Good afternoon, ladies and gentlemen. Welcome to the 103rd Hall Lecture.
I'm delighted to be able to introduce to you today Professor Naveen Van de SEC from Leiden.
She is an astronomer and a chemist. And that's an unusual and very special set of skills.
She's a professor of molecular astrophysics at Leiden Observatory in the Netherlands and director of the Sackler Laboratory for Astrophysics.
She's also a member of the Max Planck Institute for Terrestrial Astrophysics in Garching.
She had her Ph.D. in Leiden before the United States for a while,
where she worked at Harvard Institute of Advanced Study in Princeton and Caltech before she returned to Leiden and became a professor there in 1995.
She works on interstellar molecules, star formation, planet formation,
submillimeter and millimetre astronomy and the basic radiative transfer processes that go along with working in that field.
She is an extraordinarily eminent astronomer.
She's a member of the Dutch Royal Dutch Academy of Sciences and the U.S. National Academy of Sciences.
She's played a crucial role in the development of many of the forefront facilities that astronomers use today,
most topically and recently the alma interferometer in Chile, the Herschel satellite.
And to be looked forward to the James Webb Space Telescope.
She was responsible for one of the instruments. She has published an astonishing 370 papers that have been cited over 20,000 times.
She's had 34 Ph.D. students. This is a remarkable person who's going to speak to us today.
There's a list of accolades which goes now down from halfway on this page to the entire other side of the page and beyond.
But I'm not going to read all those. I'll just pick a few. She's the gold medal holder of the Royal Dutch Chemical Society.
In 2000, she won the highest scientific wall award in the Netherlands,
the Spinoza Prize 2001, the Burke Award of the Royal Society of Chemistry here in the U.K.
She's a foreign member of the American Academy of Arts and Sciences, an honorary fellow of the Royal Astronomical Society,
and just last year became an Academy professor of the Royal Dutch Academy of Sciences.
So it's my great pleasure to introduce Professor Irene Van de Sic to deliver the 103rd Halley Lecture.
Building stars, planets and the ingredients for life between the stars.
If you. Okay.
Well, thank you very much, Roger, for this very kind introduction.
And I want to thank you and the entire department actually here at Oxford for inviting me to give this very prestigious lecture.
And so I'm really delighted to be here. Although it could be a little bit dry or on the other hand, my story is partly about water.
So maybe that's sort of good, a good omen.
And so what I'm going to do today is actually take you on a tour of the matter between to the stars,
the interstellar space, and see how how out of this very tenuous material that you see over here.
You actually built the stars and the planets and clouds like our own first that we that we live on.
So this is a very broad subject, and I'm going to tell it at a very general level as well,
because there may also be people from there, the general public here.
And but I'll interspersed with some more detailed recent results to give you a
flavour of everything that is happening actually at the moment in this field.
But before we do so, since this is the only lecture,
I want to make a tribute to Edmund Talley and all the work that he has done and is actually very relevant to the story that I'm going to tell,
because in the ends of my lecture, I'll get actually two comments and they're ingredients.
And so what you see here is, is basically one of the aspirations of Halley's Comet in 1986.
And of course, then we could take a first peek at the nucleus of a comet and actually see what it is made of and what it looks like.
And so the very end I'll come back to actually how these these nuclei of comets, these planetesimals are actually built.
But it's not just astronomers, that's physicists and scientists that are interested in this story of our origins.
It's you see it also throughout our culture in many different ways.
And one of my hobbies is actually astronomy and art.
And so I like to to find sort of pictures that have special paintings that sort of depict and also part of the story.
So, of course, in the Netherlands here there's several faces, Starry Night.
So you just have to paint this this picture.
If you go to German expressionists, Kandinsky already painted here the stars and even long before molecular clouds were known.
He already has these stars forming somewhere inside the dense clouds, and it's being heated and irradiated by some nearby star,
as you can see, as it's sort of a like if you go to another part of the world, here is Day Australia,
Aboriginal Art and with the seven sisters here sitting in the centre of the Milky Way, hidden there by their mother,
who keeps them away from Orion, which is the old man that is chasing actually these seven sisters.
And finally, you know, the Pacific Northwest and northern Canada.
And there is the story of a first raven actually stealing the sun out of a dark box where the moon to put it and then putting the sun up at the sky.
So these are all stories about stars, about the origins of stars, the origins of of planets that you see reflected actually throughout culture.
And in fact, of course, Halley's Comet has been an inspiration to many artists as well.
And the famous tapestry on bear here, where you see the Halley's Comet,
said a 1066 appearance, which was particularly bright and which you see up here.
And that also got a very famous painting in one of the chapels in Florence.
And where you see here, this is not the end of the negativity.
This is not the star of Bethlehem. This is actually a comet. And again, inspired by the 31 appearance of Italy.
But even the Native Americans reflect it and see it as actually in the petroglyphs.
Here again, to the 1066 appearance, which was so, so prominent.
And so basically the origin of of comets and the origins of solar systems is, of course,
a topic that has now become very much in the forefront again with the discovery of exoplanets,
planets that circle around stars other than our own sun.
And it's only less than 20 years ago that the first exoplanets were discovered by now.
It's a field that is really booming. It's one of the fastest growing fields in astronomy.
And right now, close to a thousand exoplanets have been discovered.
And that makes all of these questions as to how these planets were actually formed,
whether these outer planetary systems are similar to our own or not.
How unique is our own solar system also in its architecture, and which of these planets could actually be habitable?
And so that is sort of the context of the story that I would going to tell you here today.
So let's orient ourselves as to where we are going to look for America to look very much in the solar neighbourhood, close,
close to home, so to say, because that's where we have the highest spatial resolution, that's where we can see the sharpest.
But all of the processes I'm going to tell you about actually happens throughout
our entire Milky Way and even in other galaxies out to the edge of the universe.
In fact, molecules like water and carbon monoxide have now been seen out to distances corresponding
to when the lifetime of the universe was only sort of 10% of its current age.
So really very, very large distances. So so this is basically to remind you where we are actually where here,
if you would look on top of our own Milky Way and our Star of the Sun is only one of some hundred,
several hundred billion stars here in this Milky Way, and then sort of halfway out to the edge of the Milky Way.
So why are these stars and planets formed? Well, they are formed in the very tenuous material that is between the stars.
It was only sort of around 1900s that astronomers realised that the regions between the stars were not empty.
But the field is a very, very dilute gas and it's the more denser concentrations of this gas where the stars are being born.
So here's a good example of one nebula where we actually have a lot of stars being formed at this moment here in the famous constellation Orion.
And here we have done the Orion Nebula. And if you look at it with a more modern telescope, then you see that it's not just a few stars,
a few bright stars that were seen already by 300 years ago.
But you see here, actually, a nursery of some hundreds young several hundred young stars.
Now, William Herschel, he actually speculated already that something like the Orion Nebula,
which he was able to see this little telescope in his backyard, that these were the chaotic material of future suns.
But at that time, when Herschel said this, it was not even realised recognised that stars actually don't have very internal life.
Stars actually are born and they also die again.
And and and that's that is an integral part of the whole story.
So the Orion Nebula is actually one of the prime nurseries of new stars in in our galaxy.
Here you see another image in this case taken by the Hubble Space Telescope, now on a somewhat larger scale.
And you see also these dark regions here. You see them also in other places, these these bright nebulae, a sort of dusty,
ionised gas that is emitting brightly in the the optical wavelengths regime.
But you see also here, these these very dark clouds. And these clouds are dark because they can contain very tiny dust particles,
small silicate material, small carbonaceous material, which absorbs and scatters starlight.
And that is why these clouds look so look so dark.
And we can see them them as a silhouette, basically against this bright background.
Now these clouds are large. They can be several light years across.
They can also be very massive. Some of these clouds or the larger cloud complexes can have masses up to a hundred thousand solar masses,
meaning that they have enough material in order to 400,000 new suns.
They won't do that. They actually have a lot of low efficiency of forming new stars.
But in plants, in principle, there's lots of material presence to do so.
So let's look in a little bit more detail at some of these dark clouds.
So here you see a nice example. I show that there's a small dark cloud also called a coal sack.
This one actually on the southern sky. And you see it again hanging here in front of the thousands of stars here in the Milky Way.
And so these clouds contain about 99% gas, mostly hydrogen, and about 1% by mass of this solid material.
And as I mentioned already, this sort of material is typically silica silicates.
And I've seen gas, little sounds, grains and also carbonaceous material.
And it's typically only a 10th of a micrometre in size and thousands of a ten thousands of a millimetre.
So very small dust particles. And but they are responsible for making these clouds look dark.
And thus we will see.
They actually also play a role in shielding the molecules from the dissociated radiation of the stars and therefore making them survive.
These clouds are cold, stay only slightly above the absolute zero,
and they have densities of typically about a thousand particles per cubic centimetre.
Now this one cubic centimetre here in this room contains probably of the order of ten to the 19 particles per cubic centimetres.
And even a good vacuum in a laboratory on Earth still, still has something of the order of, say, 100 million particles per cubic centimetre.
So what an astronomer calls a dense cloud is still a much better vacuum than we normally have in the laboratory on Earth.
And that is really what makes these clouds also so interesting for chemists, because they are actually quite unique.
Chemical physics laboratory. So how do we observe these clouds?
Well, it's nice to see these dark regions here in optical image, and that certainly recognises that.
You recognise that there is a cloud there. And but if you want to see actually what's inside the clouds, then we need to go to longer wavelengths.
You basically need to put on the glasses, we need to put on infrared glasses or even longer in order to go to the longer
wavelengths where the scattering and absorption of the light is much less.
And so you see here an image of the same cloud, but now in infrared wavelengths.
And you see that you can actually see through the clouds and see the background stars.
But you can also now actually studied material that is present inside of clouds.
So this is actually a nice movie that was made by the Spitzer Space Telescope, a satellite which flew between 2003 and 2009.
And what we are doing here is we're taking here one of these dark clouds.
And so these are actual thermal images, actually, from one of our programs.
And it's we go as we are zooming in, we're also going to do longer and longer wavelengths.
And so we're zooming in. And what we see is that the dark regions disappear.
And actually inside this dark cloud there is a young started is at this moment being formed.
And these young star is still trying to push away the surrounding material through the so-called
jets and winds and jets that it has here in these two directions in a bipolar direction.
So the colour coded here in this image is such that says here is obviously to start and that's
the green is a filter that actually contains the hottest molecular gas and the rarest.
A red filter that you see here is actually a filter that contains emission from very large molecules d so called polycyclic aromatic hydrocarbons.
And so these are actually molecules that are being excited by this radiation that emits them in the infrared wavelengths range.
And that's see that's what you see here, nicely reflected in this in this image.
So astronomy is very much driven by the facilities, by the big telescopes that come that allow us to to observe at various wavelengths.
And we have been very fortunate that in the last decades to have a number of very powerful telescopes that are very well suited,
especially to to probe into these dark regions.
So here are my examples of the space telescope.
And I want to mention in particular the Herschel Space Observatory, which is actually the largest astronomical telescope in space.
In fact, it's run out of coolant just a few weeks ago.
So it was launched in 2009 and it was operative until just a few weeks ago.
But at this very moment, we are still very busy and analysing all of the results from this from this telescope,
especially for one of two instruments, two hi fi instruments that was actually built under the leadership of of the Netherlands.
And of course, we want to go above the Earth's atmosphere,
because the Earth's atmosphere actually blocks a lot of the radiation and prevents it from coming to Earth.
And especially because our radiation, our atmosphere contains so much water and oxygen and also CO2,
we really have to get above the Earth's atmosphere in order to observe these crucial ingredients and for chemistry.
Just to give you an indication of the progress that we actually have made.
So 30 years ago,
this was sort of the best image that we could take in the far infrared wavelengths range C around 100 micrometers off such a star forming a cloud.
It was really not much more than a sort of a single pixel on the sky.
And so if you look basically at the kind of images that Herschel has been returning,
and then it's really fantastic to see the detail now in all of these molecular clouds.
Again, the colour coding is such here. That's really was actually two shorter wavelengths and red is the longer wavelengths.
So here we're looking at the somewhat warmer parts of the sky.
This cloud is irradiated by a bright star from this size.
And here we're looking at the somewhat cooler part of the cloud.
But all these little point sources that you see over here are actually new stars that are being formed at this very moment.
And we see already filaments and ridges, etc., which is where most of these star formation takes place.
But it's really beautiful to see how Herschel has sort of unveiled these these clouds.
And as we can now look at them in the thermal emission, basically, that is so-called dust grains emits.
If you go to a somewhat later stage, if you look at where planets are being formed, again, we have come a long way.
This is a famous graph from the iris satellites, one of the first infrared satellites which saw an excess of emission over a stellar photosphere.
And now as Herschel, actually we have been able to make an image.
So what used to be just one flux at a pixel is now a beautiful image here of this as the source,
where here we have two star and here we have a ring of cold dust where there's just this small dust grains actually produced by collisions of big,
bigger blocks and that are actually the remnants of planet formation.
And I will come back actually to this this kind of process at the end of my talk.
And of course, the private savvy also have very powerful telescopes we can think of to the very large telescopes of the European Southern Observatory,
which are the possibly the most powerful instruments that we have on Earth.
And if you go to longer wavelengths than we have some of the pioneering millimetre telescopes.
And I want to mention here, especially the James Clerk Maxwell telescope,
which has been a and still is a collaboration of and does in the United Kingdom.
So England and the Netherlands and Canada, although the Netherlands just ended its participation,
but for many years we have been observing together actually here on this telescope and basically opening up the millimetre wavelength regime.
And of course, the major new facility that has just been inaugurated only two months ago here in Chile is the Atacama Large millimetre array.
Oh, wow. Here is a picture that's actually representative of the day.
This is a big collaboration, actually, of the actually the first worldwide collaboration in astronomy,
both Europe and North America and also East Asia, coming together to build 66 telescopes on this high site here in Chile.
And I'm very pleased to see actually that's Richard Hills,
who has played a very important role in making this telescope actually work, that he's actually here in the audience.
And we owe a lot to him and all of his other staff of the observatory to provide us with some of the beautiful images that we are now getting here.
And this is what it will look like in about a year time when all of the 66 telescopes are there.
And I can assure you, it is really already a breathtaking experience to be there, both literally and figuratively.
And they're up there at 5000 metres. And I always open up, up as scientific eyes.
Just to give you an impression of what the facility looks like.
So here is basically at the 3000 metre level is where the telescopes are being assembled and then they are put on a big truck
and then driven up to the road here to the 5000 metres region where they're built and then used for scientific observations.
Okay. So that is some of the broke ground down on the facilities that we're using.
But the observations are only one part of the story.
If you want to learn something about stars and planets and especially the ingredients that go in there,
and then you have to also combine it with models and also what I call the laboratory,
although that can also be a computer actually laboratory, which provides the critical ingredients for both the observations and the models.
So let's talk a little bit about the ingredients that we actually have in these clouds.
So this is actually the astronomers view of the periodic table, which emphasises that the universe is mostly of hydrogen and followed by helium.
But helium is chemically not that interesting, and that's a chemically interesting.
Elements like carbon, hydrogen and oxygen are really way down at the level of a few times 10 to -4.
Ms. Respect to hydrogen. And so what we have is this very tenuous gas.
Very cold, mostly hydrogen here and there.
And interesting elements. These elements may not meet each other, you know, for 25 years or so.
So chemists had always told astronomers, well, don't bother to even go out and look for molecules because you simply won't see them.
Well, fortunately, the astronomers didn't listen and they turned to the receivers and actually found a whole wealth of different molecules there.
So this is just an example of the richness of features in the Orion Nebula.
So now we are taking Herschel and pointing to Hi-Fi Instruments, a natural light instrument on the Orion Nebula.
And this is an almost complete spectral scan.
And it's you see already there are lots of lines there, but it's just to warn you that this is not noise.
But if you start to blow this up, then we actually see that this little part is actually there are all all real
lines and there's no no noise whatsoever that you can see in the spectrum.
You see already here patterns of certain molecules. And you can try to assign these all of these lines.
And if you have enough left catalogues of lines and you find that we find see both simple and also rather complex molecules present in these clouds.
So this whole feature, this whole pattern of lines is all due to one molecule, methanol.
But you also see simple molecules like sulphur dioxide.
Several lines over here and more complex molecules like that.
Methyl aether or metal formate. You also can get some kinematic information from the lines here.
You see how beautifully resolved this line profiles are. This is a case of water.
And you see already that this water is is moving actually very fast, up to 100 kilometres per second.
So we also get some information on the the kinematics.
So just to summarise, that's the kind of information that we can actually get here from these these lines.
We get information on the kinematics,
we get from the line intensities we can and count basically how many molecules there are and translate that into relative abundances.
And then from the line ratios, they tell us something how often a molecule colitis and not a molecule in order to get its excitation.
And that tells us something about physical conditions like temperatures and densities in this class.
So these kinds of data, these kind of spectra actually contain a whole wealth of information.
This which you can characterise the class.
Just to show you some of the molecules that have been detected, some of the complex, more complex organic molecules.
And here is already that methyl aether that I mentioned.
So one of the simple sugars that's I'll be talking about a little later as well,
that glycol aldehydes that is seen ethanol is seen in quite a substantial abundances actually in these clouds.
And molecules like benzene have also been detected. But if you think of molecules that we would need to to say this is prebiotic material
that we would need to to make a DNA and RNA of potential life elsewhere in space,
I can think of simple amino acids like lysine or bases like Purine and Pyrimidine, and these have all not yet been detected in space.
There have been many claims and there was it the the refereed literature in the press that this molecule has been detected.
But so far that has not yet been formally seen. But this is exactly what's what Alma will do, because it will have such high sensitivity.
It will actually be short being able to show how far it is, chemical complexity and actually go.
And this little molecule here, caffeine, although not necessarily for the origin of life, is certainly necessary for the maintenance of life.
So and that's the molecule that we also still have not yet discovered in space,
that it's actually not much more complex than some of the molecules that have been seen.
So who knows what we will find? And even larger molecules are presence in space.
I mentioned already this polycyclic aromatic hydrocarbons which have a very characteristic infrared emission.
In this case, we don't know exactly the precise molecule that we have, whether it has 50 carbon atoms of 40 or 60, and how many hydrogen star.
But we know as a class that these molecules are certainly present.
A very recently actually also the first Fullerene C 60 and 70 were actually discovered in space.
Of course, Harry Kroto was originally a master chemist and he got much of his inspiration for his work on C60 from working on these interstellar
molecules and and wondering if you have these long carbon chains and you start to wind them up and basically what kind of molecules he gets.
And that's one of the the roads that led him to the discovery of C60.
So far I've been talking mostly as molecules, as a gas, but actually because these grains are so cold today,
they sort of act as a deep freeze and on which molecules from the gas can basically collide and stick,
much like you can get icy your freezer or in the cold winter nights,
you get molecules from the atmosphere that freeze out on your windshield and form a little icy layer.
Now, once the molecules and the atoms are on the grains, then other chemical reactions can occur,
especially as reactions with hydrogen become much more prominent.
So you can turn actually oxygen into water and you can turn carbon into methane,
and you could turn nitrogen into ammonia and carbon monoxide, which is another main ingredient of this cloud.
You can actually hydrogenase it all the way to methanol.
And that's actually one of the reasons why medicine all is so prominence, why methanol plays a very important role in that and interstellar chemistry.
So actually enlightened in the sexual laboratory by trying to simulate these processes.
And of course, we can never simulate all the conditions we need to speed it up.
We cannot wait for four times of the five years for our reactions to occur.
And that's certainly the temperature we can that a beacon and also basically make sure that we
only look at and say to body processes that we can actually extrapolate to much longer timescales.
And so the laboratory is now actually under the direction of Hydrothermal March and we are doing still continue
to collaborate on a number of processes that are directly relevant for what is happening in interstellar space.
So that's an example of we actually tell you the story about water, because water is,
of course, one of the main ingredients for for life on other planets.
And thanks to the Herschel Space Telescope,
we've now been able to obtain quite unique data on what it can tell us and give us insights into questions such as
how and where water is formed and how it is actually transported from a collapsing cloud onto a forming planet.
So just to show you that this is not just interesting for astronomers, you see quite a lot in the popular literature.
And this is challenges for life on Mars. And it says just at water.
And here is actually what they think, that the NASA's spacecraft, when it finally gets to a new planets, they will actually see in terms of water.
So it simply shows the importance of water in all of the story.
So the program that we have been carrying out over the last several years is dead
in the water in star forming regions with Hershel program abbreviated as wish.
And she says it's one of these large collaborations that we now have in astronomy where you actually get a
quite a number of hours in this case of guaranteed observing time as a return for building the instruments.
And then we have less clear collaboration between some 70 scientists from 30 institutions.
And that's done carry out this joint program.
And so we're now in the States that we have all the data, but we are still digesting sort of all of the results that I think that we now
have a much better view as to how we think actually that water is is formed.
And really, look, not most of it actually happens on these dust particles.
So what you see here is a global dust grain where maybe once a day you see a the hydrogen atom actually lands on this grain.
You also see the oxygen atoms, the hydrogen atoms find each other and take off as a hydrogen molecule.
But you can also form a water molecule there. And here you see already another two molecule actually being formed.
And now they're making the hydrogen peroxide radical. If you make hydrogen peroxide.
Yes. Here. And we actually form a water molecule.
And these were all processes. That's where we zoom forward in time,
fast forwards and that's then how we make our our ice layer actually on the brain and then end up actually with an is an icy grain.
So a lot of these processes are actually pushing AIDS.
It's already 30 years ago, but we simply didn't have the laboratory experiments in order to test these these hypotheses.
And it's really, I think, a success story of the interaction between astronomy and laboratory astrophysics that we've now been able to to to verify
all of these processes in the lab and actually show also how they occur and measured are rate the rate constants.
So we can then try to to quantify this down and look, for example, at here, what is this dark cloud and why we know that we have mostly ice in there.
And then we can say, well,
the water that we can actually see in the gas is basically a balance between the formation of water on this ice that I just showed you,
and then getting the molecules back of the grains again back into the back, into the gas phase.
And that should then give us our signal in terms of of water that we get from this from this cloud.
And that's indeed what we have observed as part of the wish program.
We have now detected for the first time basically that the Colt gaseous water reservoir is Herschel.
And one of these clouds, probably a cloud of is on the verge of forming of collapsing and forming a new solar system.
And the signal that we see here is very much in agreement with sort of this theory of water formation and desorption that I just sketched to you.
So it looks like we have learned a lot about the water formation in space.
It's also clear that the bulk of the water is already formed during this early stage.
So the water molecules that you see here in this glass and it's may well be the water
molecules that were formed some four and a half billion years ago in the cloud,
out of which our own solar system formed. So that's an interesting thought to keep to conclusion.
And we also see the water associated with the forming Protostars.
Here is still some beautiful example of the quality of the data that we're getting,
and it tells us that some of the water is not only in falling, but some of the water is also outflowing.
There's very high velocities at 200 kilometres per second.
And in fact, we see the water associated with these jets that we that are associated with old forming stars.
And we can now even make maps of of water associated with forming stars.
So here is the protostar basically. And there you see the outflows to bipolar outflows which are lighting up in water.
So basically what you're seeing here is maybe a young version of what our own solar system also looked like at some early stage.
Very it had basically these these water fountains on both sides.
So this is basically where the water is, is lighting up.
So to summarise so far interest, our clients clearly have a very rich chemical composition in spite of the very cold and tenuous conditions and
complex molecules and water are basically found around nearly all the forming stars and throughout the Milky Way.
And this means that at least the ingredients,
the building blocks for prebiotic material are widespread throughout our Milky Way and presumably also through other galaxies.
All right, so let's now form a star out of these clouds. And I'm going to look a little bit more at the physics and effects just collapsing.
And then forming a star is not so simple. There's a lot of physics that is actually associated with it, which I won't go into during this lecture.
I just want to show it to you here in a movie that is actually based on real data from the Hubble Space Telescope
taken by Chris O'Dell and then turned into a movie and basically taken the data making from the two dimensional image,
three dimensional image through which you can then zoom in and in a computer.
And here we now go to an animation where you actually see this envelope around the collapsing star.
And here you see to the young star itself was a rotating disk of gas and dust and is this disk in which the planets can subsequently form.
So let's look at this once more. Here we have our two dimensional image again of Orion.
We're going to now fly through it.
And so what you see is already several of these protostars of collapsing clouds in which a new star is already being born.
They're still embedded in their envelopes.
And these envelopes are basically blown away by these by these jets and also by the radiation from the young stars in the surroundings.
And here we now go to the animation. The envelope is basically being dispersed.
And what we see now is still the young star,
but it's surrounded by this this rotating disk of gas and dust and in which the subsequent planets can form.
And such a rotating disk is a very natural outcome of a collapsing cloud that has initially a little bit of rotation to go with.
So here you see the still image from Hubble on which the movie was based.
And you see already that you have to look really was a magnifying glass in order to see these young stars, Mr. Disks, surrounding them.
And then we can see them here as silhouettes against a bright background.
But these images, which are here by now, almost two decades old, were still very important to show the sizes of these disks.
And because you can now put our own solar system at a distance of Orion and you can show that is very much the same size.
So showing that these disk actually have sizes that are equivalent,
so to say the distance from centre of Pluto, which is some some 40 astronomical units.
So what we now know is that nearly all the young stars in the in their surroundings are have
these disks and that the sizes of the disks are comparable to the sizes of our own solar system,
and also that the masses of these disks are usually enough to form a solar system.
And that is about 1% of the mass of the sun, or about ten times the mass of Jupiter.
If you think about how much mass you needed to make our own solar system,
that's about ten times the mass of of Jupiter, because some gas has been lost from the solar system during formation.
So this means also that our ingredients actually for planet formation are gone.
That is also something that we're finding throughout.
Okay. So but what is the problem? Well, here we go back to our Carina Nebula.
And here we see these clouds and these we can easily resolve this current instrumentation.
And even the collapsing forest is collapsing regions. We can also still resolve this current instrumentation.
But if I take a here a disk and this is an artist's impression of a disk, then I wish it was as big as this on this scale.
But it is not. It's much smaller.
So basically if you would look at what the disk would be, it would really be sort of tiny, tiny, tiny on this on this scale.
And so this is really why we need an instrument like Alma to basically zoom in on these
regions and to have the sharpness in order to to study these to study these disks.
So let's look a little bit about what we now know about these about these tests.
First, let's talk a little bit again about our water story, because water plays an important role in planet formation.
We know that in our solar system and also in other solar systems, there is the so-called snow line, which Stewart says already.
It's the line beyond which water actually exists as an ice.
Or you can also call it Iceland. And that is sort of close to where Jupiter is, a little bit more inward.
Currently, within the early solar system, it was somewhere around where Jupiter now is.
And if you actually freeze out water and then you enhance the density of the solids and
that makes actually that's your whole planet formation process is actually more rapid.
And they are trying to basically get from these small dust particles to a larger and larger dust particles, the inner parts inside the ice line.
That's where water is mostly as a gas, and that's also where the water gets very hot.
And that is water that we can actually observe is other telescopes and more infrared telescopes in this area, the Herschel and the Alma telescopes.
And so what we've actually been trying to do is we have been trying to use Herschel in order to detect a water gas,
because that is actually providing us with a direct measure of how much Easter
is as through the same sort of processes that I illustrated you earlier for.
It is collapsing. Cloud and ice itself is very difficult to detect in these climate.
And so this is one of the highlights of our wish program,
also the detection of cold water in these disks and shown here from work from if you look ahead as well.
And the signal actually, we can translate into a number of water molecules are there.
And since Science magazine likes it, mostly the units of oceans.
We translate this into oceans of water, which is about 6000 oceans.
And but you can, of course, translated also into grams or whatever.
And I can give you the conversion factor for that.
But it shows already that this disk contains certainly enough water to fill several oceans on a on a new planet.
The other thing that we've done is we've used actually, Oliver. These are data that were released by the project as science verification.
Basically, the project was trying to see whether Alma was working well.
And we had some old data showing these three lines here. And so they took these data and they said, oh, we see these three lines.
That's great. Alma is working fine. And that's even in its early stage.
When this was still done, there's only 16 antennas.
Alma was already so sensitive that it's not just these three lines, but it saw a whole bunch of other lines already appearing here in these data.
And together with zero consent from the University of Copenhagen,
we dug into these data and we discovered quickly that several of these lines were due to interesting molecules,
actually quite complex organic molecules. What we're looking at here is a forming protostar, a very low mass protostar and not seeing as big as Orion.
But just a tiny little start is forming at the moment.
And this tiny little star already has very complex molecules associated with it and even quite complex ones like this.
There's little sugar here, like, well, aldehydes and we're over.
Oh, my God. Already see? So sharp and that we could locate the presence of these molecules to within 25 astronomical units from the source.
So now we're no longer looking at large scales? No. Now we're looking really on scales of these disks.
Well, basically corresponding to the orbit of Uranus.
And we are finding already these complex molecules there. So what we're seeing is that they're both with Herschel, but now particularly with Alma,
we are able to really zoom in and to these disks in which planets are forming and that we can actually characterise these and their composition.
Okay. Back to a little bit of arch. What you see here is actually a English engraving from 1798,
which is actually hanging in our living room and reminding us that's already decked as what is it?
Centuries ago, artists were speculating that our solar system is just one of many,
and that is our solar systems don't need to look at all like our own solar system.
Some of them have less planet, some of them have more planets, some of them are close by and some of them are further away.
And this is exactly what is now being revealed by these detections of exoplanets, that there is a huge diversity in planetary systems.
And so that's, for example, at the Kepler satellite and is is finding a huge diversity in in planets.
So. But where does this come from? Well, the answer lies clearly in the past, during the time that these were assembled on this planet.
And that happened really in the disks and these rotating these through Hunter young stars, which contain a material out of which they they formed.
So in a very simplistic way, what is happening is that this gas and dust,
you know, that came from this collapsing cloud and that's entered into this desk.
So of which we now know the ingredients that basically these small dust particles started to coagulate and grow and grow into larger particles.
This is not as simple as it looks here in this cartoon.
And in fact, in my seminar tomorrow in the astronomy department, I will tell a lot more about these digital processes.
And what we are learning about is at the moment as to how these various particles can of coagulate.
But it's clearly happening and some of that we can actually see in action.
And these are some first results from the AMA, again, on these discs in which we think that actually planet formation is occurring at this moment.
So this is an artist's impression where we see one of these dusty disks,
but then some of these holes here, which are two locations in which if I go back here,
an image of planets may have formed already,
and which is basically clearing out its past by attracting the gas and the dust and thereby creating this gap here in these disks.
We cannot see the young planet itself, but we can certainly see the result of what it has done that they re creating this this gap over here.
And we are now starting to see this precedent of sharpness, actually, and these these gaps and holes in these disks.
And there are some surprises associated with that. So that I will tell you more about again tomorrow.
Okay. In the last few minutes, let me make the connection done with our own early solar system.
And let's go back to comments. Let's go back to comments like comets, Halley.
Halley's Comet or Comet Hale-Bopp. A beautiful example, a very bright comets in 2005, a new comet that is coming back of a ten stars.
That's Will and maybe somewhat later in the year will be actually visible.
And the good thing is that we now have these powerful telescopes that we can
actually point at these comets and that we can then study their composition.
So what are comets? Comets are basically these coagulated and icy dust grains and grown to something like a kilometre in size or a few kilometres
in size and which have most of their time spent in the outer parts of our solar system where it was very cold and radical,
basically be preserved. So we think that comets actually contain the most original primitive material that we have in our solar system.
And so they tell us also something about the past. They tell us the story basically also of the formation of our own solar system.
And so we can now point our powerful telescopes at this comets and study their chemical material that they have.
And what we find actually is that the chemical composition is actually very comparable to what we see is these
interstellar ices suggesting that these are indeed sort of a leftover of the formation process of our own solar system.
So that basically they're the building blocks that didn't make it into comets are scattered down into the outer solar system.
We can actually make time to make some connections and also what we see on Earth.
There is one big question there, namely whether comets actually did bring the water on earth.
Where does the water on earth actually come from? And again, thanks to high five,
we have another part of this story because high fire Herschel could observe not just water but also refrigerated version,
a video where one hydrogen is replaced by a heavier version of hydrogen deuterium.
And it's actually this ratio which would then go compare with the ratio that we have of water in the oceans glass.
And that is thought to be a diagnostics of what's the. What did the original materials that brought us water on the earth?
And what Herschel actually found is at least two comets in which this ratio is within 20%, exactly the same as we have in water in our own oceans.
Previously, there have been measurements that suggested at least two factor of two discrepancies,
but that factor of two has gone away with these new measurements suggesting that Reza's least one
family of comets that has the right isotopic composition and could have delivered the what on earth?
Now you may already think of delivering water on earth. How does that how does that work?
And because if you have an impact, then a lot of things can, of course, happen.
And in fact, if you have a massive impact of a very big object and maybe a mars sized object that impacted our own early Earth,
then it's clear that not much of the water and organic material that is present in these comments that as would actually survive.
We think that actually an impact phenomenon like this was responsible for the formation of of our own moon.
And so you don't need to do this. You should not do it this way, because then there's not that much is left.
And so you do try to do it a little bit more gently.
So not larger comets and and maybe sort of having the comet disintegrating and
bring it in in smaller pieces on Earth so that it's so dense can still survive.
But this is obviously also still one of the big questions as to how you make this this work and.
Exactly. Finally, if you want to link down with exoplanets.
And then the next step in this research is basically to look for the chemical ingredients,
not just of the star forming regions or the planet forming regions in which the stars and planets are being made.
But to actually look at mature planets and look there at their chemical compositions.
And so this is deep echo for the next generation of optical infrared telescope,
such as the extremely large telescope that has to actually have power to take
spectra of these of these exoplanets and determine the chemical composition.
I think one of the main messages of my story after this lecture, actually,
is that a lot of this chemical composition can and is already determined at the time of their formation,
only at a location in the disk where they being formed, whether they were formed inside a snow line or outside the snow line.
And the same actually for the carbon rich material.
So we found the entries, this summary. We started off as clouds.
We saw that they have actually a very rich chemical composition.
You see that out of these clouds and they can collapse to form a young star in that these young stars are surrounded by disks.
We are now starting to determine the chemical composition of this material here in this disks.
We know that's out of these disks through the coagulation of the grains.
You can actually form planets. And much of the same material that we had here is actually transported to these disks,
is also transported to the icy bodies in these new solar systems, such as you see over here.
And some of that material can indeed and also have been brought onto these new planets.
Of course it's to her. Also, our son doesn't have eternal life, so at some stage they will run out of nuclear fuel and they will die of that.
They will swell and they will come much, much bigger. They will swallow basically much of our solar system.
They will also then return some of the heavy elements that they made in their nucleus through nuclear burning and like carbon, oxygen and hydrogen.
And they bring that back to the interstellar medium and then a whole new cycle of star formation,
climate formation, and then stellar deaths, planetary deaths, and start again.
And of course, in our own Milky Way, the cycle has occurred already several times.
So to sum up then chemical ingredients and our present storage space and they are associated
with this way all the forming stars transfer systems are possible under majority of stars,
whether they actually form. And it's still a bit of a question,
although the exoplanet statistics seem to indicate that at least one planets per star is certainly
the possibility and formation process is now being actually unravelled based in new telescopes,
the new instrumentation, they're basically driving to science.
Herschel Alma And our next goal is really to image the physics and chemistry on these solar system scales.
So I'll leave you with the thought of bringing art and science and astronomy again together.
And the Australian Aboriginals already had a milky Way dreaming and comets featured already in some of the dreams that you see of the artists.
As astronomers, we have dreamt for more than 30 years we've dreamt of Herschel,
we've jumped of Alma and now these facilities are with us and are doing fantastic science visit.
Thank you very much.