please."},{"startTime":1532.485,"endTime":1535.335,"body":"This is lecture three, so I know at least some of you are up for"},{"startTime":1535.335,"endTime":1535.525,"body":"this."},{"startTime":1535.945,"endTime":1540.35,"body":"Um, this is the best image that we have of this object that I'm basing"},{"startTime":1540.35,"endTime":1541.525,"body":"an entire lecture on."},{"startTime":1541.815,"endTime":1542.165,"body":"Ready?"},{"startTime":1542.915,"endTime":1543.205,"body":"Okay."},{"startTime":1543.705,"endTime":1547.685,"body":"Try to contain yourselves, \u003claugh\u003e, it's the thing in the blue circle."},{"startTime":1547.905,"endTime":1549.045,"body":"And I added the circle."},{"startTime":1550.265,"endTime":1553.725,"body":"Um, we never saw it as more than a dot, sadly."},{"startTime":1554.505,"endTime":1558.919,"body":"Um, this is an image from the very large telescope, one of the most powerful"},{"startTime":1558.919,"endTime":1560.685,"body":"instruments we have, hence the name."},{"startTime":1561.145,"endTime":1566.182,"body":"Um, again, tracking the object so that the stars blur in the background, but we"},{"startTime":1566.182,"endTime":1569.205,"body":"never rea saw it as more than a dot."},{"startTime":1569.345,"endTime":1570.925,"body":"And so it became a bit of a challenge."},{"startTime":1571.235,"endTime":1577.445,"body":"What can astronomers learn about an object if all we see is a dot?"},{"startTime":1578.115,"endTime":1580.822,"body":"Well, the first thing we can do is we can say, I, this is the"},{"startTime":1580.822,"endTime":1581.725,"body":"kind of astronomy I like."},{"startTime":1581.745,"endTime":1583.165,"body":"We ask simple questions."},{"startTime":1583.985,"endTime":1586.645,"body":"We know it came from beyond the solar system 'cause we've seen how it's moving."},{"startTime":1586.985,"endTime":1588.965,"body":"Um, we can say, what color is it?"},{"startTime":1589.305,"endTime":1591.165,"body":"It turns out it's slightly reddish."},{"startTime":1591.825,"endTime":1595.125,"body":"Uh, and that's typical of stuff in the outer solar system."},{"startTime":1595.265,"endTime":1599.532,"body":"So you could compare this with, I know Charan, one of the moons of Pluto,"},{"startTime":1599.532,"endTime":1599.817,"body":"or, uh, perhaps some of the objects in the CO about the rubble that shares"},{"startTime":1599.817,"endTime":1606.645,"body":"an orbit with Pluto, it wouldn't look out of place."},{"startTime":1606.745,"endTime":1611.136,"body":"And so that means it's probably icy and it's probably spent a lot of time"},{"startTime":1611.136,"endTime":1611.429,"body":"in deep space, or at least formed whichever solar system it came from on the"},{"startTime":1611.429,"endTime":1617.285,"body":"outer edges of its solar system."},{"startTime":1617.745,"endTime":1618.685,"body":"You could swap it there."},{"startTime":1618.685,"endTime":1619.725,"body":"So that, that makes sense."},{"startTime":1620.945,"endTime":1624.975,"body":"The other thing that we can do, if we measured color and we've seen it's"},{"startTime":1624.975,"endTime":1627.125,"body":"a dot, we can keep looking at it."},{"startTime":1627.305,"endTime":1632.573,"body":"And it was followed for a few months and it actually showed remarkable variation in"},{"startTime":1632.573,"endTime":1632.925,"body":"brightness."},{"startTime":1633.585,"endTime":1636.165,"body":"So this is, each.here is a measure of brightness."},{"startTime":1636.165,"endTime":1637.525,"body":"When it's high up, it's bright."},{"startTime":1637.525,"endTime":1641.061,"body":"When it's low down, its fa And this is from a whole cluster of the"},{"startTime":1641.061,"endTime":1642.005,"body":"world's most powerful telescopes."},{"startTime":1642.265,"endTime":1645.502,"body":"But you can see there's this pattern where it goes up and down in brightness"},{"startTime":1645.502,"endTime":1647.445,"body":"and then it goes up quickly and then down."},{"startTime":1647.785,"endTime":1649.325,"body":"But it's not a regular pattern."},{"startTime":1649.555,"endTime":1653.935,"body":"It's not, um, a simple periodic relationship."},{"startTime":1654.435,"endTime":1658.305,"body":"And so the change in brightness is quite big."},{"startTime":1658.965,"endTime":1663.681,"body":"Um, it's about a factor of 10, uh, between its brightest and its faint as"},{"startTime":1663.681,"endTime":1664.625,"body":"it caused havoc."},{"startTime":1664.625,"endTime":1666.425,"body":"We're trying to plan to observe it."},{"startTime":1666.685,"endTime":1669.665,"body":"So we've got this unknown object that's changing brightness wildly."},{"startTime":1669.665,"endTime":1673.865,"body":"And so the astronomers who did this, uh, had to be really on it."},{"startTime":1674.365,"endTime":1679.585,"body":"And very quickly there were two hypotheses about what's causing this change in brightness."},{"startTime":1680.205,"endTime":1681.225,"body":"And they're illustrated."},{"startTime":1681.685,"endTime":1685.105,"body":"And normally for these lectures, I, I've been trying to make my own slides 'cause"},{"startTime":1685.105,"endTime":1685.333,"body":"I want to give you the most original and, and interesting content, but I had"},{"startTime":1685.333,"endTime":1689.665,"body":"to borrow this next one."},{"startTime":1689.665,"endTime":1694.722,"body":"This is an illustration by my friend Luke Duns about the two reasons why URA"},{"startTime":1694.722,"endTime":1696.745,"body":"might have been changing in brightness."},{"startTime":1696.745,"endTime":1700.905,"body":"And he's using a local object to stand in for amu mua \u003claugh\u003e."},{"startTime":1702.245,"endTime":1705.025,"body":"So the two options are on the right."},{"startTime":1705.165,"endTime":1708.585,"body":"You have, uh, str structure on the surface."},{"startTime":1709.405,"endTime":1712.505,"body":"We could have colored patches, we could have dark patches and light patches."},{"startTime":1712.525,"endTime":1717.907,"body":"And so if you imagine the cat rotating, the brightness of the cat would change"},{"startTime":1717.907,"endTime":1718.625,"body":"over time."},{"startTime":1719.085,"endTime":1723.001,"body":"Um, I'm told by Luke, he tried to make the cat do this, but apparently"},{"startTime":1723.001,"endTime":1723.785,"body":"difficult to coordinate."},{"startTime":1724.205,"endTime":1725.945,"body":"Um, so that's possible."},{"startTime":1726.645,"endTime":1729.825,"body":"You can imagine inventing a, a pattern that would match what we've seen."},{"startTime":1729.825,"endTime":1734.946,"body":"But if you look in our solar system with one honorable exception, Saturn's moon iapetus,"},{"startTime":1734.946,"endTime":1739.385,"body":"which is half dark and half white, we don't see on small bodies."},{"startTime":1740.685,"endTime":1745.889,"body":"And we know that m is small because it's a dot, um, on small bodies,"},{"startTime":1745.889,"endTime":1748.665,"body":"we don't see variations in, in color really."},{"startTime":1748.665,"endTime":1750.225,"body":"They tend to be pretty monochrome."},{"startTime":1750.365,"endTime":1752.105,"body":"So this is possible but unlikely."},{"startTime":1752.805,"endTime":1755.305,"body":"Uh, in the other example, we have a stretched object."},{"startTime":1756.005,"endTime":1760.96,"body":"And if you have a stretched object, and this was the, uh, press release image"},{"startTime":1760.96,"endTime":1761.291,"body":"that you'll have seen perhaps as the most common, um, visualization of a, remember if"},{"startTime":1761.291,"endTime":1761.621,"body":"you have a long object, then it's brightness depends very much on whether you are"},{"startTime":1761.621,"endTime":1773.185,"body":"looking, uh, edge on or side on."},{"startTime":1773.245,"endTime":1776.825,"body":"So this will look very different from this, if that makes any sense."},{"startTime":1776.845,"endTime":1780.505,"body":"And if it's, if it's rotating, then you get a change over time."},{"startTime":1781.545,"endTime":1784.685,"body":"And in fact, it's not just rotating, it's tumbling."},{"startTime":1785.385,"endTime":1788.605,"body":"So it's not just go, it's going end over end, but twisting as it does."},{"startTime":1788.625,"endTime":1788.845,"body":"So."},{"startTime":1789.545,"endTime":1793.365,"body":"And if you model that, you can reproduce the light curve pretty well."},{"startTime":1793.385,"endTime":1798.529,"body":"Now, the original estimates were that this thing must be 400 meters long, 10 times"},{"startTime":1798.529,"endTime":1802.645,"body":"or maybe even as 20 times as long as it is white."},{"startTime":1803.025,"endTime":1806.325,"body":"So it's this really extreme sort of cigar shaped thing."},{"startTime":1806.855,"endTime":1810.845,"body":"Later estimates, I think most people now would be a bit more restrained."},{"startTime":1810.845,"endTime":1816.371,"body":"They would now say it's more pancake than, um, cigar, maybe six times as long"},{"startTime":1816.371,"endTime":1817.845,"body":"as it is white."},{"startTime":1818.265,"endTime":1822.685,"body":"But you've still got this elongated structure tumbling through the solar system."},{"startTime":1822.785,"endTime":1823.605,"body":"Why is it tumbling?"},{"startTime":1824.265,"endTime":1824.685,"body":"Not sure."},{"startTime":1824.685,"endTime":1830.122,"body":"Maybe a violent start wherever it came from, something flicked it into, uh, into galactic"},{"startTime":1830.122,"endTime":1830.485,"body":"space."},{"startTime":1830.485,"endTime":1831.085,"body":"We're not sure."},{"startTime":1831.425,"endTime":1833.725,"body":"Uh, but that explains the change of brightness."},{"startTime":1834.305,"endTime":1838.085,"body":"And before you stare too long at this artist's impression, I want to remind you"},{"startTime":1838.085,"endTime":1840.605,"body":"that this is the best image that we've got, right?"},{"startTime":1840.885,"endTime":1845.303,"body":"\u003claugh\u003e, uh, not this or this, this, we're talking about the real stuff, but we"},{"startTime":1845.303,"endTime":1847.365,"body":"think it might have looked like this."},{"startTime":1848.225,"endTime":1852.485,"body":"So, you know, we, we can imagine, but we must always remain grounded in reality."},{"startTime":1854.015,"endTime":1857.485,"body":"There were two other odd things about this object."},{"startTime":1857.505,"endTime":1859.645,"body":"So the color unusual but not that unusual."},{"startTime":1859.705,"endTime":1864.005,"body":"The shape pretty unusual compared to the asteroids that we've studied in the solar system."},{"startTime":1864.335,"endTime":1865.645,"body":"There were two other unusual things."},{"startTime":1865.825,"endTime":1871.184,"body":"One is that that trajectory where it came in originally seemed to be close to"},{"startTime":1871.184,"endTime":1873.685,"body":"something called the local standard of rest."},{"startTime":1874.075,"endTime":1878.39,"body":"What that means is it seemed before it encountered the solar system to be moving"},{"startTime":1878.39,"endTime":1880.405,"body":"along with the nearest stars to us."},{"startTime":1881.345,"endTime":1882.885,"body":"So is that unusual?"},{"startTime":1882.935,"endTime":1883.365,"body":"Don't know."},{"startTime":1883.365,"endTime":1887.468,"body":"We've only seen one of these things, but if you were going to throw these"},{"startTime":1887.468,"endTime":1887.741,"body":"things randomly around the galaxy, you wouldn't expect it, uh, to be following the nearby"},{"startTime":1887.741,"endTime":1891.845,"body":"stars."},{"startTime":1891.845,"endTime":1893.965,"body":"So maybe it comes from one of those nearby stars."},{"startTime":1894.265,"endTime":1899.468,"body":"And then the real mystery is that as we watched it recede from the solar"},{"startTime":1899.468,"endTime":1904.325,"body":"system, we're expecting it to slow down because of the gravity of the sun."},{"startTime":1904.675,"endTime":1907.005,"body":"Leaving the solar system takes energy."},{"startTime":1907.025,"endTime":1908.965,"body":"You have to climb out of the sun's gravity."},{"startTime":1909.075,"endTime":1916.245,"body":"Well, and escape umo did slow down a bit, but much less than we thought."},{"startTime":1916.535,"endTime":1921.405,"body":"There was some accelerating force pushing it out of the solar system."},{"startTime":1923.035,"endTime":1925.525,"body":"This would make sense if it was a comet."},{"startTime":1925.525,"endTime":1926.565,"body":"We've seen comets."},{"startTime":1926.565,"endTime":1931.459,"body":"This is the closeup nucleus of Cher Mary of Garca, which was visited by, I"},{"startTime":1931.459,"endTime":1932.765,"body":"mostly put it in."},{"startTime":1932.765,"endTime":1936.765,"body":"So I could say Cher Garca, because once you've learn to do that, you use"},{"startTime":1936.765,"endTime":1938.365,"body":"that skill as often as possible."},{"startTime":1938.685,"endTime":1943.185,"body":"\u003claugh\u003e, it's like trying to pronounce the Icelandic volcano that caused, uh, the dust storm"},{"startTime":1943.185,"endTime":1944.685,"body":"more than a decade ago."},{"startTime":1944.925,"endTime":1950.002,"body":"Esther Fuk, if you were, uh, asking, anyway, char Garca, the other chairman Goenka story"},{"startTime":1950.002,"endTime":1950.341,"body":"is that it was, uh, nicknamed chewy, gooey by the scientists who built the probe"},{"startTime":1950.341,"endTime":1950.679,"body":"that went there until they worked out that both Cher and Goenka were still around"},{"startTime":1950.679,"endTime":1963.205,"body":"and we'd prefer not to have their discovery shortened."},{"startTime":1963.305,"endTime":1968.205,"body":"So, and we can call it 67 p uh, this is the come we know"},{"startTime":1968.205,"endTime":1972.125,"body":"best Rosetta spent, uh, more than a year in orbit around it."},{"startTime":1972.225,"endTime":1977.375,"body":"And as you can see, this is in active phase and there's this jet of"},{"startTime":1977.375,"endTime":1978.405,"body":"materials shooting out."},{"startTime":1978.465,"endTime":1983.415,"body":"So comets, which are made of ice don't melt evenly when they come into the"},{"startTime":1983.415,"endTime":1984.405,"body":"inner solar system."},{"startTime":1985.385,"endTime":1987.605,"body":"You get these dramatic jets."},{"startTime":1987.605,"endTime":1991.885,"body":"And so that will have a rocket effect pushing this thing and this image up."},{"startTime":1992.345,"endTime":1997.513,"body":"And so if Uma was only a comet, then this acceleration would make no sense,"},{"startTime":1997.513,"endTime":1999.925,"body":"but it's only a point of light."},{"startTime":2000.705,"endTime":2003.205,"body":"How do we explain this acceleration?"},{"startTime":2004.305,"endTime":2008.245,"body":"So we have a, a first visitor to the solar system."},{"startTime":2009.705,"endTime":2012.285,"body":"We dunno where it came from, but we know it came from somewhere else."},{"startTime":2013.145,"endTime":2018.805,"body":"It appeared unannounced, it moved through the solar system silently."},{"startTime":2019.345,"endTime":2022.929,"body":"And we know we checked, we pointed radio telescopes at it just in case there"},{"startTime":2022.929,"endTime":2023.885,"body":"were signals being sent."},{"startTime":2024.385,"endTime":2028.458,"body":"Uh, there weren't, or at least none that we could hear, but now it's speeding"},{"startTime":2028.458,"endTime":2031.445,"body":"up as it leaves almost as if it's fired it's engines."},{"startTime":2032.505,"endTime":2038.498,"body":"And all of these thoughts combined with the fact that Arthur C. Clark wrote a"},{"startTime":2038.498,"endTime":2038.898,"body":"book called Rendezvous with Rama, uh, back, uh, 50 years or so ago, which subscribes"},{"startTime":2038.898,"endTime":2039.298,"body":"the visit to the solar system of a mysterious long cylindrical object which passes silently"},{"startTime":2039.298,"endTime":2052.085,"body":"through the solar system."},{"startTime":2052.264,"endTime":2058.114,"body":"And despite in the book, um, people going to visit it and exploring it inside,"},{"startTime":2058.114,"endTime":2059.284,"body":"it's obviously artificial."},{"startTime":2059.585,"endTime":2065.12,"body":"Uh, it remains mysterious and disappears off into the, uh, rest of the galaxy firing"},{"startTime":2065.12,"endTime":2066.965,"body":"its engines as it goes."},{"startTime":2067.145,"endTime":2072.535,"body":"So, you know, this idea that maybe this is exactly the behavior that one would"},{"startTime":2072.535,"endTime":2072.895,"body":"expect, uh, from an alien spacecraft was something that occurred to to lots of us"},{"startTime":2072.895,"endTime":2079.005,"body":"at the time."},{"startTime":2079.105,"endTime":2083.843,"body":"It also occurred to a Harvard astronomer called Avi Loeb, uh, who believes, uh, very"},{"startTime":2083.843,"endTime":2084.159,"body":"seriously that this is clearly an alien spacecraft and has written a 250 page book"},{"startTime":2084.159,"endTime":2093.005,"body":"explaining why the rest of us are too stupid to agree with him \u003claugh\u003e."},{"startTime":2093.005,"endTime":2096.725,"body":"Um, but it's a serious scientific point."},{"startTime":2096.824,"endTime":2103.901,"body":"We have an unusual set of properties should we consider, uh, an alien spacecraft as"},{"startTime":2103.901,"endTime":2104.845,"body":"a possibility."},{"startTime":2107.115,"endTime":2110.94,"body":"It's so tempted to say yes and leave \u003claugh\u003e, but actually I think there are"},{"startTime":2110.94,"endTime":2111.195,"body":"good explanations for the unusual things that we know about, um, mu So I'm gonna"},{"startTime":2111.195,"endTime":2111.45,"body":"tell you about them and then I'm going to try and convince you that it's"},{"startTime":2111.45,"endTime":2118.845,"body":"interesting."},{"startTime":2118.905,"endTime":2125.125,"body":"Anyway, the trouble with mentioning aliens is that people always want it to be aliens."},{"startTime":2125.285,"endTime":2129.351,"body":"I try to write a book, um, called It's Never Aliens, which was gonna be"},{"startTime":2129.351,"endTime":2132.605,"body":"a story about all the things that turn out not to be."},{"startTime":2132.605,"endTime":2136.805,"body":"And I got a a one line review from a potential publisher that just said,"},{"startTime":2136.805,"endTime":2141.005,"body":"but we wish it was, which is fair, but this is still an exciting object."},{"startTime":2141.005,"endTime":2142.365,"body":"But let's deal with the unusual things."},{"startTime":2142.635,"endTime":2145.725,"body":"Firstly, the shape this, this elongated shape and its color."},{"startTime":2145.795,"endTime":2150.07,"body":"Well, if you talk to people who study the small bodies of the solar system,"},{"startTime":2150.07,"endTime":2150.355,"body":"people like my friend Michelle Banister, they'll tell you that the most unusual thing about"},{"startTime":2150.355,"endTime":2157.765,"body":"this object is that we've studied it in this detail at all."},{"startTime":2157.905,"endTime":2162.166,"body":"If you ask the people who control the very large telescope to look at a"},{"startTime":2162.166,"endTime":2162.45,"body":"random asteroid that's only 200 meters across of which there are millions and perhaps billions"},{"startTime":2162.45,"endTime":2170.405,"body":"in the solar system, they're gonna tell you they've got better things to do."},{"startTime":2170.405,"endTime":2175.532,"body":"Looking at Jupiter and distant galaxies and planets around other stars and all the other"},{"startTime":2175.532,"endTime":2177.925,"body":"things that we are doing as astrophysicists."},{"startTime":2178.745,"endTime":2183.413,"body":"So if you took it and put it amongst its peers in the soul system,"},{"startTime":2183.413,"endTime":2186.525,"body":"it may not appear that unusual in shape or color."},{"startTime":2187.785,"endTime":2191.443,"body":"The fact that it's close to the local standard of rest, that it's moving with"},{"startTime":2191.443,"endTime":2191.687,"body":"the stars, it turns out it's not that close and that you could have got,"},{"startTime":2191.687,"endTime":2196.565,"body":"uh, that alignment by, by luck."},{"startTime":2197.025,"endTime":2200.951,"body":"Um, and then there's this acceleration, this fact that it fired its engines or, or"},{"startTime":2200.951,"endTime":2203.045,"body":"sped up as it left the solar system."},{"startTime":2203.355,"endTime":2205.845,"body":"Well we think we've got a couple of explanations for that as well."},{"startTime":2206.625,"endTime":2212.765,"body":"One is that, um, things are changed by time in space."},{"startTime":2213.475,"endTime":2217.779,"body":"Next time you get a chance to look at the full moon, you'll see the"},{"startTime":2217.779,"endTime":2218.066,"body":"familiar seas, the dark areas which are are lava, and then the brighter areas on"},{"startTime":2218.066,"endTime":2223.805,"body":"the moon, which are the highlands."},{"startTime":2224.545,"endTime":2229.539,"body":"And on the whole, those are older areas, but where are crater is punched into"},{"startTime":2229.539,"endTime":2230.205,"body":"the surface."},{"startTime":2231.385,"endTime":2235.915,"body":"For example, the large crater at the bottom of this image here, you can see"},{"startTime":2235.915,"endTime":2240.445,"body":"I hope that there are bright rays of material that shoot out across the surface."},{"startTime":2241.385,"endTime":2243.365,"body":"And they're bright because they're fresh."},{"startTime":2244.315,"endTime":2248.821,"body":"They're material that's been dug up from underneath the surface and distributed across a large"},{"startTime":2248.821,"endTime":2250.925,"body":"percentage of the, of the lunar surface."},{"startTime":2251.435,"endTime":2256.452,"body":"They're now exposed to particles called cosmic rays, which come from the sun, but also"},{"startTime":2256.452,"endTime":2258.125,"body":"come from the galactic environment."},{"startTime":2258.385,"endTime":2261.405,"body":"And these high energy particles hit the surface of the moon all the time."},{"startTime":2262.185,"endTime":2266.685,"body":"We are protected down here on earth for the most part by our magnetic field."},{"startTime":2267.025,"endTime":2271.551,"body":"But on the moon, uh, the surface is exposed to this cosmic rays and over"},{"startTime":2271.551,"endTime":2273.965,"body":"time, over millions of years, they will darken."},{"startTime":2274.545,"endTime":2280.007,"body":"Now UA must have been exposed to cosmic rays as it traveled through the galaxy,"},{"startTime":2280.007,"endTime":2283.285,"body":"perhaps for billions of years before it reached us."},{"startTime":2283.595,"endTime":2289.231,"body":"They would've had the effect of getting of exciting and getting rid of water or,"},{"startTime":2289.231,"endTime":2293.365,"body":"um, other volatiles carbon monoxide carbon dioxide from the outer layer."},{"startTime":2293.905,"endTime":2299.183,"body":"And so you end up with an object, which is an icy core with a"},{"startTime":2299.183,"endTime":2299.535,"body":"crispy crust around it, a kind of celestial magnum, uh, if you like, without the"},{"startTime":2299.535,"endTime":2305.165,"body":"stick obviously."},{"startTime":2305.625,"endTime":2309.845,"body":"Um, they, uh, there's a marketing opportunity in there somewhere."},{"startTime":2309.955,"endTime":2312.325,"body":"They will tell the Gresham that we need our own ice creams."},{"startTime":2312.545,"endTime":2315.165,"body":"Uh, anyway, you get so, so this is the idea."},{"startTime":2315.165,"endTime":2316.645,"body":"So it's a hidden comet."},{"startTime":2317.265,"endTime":2321.615,"body":"And so when it comes into the solar system and warms up, you may get"},{"startTime":2321.615,"endTime":2324.805,"body":"less activity than expected, but you may still get these jets."},{"startTime":2325.465,"endTime":2329.781,"body":"And so we wouldn't have seen the activity 'cause it wasn't dramatic enough for even"},{"startTime":2329.781,"endTime":2330.645,"body":"our largest telescopes."},{"startTime":2330.825,"endTime":2332.645,"body":"But you can get this accelerating effect."},{"startTime":2332.745,"endTime":2335.125,"body":"Or if you don't like that idea, we have others."},{"startTime":2335.785,"endTime":2340.719,"body":"Um, there's a group of, uh, astronomers led by Darryl Seggerman who think that, who"},{"startTime":2340.719,"endTime":2345.325,"body":"published papers like this one that claim that perhaps it was made of hydrogen."},{"startTime":2345.825,"endTime":2350.693,"body":"So perhaps it was a hydrogen iceberg that formed somewhere like the Orion Nebula in"},{"startTime":2350.693,"endTime":2352.965,"body":"one of these dark star forming nurseries."},{"startTime":2353.505,"endTime":2355.645,"body":"Um, and has traveled through the galaxy."},{"startTime":2355.665,"endTime":2358.325,"body":"And the point here is that you can heat hydrogen up."},{"startTime":2358.385,"endTime":2364.885,"body":"You would've got these jets of material without um, us being able to detect it."},{"startTime":2364.945,"endTime":2367.445,"body":"So you can, you could sort of sneak away in this way personally."},{"startTime":2367.525,"endTime":2373.337,"body":"I think dehydrated comet, icy shell, crispy shell and IC center is the way to"},{"startTime":2373.337,"endTime":2373.725,"body":"go."},{"startTime":2374.225,"endTime":2379.25,"body":"Um, but there are other arguments and that's all we know about Ur that's very"},{"startTime":2379.25,"endTime":2383.605,"body":"satisfying, this lecture because we will never know anything else about this object."},{"startTime":2384.505,"endTime":2385.765,"body":"We can't go and chase it."},{"startTime":2385.795,"endTime":2387.765,"body":"It's gone too quickly and too far."},{"startTime":2388.305,"endTime":2393.458,"body":"Um, it's lost to our telescopes and very soon we won't even have the accurate"},{"startTime":2393.458,"endTime":2393.802,"body":"accuracy to go and chase it, even if we, we wanted to in the future,"},{"startTime":2393.802,"endTime":2394.145,"body":"if we invent, I dunno, the lin top drive that can go close to the"},{"startTime":2394.145,"endTime":2394.489,"body":"speed of light, we won't know where it is interesting though, and I think probably"},{"startTime":2394.489,"endTime":2394.833,"body":"luckily for all of our sanity when we're arguing, uh, about whether this first interstellar"},{"startTime":2394.833,"endTime":2395.176,"body":"visitor, uh, really is an alien spacecraft or not, we have been visited by a"},{"startTime":2395.176,"endTime":2419.915,"body":"second interloper."},{"startTime":2420.785,"endTime":2427.166,"body":"This is a humble space telescope image of an object called Comet Borisov, which is"},{"startTime":2427.166,"endTime":2430.995,"body":"discovered in August, 2019, um, by a remarkable astronomer."},{"startTime":2430.995,"endTime":2438.583,"body":"Borisov is a, a technician, uh, at a large observatory, um, uh, in um, Kazakhstan"},{"startTime":2438.583,"endTime":2439.595,"body":"I believe."},{"startTime":2440.415,"endTime":2443.275,"body":"Um, but in his spare time he's an astrophotographer."},{"startTime":2443.575,"endTime":2447.475,"body":"And so not during his day job, but in his night job, I guess as"},{"startTime":2447.475,"endTime":2447.735,"body":"an imager of the skies, he discovered this comet, which turned out to be on"},{"startTime":2447.735,"endTime":2452.675,"body":"a similar trajectory to ."},{"startTime":2452.675,"endTime":2454.235,"body":"It's come from outside the solar system."},{"startTime":2454.655,"endTime":2456.035,"body":"It traveled through the solar system."},{"startTime":2456.895,"endTime":2461.995,"body":"Um, and it, this, this image is taken when it's about 300 million kilometers away."},{"startTime":2462.815,"endTime":2466.286,"body":"And I should say the thing on the left here, that's a galaxy, it just"},{"startTime":2466.286,"endTime":2467.675,"body":"happens to be in the background."},{"startTime":2468.215,"endTime":2471.515,"body":"Um, but the blue thing is a comet."},{"startTime":2471.975,"endTime":2473.355,"body":"As you can see, it's got a tail."},{"startTime":2473.815,"endTime":2476.755,"body":"Uh, it's behaving much more like a normal comet."},{"startTime":2477.215,"endTime":2481.555,"body":"So we know that we can get normal in stellar objects as well."},{"startTime":2481.625,"endTime":2483.555,"body":"Borisov is exactly what was predicted."},{"startTime":2483.555,"endTime":2487.155,"body":"It had an interesting encounter with the solar system over time."},{"startTime":2487.605,"endTime":2490.995,"body":"These are images of the nucleus, the center of the comet."},{"startTime":2490.995,"endTime":2495.745,"body":"And you can see on March the 28th, it seemed to split up into two"},{"startTime":2495.745,"endTime":2497.645,"body":"pieces, a few hundred kilometers apart."},{"startTime":2497.955,"endTime":2502.085,"body":"This is typical of comets that get too close to the sun and break up."},{"startTime":2502.545,"endTime":2506.405,"body":"And so we have an icy visitor from another solar system."},{"startTime":2506.705,"endTime":2511.568,"body":"And if you think about the geometry of the solar system that I showed you"},{"startTime":2511.568,"endTime":2511.893,"body":"earlier, which has that alt cloud, that reservoir of comics in the outer solar system,"},{"startTime":2511.893,"endTime":2512.217,"body":"it makes sense that in stellar objects would be comedy because it's easier to escape"},{"startTime":2512.217,"endTime":2512.541,"body":"the sun's pull if you're already a third of the way to the nearest star"},{"startTime":2512.541,"endTime":2512.865,"body":"than it is if you're the way down here in the inner solar system at"},{"startTime":2512.865,"endTime":2532.645,"body":"the bottom of the gravity."},{"startTime":2532.835,"endTime":2538.591,"body":"Well, so rocky asteroids, which tend to be found near the sun, won't have escaped"},{"startTime":2538.591,"endTime":2542.045,"body":"perhaps lots of these comets on the outskirts do."},{"startTime":2543.345,"endTime":2544.645,"body":"So we now have two of these things."},{"startTime":2545.205,"endTime":2550.488,"body":"I was convinced that this morning was gonna see the announcement of a third one,"},{"startTime":2550.488,"endTime":2550.841,"body":"but no, so far, uh, we're still waiting five years on from our second interstellar"},{"startTime":2550.841,"endTime":2556.125,"body":"object."},{"startTime":2556.505,"endTime":2561.821,"body":"But actually there are clues in our solar system that suggest that these things are"},{"startTime":2561.821,"endTime":2562.885,"body":"very common indeed."},{"startTime":2563.745,"endTime":2568.61,"body":"And the first set of clues, the most important ones come from that outer edge"},{"startTime":2568.61,"endTime":2571.205,"body":"of the solar system where, uh, Pluto lives."},{"startTime":2571.785,"endTime":2575.631,"body":"Um, Pluto of course definitely not a planet, as I've mentioned in all of my"},{"startTime":2575.631,"endTime":2578.965,"body":"lectures so far, much to the distress of at least three people online."},{"startTime":2579.305,"endTime":2583.845,"body":"But it's not a, it's not not a planet because it's not interesting."},{"startTime":2584.275,"endTime":2586.085,"body":"Like we didn't decide it was boring."},{"startTime":2586.185,"endTime":2591.504,"body":"In fact, this image from the New Horizons probe, which flew past it in 2014,"},{"startTime":2591.504,"endTime":2595.405,"body":"showed that it was much more interesting, uh, than we thought."},{"startTime":2595.555,"endTime":2597.605,"body":"It's a world with some differentiation."},{"startTime":2597.865,"endTime":2602.325,"body":"It has this heart-shaped plane of water, ice, now known as Sputnik ple pita."},{"startTime":2602.585,"endTime":2606.125,"body":"It actually has mounts of water, ice frozen solid."},{"startTime":2606.185,"endTime":2611.525,"body":"It has these dark, uh, patches actually rather similar to the color of Uma."},{"startTime":2611.625,"endTime":2617.871,"body":"And it has a complex interaction with, uh, its large moon charan, but it is"},{"startTime":2617.871,"endTime":2623.285,"body":"only one of many millions of objects that live in the COI belt."},{"startTime":2623.305,"endTime":2629.515,"body":"Our solar systems outer asteroid belt, this region where planet formation, this process of adding,"},{"startTime":2629.515,"endTime":2629.929,"body":"uh, grains together to form boulders and boulders together to form somehow skyscrapers and skyscrapers"},{"startTime":2629.929,"endTime":2630.343,"body":"together to form planetesimals and then onto planets, didn't proceed as far as it did"},{"startTime":2630.343,"endTime":2644.005,"body":"out in the Coer belt."},{"startTime":2644.755,"endTime":2648.005,"body":"What we have is the rubble of a failed construction project."},{"startTime":2648.455,"endTime":2653.048,"body":"There wasn't enough time to build a planet before the sun got going, uh, and"},{"startTime":2653.048,"endTime":2655.805,"body":"heated up the disc and expelled most of it."},{"startTime":2656.505,"endTime":2661.525,"body":"And the dezens of the Coer belt are interesting in many ways, new horizons."},{"startTime":2661.525,"endTime":2666.406,"body":"When it went past Pluto headed off through the koi belt and the team looked"},{"startTime":2666.406,"endTime":2668.685,"body":"for another object that they can visit."},{"startTime":2668.755,"endTime":2673.886,"body":"They actually used the Hubble Space telescope to look in the direction that their probe"},{"startTime":2673.886,"endTime":2674.228,"body":"was going and tried to discover an object to order something close enough that they"},{"startTime":2674.228,"endTime":2680.045,"body":"could divert to."},{"startTime":2680.045,"endTime":2684.245,"body":"And they found it in a small world called aov, which is only a few,"},{"startTime":2684.245,"endTime":2685.925,"body":"again, a few hundred meters across."},{"startTime":2686.425,"endTime":2690.568,"body":"Um, this is the closest image color image we had of it from that fly"},{"startTime":2690.568,"endTime":2690.845,"body":"by."},{"startTime":2691.305,"endTime":2696.473,"body":"Um, it flew by on New Year's Day 2019 from a distance it looked beautifully"},{"startTime":2696.473,"endTime":2698.885,"body":"like a champagne bottle, which is great."},{"startTime":2699.025,"endTime":2701.365,"body":"As we got closer, it's much more snowman like."},{"startTime":2701.785,"endTime":2706.801,"body":"But the key thing here is that this is not really one object, it's two"},{"startTime":2706.801,"endTime":2707.805,"body":"that have collided."},{"startTime":2707.985,"endTime":2712.555,"body":"You can see there's a bright ring between the two spheres between the snowman's head"},{"startTime":2712.555,"endTime":2713.165,"body":"and body."},{"startTime":2713.585,"endTime":2718.365,"body":"And that's where these two objects have gently drifted into each other and stuck together."},{"startTime":2718.555,"endTime":2719.445,"body":"They're icy."},{"startTime":2719.875,"endTime":2722.485,"body":"It's slushy when you, when you combine the two things."},{"startTime":2723.145,"endTime":2726.205,"body":"And so this is a double object."},{"startTime":2726.705,"endTime":2731.962,"body":"And in fact, lots of the worlds that we know of in the  are"},{"startTime":2731.962,"endTime":2733.365,"body":"binary rather than solitary."},{"startTime":2733.615,"endTime":2738.544,"body":"Pluto even has its moon charan, which is much closer in mass and size to"},{"startTime":2738.544,"endTime":2740.845,"body":"Pluto than any of the major planets."},{"startTime":2740.845,"endTime":2744.52,"body":"The next one down is the earth moon, but uh, Pluto and Charan are much"},{"startTime":2744.52,"endTime":2744.765,"body":"closer."},{"startTime":2745.385,"endTime":2749.485,"body":"Big things like Eris, uh, another of the large co objects are double."},{"startTime":2749.865,"endTime":2754.469,"body":"Um, many of the small worlds seem to be, and of course the comets like"},{"startTime":2754.469,"endTime":2756.925,"body":"67 p Cher Garca that live out there."},{"startTime":2757.385,"endTime":2760.645,"body":"Um, this could well be a double object as well."},{"startTime":2760.645,"endTime":2762.845,"body":"It looks a lot like aov."},{"startTime":2763.945,"endTime":2768.645,"body":"And so somehow we formed these binary or double worlds."},{"startTime":2769.025,"endTime":2774.182,"body":"And the best explanation for that is that the Coyer belt was once a thousand"},{"startTime":2774.182,"endTime":2776.245,"body":"times denser than it is today."},{"startTime":2776.475,"endTime":2781.176,"body":"Instead of having a few percent of the total mass of the earth spread out"},{"startTime":2781.176,"endTime":2781.489,"body":"amongst these bodies, we might have had six or seven earth maths worth of stuff"},{"startTime":2781.489,"endTime":2787.445,"body":"out in the solar system."},{"startTime":2788.465,"endTime":2789.405,"body":"So where did it go?"},{"startTime":2789.995,"endTime":2791.725,"body":"Well, we have a theory for that as well."},{"startTime":2792.185,"endTime":2796.205,"body":"We have to abandon the idea that our solar system is a nice stable place."},{"startTime":2796.675,"endTime":2801.925,"body":"This is a simulation of the first billion years of our solar system's history."},{"startTime":2801.925,"endTime":2805.005,"body":"And we are looking here at the outer solar system."},{"startTime":2805.585,"endTime":2809.953,"body":"So the rings of the orbit of the four giant planets, Jupiter, Saturn, Uranus, and"},{"startTime":2809.953,"endTime":2810.245,"body":"Neptune."},{"startTime":2810.465,"endTime":2813.365,"body":"And the green things are the COI about objects that are left over."},{"startTime":2813.905,"endTime":2818.605,"body":"So if I run this, uh, the time is in the top in millions of"},{"startTime":2818.605,"endTime":2822.365,"body":"years, the first billion years, few, few hundred million years, nothing happens."},{"startTime":2822.725,"endTime":2824.085,"body":"Everything's nice and stable."},{"startTime":2824.105,"endTime":2827.045,"body":"You can see the planets are moving about very slightly."},{"startTime":2827.105,"endTime":2829.725,"body":"That's because of their mutual gravitational attraction."},{"startTime":2829.795,"endTime":2834.921,"body":"Jupiter's pulling on Saturn sa, Saturn, Uranus and Neptune have a collective effect on Jupiter"},{"startTime":2834.921,"endTime":2839.365,"body":"u and Neptune tract, but nothing really happens for 600, 700 million years."},{"startTime":2839.385,"endTime":2844.68,"body":"But in this simulation, when we reach about 800 million years and we'll slow it"},{"startTime":2844.68,"endTime":2846.445,"body":"down, a resonance is achieved."},{"startTime":2846.625,"endTime":2850.805,"body":"Saturn and Jupiter start lining up and all hell breaks loose."},{"startTime":2851.585,"endTime":2855.777,"body":"So what happens is Jupiter and Saturn get themselves into a pattern where they're, they"},{"startTime":2855.777,"endTime":2856.057,"body":"line up in the same part of their orbit every few orbits, and that gives"},{"startTime":2856.057,"endTime":2862.765,"body":"a regular kick to the rest of the solar system."},{"startTime":2862.765,"endTime":2867.435,"body":"So it's like if you're pushing somebody on a swing, if you're already always push"},{"startTime":2867.435,"endTime":2867.746,"body":"at the same point, you get a much better, uh, response from the swing that"},{"startTime":2867.746,"endTime":2874.285,"body":"causes havoc in the out soul system."},{"startTime":2874.285,"endTime":2875.645,"body":"Jupiter tends to move inward."},{"startTime":2875.645,"endTime":2876.805,"body":"Saturn tends to move outwards."},{"startTime":2877.125,"endTime":2878.805,"body":"Uranus and Neptune swapped places."},{"startTime":2879.125,"endTime":2881.045,"body":"I dunno if anyone noticed that in the animation."},{"startTime":2881.385,"endTime":2885.405,"body":"And the COI belt is scattered out into the galaxy."},{"startTime":2885.985,"endTime":2890.23,"body":"And so what we see in our COI belt, Pluto and Friends are the survivors"},{"startTime":2890.23,"endTime":2891.645,"body":"of this most dramatic event."},{"startTime":2892.225,"endTime":2896.405,"body":"We think that our soul system donated 10 to the 16."},{"startTime":2897.185,"endTime":2897.925,"body":"So what's that?"},{"startTime":2897.945,"endTime":2904.005,"body":"That's something like, let's say a hundred million billion objects to the galaxy."},{"startTime":2904.465,"endTime":2910.477,"body":"And if every other solar system does that, objects like ua, MUA are the most"},{"startTime":2910.477,"endTime":2914.485,"body":"common macroscopic objects, the most common things in the galaxy."},{"startTime":2915.655,"endTime":2919.045,"body":"There are billions and billions and billions of them out there."},{"startTime":2919.475,"endTime":2921.845,"body":"They're passing throughout solar system all the time."},{"startTime":2921.965,"endTime":2926.901,"body":"Calculations show with a large error bar that there's almost always something the size of"},{"startTime":2926.901,"endTime":2929.205,"body":"Ur muah within the orbit of Neptune."},{"startTime":2929.225,"endTime":2934.36,"body":"We are just extraordinarily bad at spotting them because they're small, they're dark, and they"},{"startTime":2934.36,"endTime":2935.045,"body":"move fast."},{"startTime":2935.785,"endTime":2938.525,"body":"And so we shouldn't really be surprised that we saw Ur muah."},{"startTime":2938.825,"endTime":2942.765,"body":"We should be surprised that we've only found two of these things."},{"startTime":2944.305,"endTime":2947.888,"body":"And this is the answer to the mystery that I left open at the start"},{"startTime":2947.888,"endTime":2948.605,"body":"of the talk."},{"startTime":2949.025,"endTime":2953.485,"body":"How do we jump from things that are bolder sized to skyscraper sized?"},{"startTime":2953.675,"endTime":2958.365,"body":"Well, AMU few hundred meters across is a flying skyscraper."},{"startTime":2959.235,"endTime":2965.013,"body":"That disc of material around the young star will be peppered with these interstellar objects"},{"startTime":2965.013,"endTime":2967.325,"body":"flying through from other solar systems."},{"startTime":2967.985,"endTime":2973.713,"body":"And Suzanne Felner and Michelle Banister have proposed the idea that the seeds of planet"},{"startTime":2973.713,"endTime":2976.005,"body":"formation come from these interstellar objects."},{"startTime":2976.865,"endTime":2982.658,"body":"Uh, get started quick way of building a solar system, the equivalent of a ready"},{"startTime":2982.658,"endTime":2983.045,"body":"meal."},{"startTime":2983.405,"endTime":2988.571,"body":"I guess if you start with the disc capturing these objects, then you can quickly"},{"startTime":2988.571,"endTime":2989.605,"body":"grow a planet."},{"startTime":2991.405,"endTime":2991.895,"body":"Alright?"},{"startTime":2991.915,"endTime":2994.295,"body":"You have to form planet somewhere the slow way."},{"startTime":2994.735,"endTime":2996.215,"body":"Somebody has to do it the hard way."},{"startTime":2996.605,"endTime":3001.735,"body":"Somewhere in the dim distant past of the Milky Way, there was a star with"},{"startTime":3001.735,"endTime":3002.077,"body":"a long-lived disc that could have formed planets, which would then have scattered 10 to"},{"startTime":3002.077,"endTime":3008.575,"body":"the 16 in stellar objects."},{"startTime":3008.665,"endTime":3010.895,"body":"Those would've kickstarted more planet formation."},{"startTime":3010.895,"endTime":3016.499,"body":"And suddenly you have this runaway process that spreads very quickly through the galaxy and"},{"startTime":3016.499,"endTime":3016.873,"body":"allows us to form planets rapidly and makes it so that we live in a"},{"startTime":3016.873,"endTime":3026.215,"body":"universe where planets are common and there are worlds to explore."},{"startTime":3026.795,"endTime":3033.333,"body":"So though UA isn't, I promise it's not an alien spacecraft, there's too many of"},{"startTime":3033.333,"endTime":3034.205,"body":"the things."},{"startTime":3034.345,"endTime":3039.822,"body":"And the fact we found two and we'll find more tells us that it's still,"},{"startTime":3039.822,"endTime":3040.187,"body":"I think, has a message for us, which is that what's happened here, that in"},{"startTime":3040.187,"endTime":3040.552,"body":"explaining our solar system, we've got no choice but to consider ourselves as part of"},{"startTime":3040.552,"endTime":3055.525,"body":"a galaxy connected by these scouts, these messengers that wander between the stars."},{"startTime":3056.455,"endTime":3057.245,"body":"Thank you very much"},{"startTime":3061.345,"endTime":3062.325,"body":"Now by my book,"},{"startTime":3069.215,"endTime":3069.565,"body":"Chris."},{"startTime":3069.565,"endTime":3070.165,"body":"Thank you very much."},{"startTime":3070.165,"endTime":3071.885,"body":"And let's all just take a moment"},{"startTime":3073.345,"endTime":3073.805,"body":"Is on there."},{"startTime":3073.805,"endTime":3074.685,"body":"You see it's on the cover."},{"startTime":3074.785,"endTime":3076.725,"body":"So it is relevant in the, in the blue."},{"startTime":3077.155,"endTime":3077.765,"body":"Fantastic."},{"startTime":3077.915,"endTime":3078.605,"body":"Well, wow."},{"startTime":3078.715,"endTime":3083.365,"body":"Well we've had it all, we've had a world that's not a planet, but uh,"},{"startTime":3083.365,"endTime":3085.845,"body":"it's sort of like one of those things."},{"startTime":3085.845,"endTime":3088.759,"body":"Like if it looks like a planet and it smells like a planet, why is"},{"startTime":3088.759,"endTime":3089.925,"body":"it not a planet too small?"},{"startTime":3090.235,"endTime":3090.885,"body":"Okay, it's too small."},{"startTime":3090.935,"endTime":3091.285,"body":"We're"},{"startTime":3091.285,"endTime":3092.365,"body":"Gonna keep coming back to Pluto."},{"startTime":3092.685,"endTime":3094.605,"body":"I I promise to get it into every talk now."},{"startTime":3095.165,"endTime":3095.405,"body":"Excellent."},{"startTime":3095.545,"endTime":3098.925,"body":"And then we've also had, um, a Flying Magnum that was, that was a highlight."},{"startTime":3098.945,"endTime":3101.685,"body":"So loads to loads of those to talk about."},{"startTime":3101.835,"endTime":3102.685,"body":"Lots of questions."},{"startTime":3103.225,"endTime":3108.681,"body":"Um, and I think actually, right, okay, let's just hit the alien issue \u003claugh\u003e right"},{"startTime":3108.681,"endTime":3109.045,"body":"now."},{"startTime":3109.405,"endTime":3113.04,"body":"'cause um, I'm not gonna lie to you Chris, that is a feature and quite"},{"startTime":3113.04,"endTime":3113.525,"body":"a lot."},{"startTime":3113.935,"endTime":3114.285,"body":"Hello."},{"startTime":3114.345,"endTime":3115.485,"body":"The internet of these,"},{"startTime":3115.705,"endTime":3116.445,"body":"Of these questions."},{"startTime":3116.625,"endTime":3119.829,"body":"So just to pick up on that last point you made, and I think sort"},{"startTime":3119.829,"endTime":3121.325,"body":"of collect some of these questions together."},{"startTime":3122.265,"endTime":3126.445,"body":"So obviously there's a degree to which some in humor, some not."},{"startTime":3126.465,"endTime":3128.565,"body":"So in humor there's a disappointment."},{"startTime":3128.675,"endTime":3131.725,"body":"This isn't an alien, this isn't, um, Arthur Clark's vision."},{"startTime":3131.755,"endTime":3132.805,"body":"This isn't a spaceship."},{"startTime":3133.345,"endTime":3137.311,"body":"But actually, um, I thought it was really interesting how you said, well, if we"},{"startTime":3137.311,"endTime":3137.575,"body":"can get past some of our expectations, not just about what we should be looking"},{"startTime":3137.575,"endTime":3137.84,"body":"for, what we should be seeing or what we would like to see, but actually"},{"startTime":3137.84,"endTime":3138.104,"body":"it's really exciting to, like the, the implications of something like this could actually be"},{"startTime":3138.104,"endTime":3151.325,"body":"really enormous for how we consider the universe."},{"startTime":3151.425,"endTime":3151.965,"body":"Is that about"},{"startTime":3152.225,"endTime":3152.685,"body":"That's right."},{"startTime":3152.685,"endTime":3156.932,"body":"And I think one of the things Ur taught me, and I've changed what I'm"},{"startTime":3156.932,"endTime":3157.215,"body":"working on to, to pay attention to, to things like this is that we should"},{"startTime":3157.215,"endTime":3163.445,"body":"be ready to be surprised by the universe."},{"startTime":3163.475,"endTime":3165.285,"body":"This is our solar system, right?"},{"startTime":3165.295,"endTime":3166.885,"body":"We've lived in it for a while."},{"startTime":3167.295,"endTime":3170.165,"body":"We've sent probes into it, we've mapped it, yes."},{"startTime":3170.185,"endTime":3170.525,"body":"All right."},{"startTime":3170.525,"endTime":3174.365,"body":"We find new asteroids daily, there's a catalog of a few million of them."},{"startTime":3175.265,"endTime":3184.096,"body":"Um, this is our backyard and yet Umu tells us that we can be caught"},{"startTime":3184.096,"endTime":3184.685,"body":"unawares."},{"startTime":3184.685,"endTime":3186.525,"body":"That the unexpected can still happen."},{"startTime":3186.795,"endTime":3191.074,"body":"That actually in the solar system there may be types of object we haven't thought"},{"startTime":3191.074,"endTime":3191.645,"body":"of yet."},{"startTime":3192.135,"endTime":3196.885,"body":"There may be a population of hidden comets in the distance solar system."},{"startTime":3196.885,"endTime":3200.667,"body":"There may be things in unusual orbits, there may be an alien spacecraft lurking between"},{"startTime":3200.667,"endTime":3202.685,"body":"Mars and Jupiter that we have at value."},{"startTime":3202.785,"endTime":3203.405,"body":"We don't know."},{"startTime":3203.905,"endTime":3208.885,"body":"And so particularly I'm working on this thing, this is the Vera Rubbin observatory."},{"startTime":3209.315,"endTime":3212.843,"body":"This is going to do a new survey of the sky, which we'll find in"},{"startTime":3212.843,"endTime":3214.725,"body":"its first year, we think 6 million asteroids."},{"startTime":3216.105,"endTime":3219.325,"body":"And one response to that is to say, great, we've got lots more asteroids."},{"startTime":3219.345,"endTime":3223.714,"body":"The other is say, okay, which 10 of those are most unusual and what are"},{"startTime":3223.714,"endTime":3226.045,"body":"their properties and what do they tell us?"},{"startTime":3226.545,"endTime":3230.327,"body":"Now my guess is that they'll tell us about details of how the solar system"},{"startTime":3230.327,"endTime":3233.605,"body":"formed and uh, how it perhaps has evolved in the 4 billion years."},{"startTime":3233.705,"endTime":3239.285,"body":"But we should consider the possibility of looking for what we call techno signatures."},{"startTime":3239.345,"endTime":3240.885,"body":"So spacecraft in there as well."},{"startTime":3241.185,"endTime":3244.045,"body":"But we can do that by looking for weird astronomical things."},{"startTime":3244.425,"endTime":3249.208,"body":"And only when we've ruled out an astronomical origin, then I'll turn around and say,"},{"startTime":3249.208,"endTime":3250.165,"body":"okay, maybe, maybe."},{"startTime":3250.265,"endTime":3254.941,"body":"But for amu muah, there, there's no evidence it's anything other than a really fascinating"},{"startTime":3254.941,"endTime":3255.565,"body":"astronomical object."},{"startTime":3256.615,"endTime":3256.965,"body":"Great."},{"startTime":3257.185,"endTime":3259.885,"body":"So you're not quite, you're not taking aliens away from off."},{"startTime":3259.885,"endTime":3261.445,"body":"They're not off the table completely."},{"startTime":3261.635,"endTime":3261.925,"body":"Nope."},{"startTime":3261.955,"endTime":3263.445,"body":"They're just slightly to the side."},{"startTime":3263.785,"endTime":3264.525,"body":"And if we"},{"startTime":3264.525,"endTime":3265.925,"body":"Well, they, they shouldn't be your first."},{"startTime":3266.125,"endTime":3267.685,"body":"I mean, I think where I, I disagree."},{"startTime":3267.705,"endTime":3271.312,"body":"So, so a avy Loeb who, who is the advocate of these things would say"},{"startTime":3271.312,"endTime":3271.552,"body":"that they should be the first thing we think of that when we see something"},{"startTime":3271.552,"endTime":3277.805,"body":"unusual, we should say, is this aliens before we do anything else?"},{"startTime":3277.945,"endTime":3278.885,"body":"And that's fine."},{"startTime":3278.885,"endTime":3280.525,"body":"It doesn't really get me very far."},{"startTime":3281.245,"endTime":3286.771,"body":"'cause the answer is always maybe, uh, what I have to do is see if"},{"startTime":3286.771,"endTime":3287.139,"body":"there's another alternative explanation first and then get driven to the, um, more extreme or,"},{"startTime":3287.139,"endTime":3295.245,"body":"or or more unusual claims at the end."},{"startTime":3295.435,"endTime":3295.725,"body":"Okay."},{"startTime":3295.725,"endTime":3299.645,"body":"So if we maybe challenge 'em of our expectations or maybe aspirations, then we might"},{"startTime":3299.645,"endTime":3303.565,"body":"be able to ask different kinds of questions, which is always really interesting for science."},{"startTime":3303.945,"endTime":3306.365,"body":"So let's take a question from the floor,"},{"startTime":3307.285,"endTime":3308.325,"body":"A couple of observations."},{"startTime":3308.945,"endTime":3314.325,"body":"The, the, uh, those two objects, one eye and two eye, um, remain unique."},{"startTime":3315.665,"endTime":3320.977,"body":"Um, of course when the Vera Rubian telescope starts, starts operating, then we may find"},{"startTime":3320.977,"endTime":3321.331,"body":"a lot if we don't, and in particular in the case of the, the more"},{"startTime":3321.331,"endTime":3321.685,"body":"mysterious one, which is, which is one eye  then, given that it is, and"},{"startTime":3321.685,"endTime":3322.039,"body":"I'm told this by people who understand these things, it's is in principle possible to"},{"startTime":3322.039,"endTime":3338.685,"body":"send a mission to it?"},{"startTime":3339.985,"endTime":3341.565,"body":"Um, should we do so?"},{"startTime":3342.315,"endTime":3342.605,"body":"Yeah."},{"startTime":3342.705,"endTime":3343.925,"body":"So, so there a few questions there."},{"startTime":3343.925,"endTime":3348.008,"body":"So yeah, so with the Rubin telescope, we think we're gonna find about a hundred"},{"startTime":3348.008,"endTime":3348.281,"body":"of these interstellar objects, but that number could be 10 or it could be a"},{"startTime":3348.281,"endTime":3352.365,"body":"thousand."},{"startTime":3352.425,"endTime":3354.725,"body":"It depends slightly on how optimistic we're feeling."},{"startTime":3355.185,"endTime":3358.885,"body":"Um, because we are trying to extrapolate from two, I should say we've work."},{"startTime":3359.075,"endTime":3362.045,"body":"I've got PhD student, Matthew Hopkins who's been working on this."},{"startTime":3362.145,"endTime":3365.918,"body":"And um, we can predict what these things will be like based on what we"},{"startTime":3365.918,"endTime":3366.925,"body":"know about the galaxy."},{"startTime":3367.225,"endTime":3371.516,"body":"And we think that even if we find 50 of them, UR more may still"},{"startTime":3371.516,"endTime":3373.805,"body":"look odd because it is on the extreme."},{"startTime":3373.875,"endTime":3375.285,"body":"It's not unusual."},{"startTime":3375.635,"endTime":3378.045,"body":"It's unusual, but it's not a complete outlier."},{"startTime":3378.065,"endTime":3381.98,"body":"So we shouldn't be surprised if the first 10 that we find all look like"},{"startTime":3381.98,"endTime":3383.285,"body":"Borisov, they look like comets."},{"startTime":3383.585,"endTime":3387.23,"body":"We will find a population of the, we think we'll find a population of like"},{"startTime":3387.23,"endTime":3388.445,"body":"things, but we don't know."},{"startTime":3388.465,"endTime":3389.325,"body":"So we'll have to find out."},{"startTime":3389.325,"endTime":3393.981,"body":"There's also a NASA mission, um, that's again looking for near earth asteroids that will"},{"startTime":3393.981,"endTime":3397.085,"body":"launch in 2028, which we'll find lots of these things."},{"startTime":3397.085,"endTime":3400.811,"body":"So in 10 years time we should have a few hundred and then we can"},{"startTime":3400.811,"endTime":3401.805,"body":"could say something sensible."},{"startTime":3402.185,"endTime":3404.885,"body":"Can, should we, should we launch Mission Tou?"},{"startTime":3404.885,"endTime":3405.405,"body":"If we could."},{"startTime":3405.525,"endTime":3407.965,"body":"I definitely would be fascinating."},{"startTime":3407.965,"endTime":3410.125,"body":"There are all sorts of questions about it as you've seen."},{"startTime":3410.505,"endTime":3415.285,"body":"Um, I, for a sensible budget, um, and a sensible timescale."},{"startTime":3415.485,"endTime":3416.725,"body":"I don't think we can get there in time."},{"startTime":3416.925,"endTime":3420.667,"body":"'cause the problem is we only watched it for a few months and so the"},{"startTime":3420.667,"endTime":3422.165,"body":"error on its trajectory is large."},{"startTime":3422.785,"endTime":3426.098,"body":"And so I think we're close to the point now that even if you had"},{"startTime":3426.098,"endTime":3426.319,"body":"all the money in the world and you could launch with our best Rocket a"},{"startTime":3426.319,"endTime":3432.725,"body":"satellite right now, you wouldn't necessarily find it even if you could hit the speed."},{"startTime":3432.745,"endTime":3434.325,"body":"So I think it's gone sadly."},{"startTime":3434.565,"endTime":3435.045,"body":"I think that's true."},{"startTime":3435.445,"endTime":3437.485,"body":"I would suggest you look at something called Project."},{"startTime":3438.195,"endTime":3438.605,"body":"Yeah, yeah."},{"startTime":3438.605,"endTime":3439.325,"body":"I know about, yeah."},{"startTime":3439.335,"endTime":3439.765,"body":"Thank you."},{"startTime":3439.885,"endTime":3441.685,"body":"I, I-I-I-I-I love their optimism."},{"startTime":3442.285,"endTime":3444.365,"body":"\u003claugh\u003e, I'm gonna take one more question,"},{"startTime":3444.585,"endTime":3447.445,"body":"Should say, by the way, we're going to do another episode of the Gresham podcast."},{"startTime":3447.905,"endTime":3448.485,"body":"Any questions?"},{"startTime":3448.625,"endTime":3450.125,"body":"So we can answer more questions?"},{"startTime":3450.185,"endTime":3452.645,"body":"So do send them in and I promise I'll get to them."},{"startTime":3452.645,"endTime":3452.885,"body":"Yeah."},{"startTime":3453.305,"endTime":3453.525,"body":"Um,"},{"startTime":3453.595,"endTime":3459.27,"body":"What are the chances of New Horizon finding further objects and would we find out"},{"startTime":3459.27,"endTime":3460.405,"body":"important things if"},{"startTime":3460.405,"endTime":3460.725,"body":"It did?"},{"startTime":3460.755,"endTime":3461.805,"body":"Yeah, it's a good question."},{"startTime":3461.985,"endTime":3466.272,"body":"So, um, the New Horizons team, um, spent a lot of time using Hubble, looking"},{"startTime":3466.272,"endTime":3468.845,"body":"for a third object that they can go to."},{"startTime":3468.845,"endTime":3472.085,"body":"They don't have much fuel left on board, so they can't really divert."},{"startTime":3472.505,"endTime":3476.605,"body":"So they need to find something, um, in the direct, direct line."},{"startTime":3476.625,"endTime":3478.285,"body":"And they've more or less given up on that."},{"startTime":3478.475,"endTime":3484.306,"body":"What they're doing instead is they, they, it does have a telescope on board, so"},{"startTime":3484.306,"endTime":3487.805,"body":"it's doing observations of, uh, relatively nearby  objects."},{"startTime":3487.805,"endTime":3489.885,"body":"After all, it's much closer to them than we are."},{"startTime":3490.065,"endTime":3494.685,"body":"And so we're actually building up a library of images taken from quite a long"},{"startTime":3494.685,"endTime":3497.765,"body":"distance, but much less than we have of these objects."},{"startTime":3497.765,"endTime":3500.485,"body":"So it's sort of become an astronomy satellite."},{"startTime":3500.745,"endTime":3504.485,"body":"And it's also monitoring the, the effect of the sun on the outer solar system."},{"startTime":3504.505,"endTime":3507.617,"body":"So it's still doing science, but I don't think we'll get another fly by like"},{"startTime":3507.617,"endTime":3509.485,"body":"we did with Aof, unless we get really lucky."},{"startTime":3510.875,"endTime":3511.165,"body":"Okay."},{"startTime":3511.375,"endTime":3511.725,"body":"Great."},{"startTime":3511.955,"endTime":3513.245,"body":"Well, thank you so much."},{"startTime":3513.275,"endTime":3515.045,"body":"There's lots and lots of questions."},{"startTime":3515.045,"endTime":3516.365,"body":"Unfortunately we're out of time."},{"startTime":3516.365,"endTime":3520.865,"body":"But as Chris has just kindly volunteered to do another, any further questions podcast, look"},{"startTime":3520.865,"endTime":3521.765,"body":"out for that."},{"startTime":3521.945,"endTime":3524.685,"body":"And I'm sure if your question's on here, you'll get to it."},{"startTime":3524.835,"endTime":3526.125,"body":"Even if it is about"},{"startTime":3526.125,"endTime":3527.205,"body":"Aliens, it's still not aliens."},{"startTime":3527.345,"endTime":3527.645,"body":"I'm sorry."},{"startTime":3528.815,"endTime":3529.965,"body":"Chris then taught everyone."}]}