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The Sky at Night - Exoplanets
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00:00Let me tell you about one of the youngest and most exciting areas of astronomy research.
00:05This is a field that is so riddled with diversity and discovery that astronomers are constantly left
00:11going huh huh huh yes it's finally happening everyone we're doing an episode on exoplanets.
00:22Exoplanets are planets outside the solar system so typically planets orbiting any
00:27star rather than the sun but some of them are orphaned and have no star at all so just outsiders
00:32really and honestly the stuff we've been discovering is just constantly challenging
00:37everything we think we know about how planets form and evolve i tell you it is wild out there
00:44in fact it is so compelling that back in 2018 i left my lovely stable job as a secondary school
00:50physics teacher moved to the midlands and embarked on a phd in astrophysics as a mature student
00:56i had to learn gen z slang to get the cool kids to talk to me and lucky for you tonight you're gonna
01:03get a taste of the field i love so much without having to leave your job or even your sofa for
01:09for that matter welcome to the sky at night
01:21so
01:39humanity has been dreaming of finding planets out amongst the stars since we first started staring
01:49into space asking questions and wondering what might be up there waiting to be discovered
01:55how lucky we are to be the generation that gets to answer those questions the first exoplanet around a
02:01normal star was found in 1995 by astronomers watching how a star wobbled this way and that back
02:08and forth pulled by the gravity of a saturn mass planet such giant planets all lie far from the sun
02:16but this one whizzed around its star in just four and a half days no one had expected such a world
02:24and this one discovery spurred on a new generation of planet hunters who wanted to conduct a census
02:30of planets in our galaxy to do so they used a different technique the transit method thousands
02:36of stars are monitored at once looking for the faint dip in brightness that happens when a planet gets in
02:41front of its parent star results from space telescopes like kepler more recently tess have told
02:47us that not only is the galaxy full of planets but that some of them might well be like our own earth
02:54now exactly how earth-like a earth-like planet has to be in order to count as properly earth-like is
03:00open to debate if we assume that life like us needs a planet like ours cozy atmosphere liquid water the
03:08right temperature the results that we have on hand are close to confirming that not only is the milky way full of
03:14worlds but lots of them are possible homes are any of these worlds actually inhabited well astronomers
03:22hope to detect what's called a biosignature a chemical which might indicate the presence of life
03:29a recent paper claimed to have detected a chemical dms in the atmosphere of a neptune-sized world called
03:36k218b now on earth dms is made exclusively by life mostly by microorganisms so this is exciting but the
03:46picture is murky some people think that k280b has a liquid water ocean others that it's a lava world and
03:53those details matter other groups have looked at the same data and found no trace at all of dms and even
04:01if it is there can we be sure that it can't be produced without life in the chemistry of such a
04:06strange world people are doing lab experiments to be sure basically this stuff is hard but in the
04:13meantime don't despair don't worry that we haven't yet found our perfect twin earth but revel instead
04:20in the diversity of worlds that we do know about there are hot jupiters and hot neptunes warm jupiters
04:27of warm neptunes lava worlds earth-like places venus-like planets comet-like planets stripped
04:34core planets diamond worlds planets around young stars planets around old stars planets around pulsars
04:40that make no sense at all there are planets while chris continues his list of amazing planets that have
04:46already been found i'm in germany where a new mission that hopes to find many more is being built
04:57the planet hunter isa's plato spacecraft is set to fly about a million miles to the l2 lagrange point
05:06where it's going to unfoul its nine meter wingspan and settle in for about four years to observe
05:12about 200 000 stars and the exoplanets that orbit them i'm meeting industrial prime project manager
05:19paulo giorba golloma by a model of the spacecraft at the heart of the plato mission is the extraordinary
05:27array of precision engineered high spec cameras two fast cameras at the top are integral for guiding
05:36while the rest focus on monitoring the stars to hunt for exoplanets so talk me through these cameras
05:44they're kind of slightly offset from each other what does that mean plato has 24 nominal cameras
05:49devoted for observation that are divided in four different group of six cameras so we have a
05:54first group here of six cameras second third and fourth so all the cameras or groups are tilted in
06:00a way that you have a overlap of the 24 cameras in the center so in the center field of view of the
06:06spacecraft you will have all the 24 cameras looking to the same star to try to detect any kind of dim on
06:12the liner by grouping the cameras like this plato can obtain a wide field of view covering five
06:20percent of the sky while also getting incredible detail in smaller sections where more cameras overlap
06:29but this requires precision and the extremes of space cause huge engineering challenges
06:36the film our control of a spacecraft like plato is really complicated uh we need to understand that
06:42the central and solar array which is pointing all the time to the sun will rise to up to 160 degrees
06:47Celsius meanwhile the cameras will be around minus 80 degrees Celsius that's kind of specific why that
06:53temperature so in average we are talking about minus 80 degrees Celsius but each camera has been
06:58characterized individually to determine which is the optimum point of operation in terms of focus in
07:04terms of performance of the detectors for this reason so maybe one camera is at minus 79.5 another one is
07:11minus 79.7 so we have a dedicated thermal control camera by camera and we are controlling during the
07:20whole mission that the camera temperature is always at the same point not only because of performance but
07:25also because the temperature of the camera affects also the alignment i i i honestly i'm absolutely blown away
07:30so every single camera has its own little heater keeping it stable and temperature to like a thousandth of a
07:39degree yes incredible what stage is the build up right now where have you got to just last week we
07:47completed the integration or making of the payload which is the 26 cameras and the electronics with the
07:54service model it's a really really precise and challenging activity that involves the participation of
08:00more than 20 people during one week congratulations i mean what a massive milestone to have hit
08:07now obviously for an exoplaneteer like me um this is so exciting in terms of the data we're going to
08:14get but for an engineer like yourself what's it been like so on one side of course it's technical we are
08:20engineers we love challenge but not only this if we consider the number of institutions universities
08:26that has been contributed for the development of the payload it's really for me something that makes me
08:32proud to be in a project it's european okay so now can i see the real thing uh yes we will see it but
08:41please don't touch it yeah don't touch
08:47plato will be the culmination of the work of over 100 organizations from across europe and i don't want
08:54to be the one to mess that up so first it's time to don some pee pee with that done the moment has
09:03arrived what's up
09:11it's so beautiful
09:16on this plane so my heart was racing when i was waiting in the clean room to come out and like yeah
09:23he's a beauty and i was told actually that of the scientists who are going to use plato data
09:31i'm the first one to see it like mated to see it like put together of the exoplaneteers i feel very
09:40privileged to be here this is mind-blowing i am absolutely obsessed all these panels are currently
09:49open because we are in the middle of rooting all the tables and what you see here for example is
09:53the on-board computer and you see also the communication channels or communication panels
09:58yeah the antenna that is behind here
10:05my face hurts i'm barely holding it together from down here but then i was allowed the ultimate view
10:19so i can see all the cameras are they in their positions like have they been aligned yes all of
10:30them are placed integrated tested and aligned george talk to me huh talk to me i can't i'm in love
10:42i could stay here all day
10:43it's incredible to think that in about a year and a half plato will be out there scanning the skies for
10:51new exoplanets
10:57but in the meantime we already have a huge sample of exoplanets to keep us busy
11:02we've got icy worlds and water worlds and ocean worlds and high sea and worlds super earths and
11:11sub-earths super puffs super as we discover these bizarre worlds we've been cataloguing them and plotting
11:18them onto graphs and a puzzling mystery has emerged so far we've found thousands of exoplanets and for the
11:28majority of them we can work out their radii now it turns out that most of them sit between earth
11:34size and neptune size now neptune is three and a half times the size of earth but there's a mystery
11:42to explain further i've got a little demonstration and it involves sweets now each of these jars
11:48represents a distribution of exoplanet size this one is one to one and a half times the size of earth
11:55this one is one and a half to two times the size of earth and this one is two to three and a half
12:01times the size of earth now these sweets represent the exoplanets and we can fill up the jars according
12:07to their sizes now as you can see i think a pattern is emerging but let's put the other exoplanets in
12:22and then i'll explain so now we've distributed all the exoplanets you can see where the mystery lies
12:34we have plenty in this jar we have plenty in this jar but in the one and a half to two times the size
12:40of earth there seems to be a deficit and the mystery is so grand it's been given its own title it's called
12:46the exoplanet radius valley because if you plot this on a graph you get a valley here in the middle
12:59to find out more about this gap i'm being joined by larissa palefort who's been studying this area
13:05and along the way found more than she expected now we're speaking exoplanets we've been doing a
13:15demonstration looking at the radii valley and this is the area of your phd research can you tell us more
13:22so my phd thesis is called characterizing small exoplanets essentially i look at these planets which are
13:29around earth size to work out kind of why we have this gap in the makeup of these planets adding new
13:37sweets into these jars um so that we can learn more about the problem and try and get some answers
13:42okay and i suppose that's it um the sort of more sweets we have the better ones we understand the
13:47distribution and you have a proud position of detecting an exoplanet yourself tell us more about
13:54your exoplanets yes so glieser 12b i co-led the discovery of that planet last year it's an earth
14:01size very temperate planet so it's about 42 degrees celsius on the surface which makes it a very exciting
14:07candidate for follow-up to see yes so almost earth-like i mean 42 is a bit warm but yeah so um we would
14:16classify that as kind of earth-like kind of looking at can liquid water exist on the surface and obviously
14:22at 42 degrees celsius um it could uh but it's hard to say whether the planet is earth-like right now
14:28from the information we have right now we currently only know the radius of the planet so the size of
14:33it um in future we're going to learn more about the mass that's currently being worked on right now
14:38but what we really want to understand is does it have an atmosphere so i have to bring it up life
14:44we don't know about if it has an atmosphere or anything like that but um it just feels quite
14:49exciting that you know potentially there could be life maybe yeah potentially um it's kind of hard to
14:56make a claim like that with kind of the date the way we analyze data right now but um it's definitely
15:00a good candidate for looking at kind of a temperate earth-sized planet um and what ends up evolving on
15:07the surface of that so hopefully maybe it's habitable but we don't know right now hopefully we will
15:12know in the future and i suppose the other exciting thing is it's not that far away so it's actually our
15:17nearest earth-sized temperate transiting planet found today i love the description yeah it's
15:24a bit of a mouthful so near it's 40 light years it's earth size it's about one earth radii it's
15:29temperate it's 42 degrees celsius on its surface and it's transiting so it passes in front of the star
15:34which makes it helpful for observations orbiting a red dwarf star that is just 27 the size of our sun
15:43glieser 12b is a fascinating planet but we still have the radius valley mystery to solve
15:51are there theories out there that might explain why we have this lull yes there are theories um so it's
15:57to do with how planets form and evolve there are a few different mechanisms as to how we think this
16:01might work but the key base theory is that planets start off with atmospheres and through some process
16:07whether it's to do with the star or the way they've formed is that they have their atmospheres stripped
16:11from them and hence they become super earths so there are different mechanisms we haven't been
16:16able to nail down the mechanism yet but essentially it's atmospheric loss okay yes what we think and
16:22this is sort of the transition zone yeah and so they start off here they end up here and then they just
16:26pass through this and so there might not be many out there yeah so theoretically we should see planets
16:31moving through the valley and depending on the exact theory you choose is how long it would take
16:37them to move through the valley so that's how we're going to narrow things down so again it's adding
16:41more sweets to this jar um and seeing how long they stay in that jar for before they jump over
16:47hopefully will help us nail it down well you can't argue with more sweets yeah exactly exactly
16:54we've got planets with clear atmospheres planets where it rains glass planets where it rains
16:59iron hazy planets cloudy planets planets with rings but the planet we really want to find
17:07is one exactly like ours and maybe plato will be the one to find it george has torn herself away from
17:16the spaceship and is sitting down with thomas valashek the isa project manager of the mission
17:22to find out what makes it so special so talk to me about plato's aims what's plato going to achieve
17:29for us so we are really looking for earth-like planets around sun-like stars in what people
17:37call the habitable zone so meaning there might be a possibility of liquid water what's special about
17:43this mission i would say we are a multi telescope mission which is quite different to to the missions
17:50beforehand beforehand we had let's say single telescopes we have 26 cameras on board but also
17:56there we have a blue filter and a red filter on the fast cameras which could give us a hint about
18:02already the atmospheres of these planets now of course these are going to be very impressive cameras
18:07but can you put it in terms i'll understand how many megapixels how does how does it compare to my phone
18:11camera for example you know roughly the size of your phone and then we can talk maybe about the size of
18:19one sensor of one of the cameras which has 20 megapixels but we have four of them per camera
18:25which makes it 80 megapixels already per camera and if you put it to 26 cameras you have 2.1 giga
18:32pixels so 2.1 billion pixels really that we have uh at hand to do our observations so a slight improvement
18:41on my 12 megapixels i would say so so how important is the stability of the configuration yeah that's
18:50really one of the main drivers of the mission so we are looking at the southern hemisphere uh as our
18:56one of our observation fields and we want to look at this for two years within these two years what we
19:01are trying to achieve is that we have a variation of a target not more than plus minus one pixel
19:08over the cameras of the camera sensors the aim is to have the same star roughly on the same pixel
19:18for the full two years yeah that's in principle the idea that's astonishing yeah do you think plato
19:26will do it will it find earth 2.0 i definitely hope so and let's say statistics show that we have a chance
19:38it is thrilling to think that one day plato may detect other planets exactly like our own
19:46but while we wait to find out an unexpected gas giant is challenging our understanding of how planets
19:53form to y6894 is a faint red dwarf nothing to write home about and normally a star no one would pay
20:03attention to but a paper out last month revealed that this star has a planet all of its own and it's
20:10one that shouldn't exist i'm at the university of warwick meeting edward bryant who discovered this
20:20planet to find out more so ed what have you found so what i found is a new planet called ty6894b and
20:30what's really exciting about this planet is although the planet itself is just the size of saturn the star
20:35it orbits is only 20 the size of our sun i think i've worked out what these are for this football
20:41here shows the size of our sun in our own solar system with strange sunspots with some sunspots
20:46and solar activity going on and then the red snooker ball is showing the size of the star
20:51ty6894 relative to the sun and then the small bouncy ball there is showing the size of the planet
20:57both ty6894b and saturn saturn's the second largest planet in our solar system and though it's a gas
21:06giant it's less than a tenth the size of the sun's diameter
21:12ty6894b on the other hand is almost half the size of its red dwarf host star
21:18so is it unusual to have such a massive planet around such a small star it is unusual yes and
21:25the reason it's so unusual is because we wouldn't have expected that a star this small could have
21:30formed a planet this large why not so when we think these planets form protoplanetary disks
21:35these are huge disks of gas and rock and dust that surround the young star i've always thought of
21:40it as the leftover material from the star that's absolutely right it's everything that's left from
21:45the cloud that collapses to form the star and within these disks the solid materials of the
21:49rock and the dust collides together and over about a few million years or so builds up a very massive
21:55core that then will accrete gas and become the planet but the problem around these very low mass
22:00stars is we think that these less massive stars have less massive disks and so we wouldn't have
22:06thought that there would be enough material to form a planet this massive so what's happening is this
22:11some different form of planet formation or or is there something else going on so it could be a
22:17different form of planet formation or it could be that we just don't understand the disks very well
22:22so there's a lot of work going on currently to trying to understand these disks and these disks
22:27have not been studied in large numbers and these planets are very rare so this may just be the star
22:32that got lucky it could just be yes that this was a star that got lucky and for some reason had
22:36a disk that was a different composition than what we expected either more massive or a higher
22:42percentage of it was this rocky material that could form the core of the planet now what about the
22:47planet itself so we don't know much yet because all we have currently is a mass and a radius and an
22:52estimate of what the temperature might be like so how would we find out more about it by observing its
22:58atmosphere using transmission spectroscopy and using telescopes such as jwst so what will we learn from
23:06these jwst observations so as well as learning what gases are in the atmosphere one thing that we may
23:12be able to work out is the exact mass of the core and using that mass of the core that feeds back into
23:20what formation process may have caused this planet in the first place whether it has a very massive core
23:25or a less massive core that could have formed through a different mechanism
23:28more powerful cameras in space hope to reveal the secrets of planets orbiting distant stars
23:39it's by pointing a camera at the moon orbiting our earth that you can capture a rather special image
23:46pete is on hand to explain while short nights and not particularly dark skies can make stargazing
23:53difficult during the summer months the moon can always be relied on to delight and this is a good
23:59time to look out for an effect known as the moon illusion this is where the moon appears huge against the
24:09horizon and that is the key word because it is an optical illusion that only occurs when the moon is seen
24:17near the horizon and the reason why is currently a great time to look out for this illusion is that
24:24we're at a point in an 18.6 year cycle which means the fuller phases of the moon appear low to the
24:32horizon at this time of year you may have already seen july's full moon which barely scraped 10 degrees
24:40above the southern horizon that's less than the width of your clenched fist at arm's length the
24:47shallow angle of rising and setting for the fuller phase of the moon means it appears closer to the
24:53horizon for longer than usual and that's great for looking out for the moon illusion good nights to look
25:00for it in mid-july will be on the 14th or 15th of july and around 2340 bst when a waning gibbous moon
25:09will appear above the east southeast horizon then again on the 8th and 9th of august you can see
25:16the same effect with the full moon rising over the southeast horizon from around 2115 bst
25:24however photographing these moons can be disappointing and there have been many people
25:28who've seen a huge moon on the horizon taking a photograph of it with their phone looked at the
25:34result and being disappointed how small the moon looks but for amateur photographers it's
25:39all about the framing the key to getting a great picture simulating the effect is to ensure you
25:47have included something on the horizon to create the perspective your eye perceives to do this you
25:53ideally want to use a long focal length lens or a telescope and you want to frame the image to include
26:00some interesting but distant foreground object in the field of view get it right and the effect can be
26:07very impressive despite the long daytime periods there's plenty more to see at this time of year
26:16as always you can check out my more detailed star guide which is available
26:20at www.bbc.co.uk forward slash sky at night
26:30ever since i started out in research i have just fallen deeper and deeper in love with exoplanets
26:35because we're not just discovering these incredible strange new worlds we're also gaining
26:40a deeper understanding of how the universe works and i cannot wait to see what my guy plato and you know
26:47exoplaneteers in general just go on to discover surprising egg-shaped planets there are eyeball
26:54planets there are marshmallow planets candy floss planets
27:03but before we go there is one more thing this month marks 25 years since chrysalin top first
27:09appeared on the sky at night and in celebration of that is some of his best bits and now on to our
27:16main theme here we go ready for takeoff and with me mr slintos welcome to sky at night thank you
27:22tonight's program we want to talk about the saturnian moons an annular eclipse cosmic ghouls galactic
27:29cannibalism i can't wait it's going to be really exciting we're watching the team at mission control and
27:35they look pretty calm calmer than i feel anyway and that that was the annular eclipse where are you
27:43i'm at the institute of astronomy in the dome of my favorite telescope this is the cam in cambridge
27:49and we're just coming under the mathematical bridge i'm here on the icidis planitia i think you'd find
27:54mars a pretty pleasant place to be well it's flat and red one of the problems in exploring the solar
28:01system are the sheer distances involved maybe we just need to think bigger seriously this is too
28:06many chrises i don't think i expected that well there it is everyone cheering
28:14it's been absolutely incredible i think people are quite happy
28:19so i'm not sure what any of that means what do you reckon i don't understand it at all
28:24thanks very much and from the sky at night good night good night good night
28:54so
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