As you know, today we'll have a public lecture by Professor Adam Leroy from the Ohio State University.
I would like to say a few words about the lecture. So, of course, in the physics department, we have a number of regular public lectures.
This isn't one of them. So the star visiting lectureship is actually a program from the university that aims to bring
American professors to the university to interact with people here to participate in the life.
In this case, that involves Adam participating in a workshop while the college on giant molecular clouds.
And if you don't know what this is yet, I'm sure you'll know within the next hour.
Then we'll also meet our graduate students tomorrow. And the visiting lectureship also involves Adam giving this lecture.
So you're most welcome.
So Adam is a product of the University of Berkeley where he got this position focus, former supervisors saying that here on the front the ability.
So it's a kind of a family affair.
He went down to the Max Planck Institute of Astronomy in Heidelberg, where we have also a number of people here for the workshop.
He done sorry was then a Hubble fellow, which is a very prestigious fellowship funded in the US through Naza,
obviously related to the Hubble Space Telescope. So he was based at the National Radio Astronomy Observatory for a few years,
then became a staff member there before moving to the High State University where he is now in Columbus.
And so Adam, along with a number of people in the room, have been here for the whole week to discuss essentially what we call stellar nurseries,
the regions where new stars are being born there, regions which by astronomy standards are very dense.
Of course, by a common earth, standards would be essentially probably nearly perfect vacuum,
I suspect actually better action than we can achieve in our lives.
But by astronomy standards, there are very, very dense regions and there obviously where new stars are born.
So Adam has made a speciality throughout his career to study these regions in both in the Milky Way and in external galaxies primarily.
And so that involves studying essentially what we call the different phases of the interstellar medium.
And as the name suggests, this is essentially the stuff between stars.
So it's a kind of tenuous gaseous material that could be dense and in molecular form,
less dense in atomic form, or perhaps also ionised when it's up to higher energies.
And I'm sure Adam will, you know, illustrate this with a lot of pretty pictures.
Of course, that's something astronomy is good for. But for the moment, Adam, thank you very much for the lecture and the course.
But yeah, exactly. So thanks very much to Martin and to the invitation to speak.
And exactly as Martin said, what I'm going to tell you about today is one of the most exciting current areas in astronomy that may get a
little bit less airtime than some of the results from the Hubble Space Telescope and some of the space missions.
And this area is the area of microwave astronomy or millimetre and submillimeter astronomy.
And the reason this is so exciting is exactly as Martin says, this is a field where we've just turned on essentially the biggest,
most complicated telescope on the ground that we have ever built.
And this is the Atacama Large Millimetre Submillimeter Array,
which is essentially an amazing machine to watch stars, planets and galaxies be born and grow.
And so this is this thing turned on a few years ago and has essentially been revolutionising
every field that it's actually able to make contributions to in the intervening time ever since.
And it's really just getting started. So if you take nothing away from this talk except the fact that you should keep your eyes peeled and your vocal,
your favourite news site or your local newspaper for the cool stuff that is coming out of Alma over the next year and over the next decade.
So just by a by way of a little bit of background, when we look up and see the universe around us with our eyes,
of course, what we see is a universe of stars that we see with our eyes,
a few thousand of them, and a universe of galaxies just really epitomised by this picture on the right,
which is maybe the most famous picture that Hubble has ever taken.
And it's a wonderful picture because it really consists of pointing Hubble at the blank s part of sky that you can find,
and just seeing the galaxies fill the universe heading out in every direction.
But we know that these stars and fundamentally what we're seeing here is starlight have not been around for the entire history of the universe.
The universe filled mostly full of just hydrogen and helium gas.
And some 13.8 billion years ago, there were no stars and there were no galaxies.
And when we take pictures of the universe shortly after this time, we see a universe full of gas and dark matter.
But not these things. So there is a huge branch of the field of astronomy which is concerned with the question of, you know,
how do we build the structures that we actually look around and see the stars, the galaxies?
And increasingly, over the last decade or so,
the planets that we know populate the orbit of the stars around us in the Milky Way and must also fill the universe.
So the broad picture that we have, you know, we have reasonably understood, which essentially amounts to gravity winds or to some approximation,
we know that the universe formed in the big bang form of hydrogen and helium.
There were some initial concentrations where matter was denser and the gas that formed in the early universe flowed on to these denser peaks,
and that flows on to these denser peaks. These things become galaxies.
Material continues to flow in over the course of cosmic time, and the material that flows into these galaxies forms,
stars, forms, the spinning disks of galaxies, and the material that has not yet formed into stars,
as Martin said,
lives between stars in a medium of hydrogen and helium and other gases that I'll mention that serve as the fuel for the next generation of stars.
So of particular interest inside these galaxies, as gas flows in, are these very dense pockets of gas.
So these represent the point at which gravity has won enough to collect hydrogen
and helium into clouds that are comparatively very cold and very dense,
where we we think that essentially all stars and planets form.
So these stellar nurseries, which all come back to quite a few times during the talk,
are really the places where we think that galaxies and stars are forged.
And it turns out that Alma is a completely revolutionary machine for looking at these stellar nurseries.
So I'm going to unpack this in various ways through the course of this talk.
But the part the thing that I want you to take away from this very general beginning is that
when we look up every star in every galaxy that we see ultimately formed in one of these cold,
dense, stellar nurseries out of the gas between stars and this process is still ongoing today.
We only need to look at the easiest constellation to find in the sky, Orion,
in order to see the process of young, new stars being born out of a cold, extensive cloud.
And I'll show you a picture of Orion in just a second.
But so in general, our a huge chunk of our field is deeply concerned with this question of in detail,
how do we actually form this material that started off as just diffuse hydrogen and helium gas into stars, planets, galaxies?
What determines why you have a star here or this set of planets around this star, and what drives the formation of the first galaxies?
And so this is hard or even impossible to do only with the light that you see from your eyes.
And to see this, I really like sticking with Orion for just a second and showing how Orion looks to someone using optical light on the left,
you may you see the familiar constellation that you can pick out with your eyes.
And this includes the some of the young stars that are forming nearest to the sun.
And on the right. What you see is an illustration using light at longer wavelengths to pick out.
And I'll talk about what that means in just a second here to instead take a picture
of the glowing gas and dust that make up the stellar nursery that actually
pervades the constellation of Orion and is certainly serving as the engine that builds new stars and Orion and is making our Milky Way galaxy bigger.
So the thing that you see on the right is a picture of glowing dust in galaxies is a picture of glowing dust.
You see the same Orion constellation illustrated here.
And what you can see is that this region that looks empty on the sky to us or dark on the sky to
us with just a few bright young stars hanging off the belt is actually full of shining dust.
And this dust is shining, but it's incredibly cold. It's only about 20 degrees kelvin, so just above absolute zero.
And it's dense enough that we're able to see it glow prominently in both the light that I'm showing you here, which is the glow of dust.
And I'll say a little bit more about what that is in a couple of slides,
but we also see it glow and all sorts of terrible poisonous molecules that form as a result of the gas being very well shielded,
protected from from destructive light by the dust and being dense enough to form molecules.
So let me just for those who are who do not have a non optical astronomy background, which is almost everybody, let me just emphasise that.
So I'm going to talk in this, I'm going to freely use the words microwave sub.
Mm mm. Am long wavelength and all of these things just refer to observing the universe with light,
but it's light that is lower in energy and a little bit different in character,
meaning that it has low energy,
it passes through things easily and it's easier to generate with cold objects than the light that we see with our eyes.
But this this long wavelength light, which is a type of radio waves,
travels at the speed of light and otherwise behaves just like the light that we see with our eyes.
So the advantage for using this kind of light to study the universe is that you can see things like the very cold gas that pervades the Orion.
The constellation of Ryan is forming these young stars. Or you can see the glow of a whole suite of terrible poisonous molecules.
And because, as I'm sure you're familiar with, your radio waves can get inside your house and so can easily pass through intervening material.
This also turns out to be a very good way to look through the dust that blocks the light from the stars and material deep inside the Orion Cloud.
So hopefully this makes sense. And what we would really like to do if we want to understand how stars, galaxies, planets are born,
is to study this long wavelength light that comes specifically from cold, dense material.
It's about to form the next generation of stars and planets,
and we would like to take pictures of the structures that are giving birth to these stars and planets.
To do this, we need to be able to catch this light. We need to build telescopes that see this type of light.
And what these essentially look like are giant versions of the satellite antennas that you may have on your
home to to catch a television or versions of the communication devices that you may see driving around.
But these things need to be able to see through the Earth's atmosphere, which is unfortunately very,
very opaque to the type of the particular type of light that we get from dust grains and molecules
that are exactly the things that are forming the next generation of stars and galaxies.
So the specific problem, which is not exactly the same thing, but is sort of related, is that water in the atmosphere blocks microwaves,
which you might know, although this is a this is a plane a little fast and loose from the fact that your microwave oven heats the water in your food.
So the water in the atmosphere in particular makes the atmosphere very, very opaque to seeing this light.
But we can see it from the ground and in particular, we can see this glow of cold gas and dust.
If we can get up to a site that is high enough and dry enough that a substantial fraction of the water in the atmosphere is below our telescopes.
And you can see that illustrated here in this sketch of how opaque the atmosphere is as a function of the wavelength of light that you're looking at.
And in particular, if you wanted to study, glowing planets are glowing,
forming a glowing planet, forming disks or star forming clouds, stellar nurseries.
You would want to be looking here. And so you can see you can see through the atmosphere a little bit, but it's not great.
So what you like to do is you'd like to go to a very high and very dry site in order to study this type of light.
And this is what people have been doing for years.
So they built arrays of telescopes on places like the top of Monaco, up in the Alps in France.
And as you can imagine, this is very, very difficult.
So what that means is that to date, we have not had truly giant telescopes studying the universe in microwave light.
And so this is where the Atacama Large Millimetre Submillimeter array comes in.
So this really blows the door off this field by essentially giving us our first.
You can think of this as a Hubble class instrument to study the universe in microwave light.
And so as I mentioned at the beginning of the talk by several metrics, this is the biggest, most complicated.
And although this shouldn't necessarily be a point of pride, most expensive telescope ever built on the ground.
And so the idea is that the reality is that Alma is observing the universe in microwave light with both a sensitivity and
a sharpness of view that is essentially ten times better than any previous telescope studying the universe in this way.
So to give a couple of specifics and then I will show you a couple more pictures.
Alma is an array of 66 antennas. So these things have all been so they're individually about 12 metres across and they've all been carefully machine
so that the surface accuracy of the thing is almost a perfect parabola to within something like ten microns.
And behind this array of 66 antennas is a massive supercomputer that in real time combines what
all of the individual antennas see and gives us these fantastic pictures of the universe.
And this would be impressive on its own.
But the really impressive thing is that this fantastic collection of machinery doesn't live just anywhere but live.
So I said that we want to place the telescopes that study this microwave emission in places that are high and dry.
And Alma essentially picks out the place that the place where you could build
an array that is highest and driest without heading down to the South Pole.
So Alma is built high in the Chilean Andes. So as part of the Atacama Desert specifically, it's on the charge.
We're on to our plateau, which is a flat enough piece of ground at an elevation of 5000 metres so that you
can both build an array and be above an enormous fraction of the Earth's atmosphere,
meaning that the light from the forming planets and stars and galaxies is not blocked
out by nearly as much of the atmosphere as it would be if you built these telescopes.
At lower elevations. And you can see your comparison here.
Alma is although there are smaller telescopes at higher elevation, Alma is really the highest big telescope in the world.
So you have this fantastic machine in a high and dry place.
And I said that it takes very, very sharp pictures.
I do want to emphasise that this array isn't just 66 individual antennas all doing their own thing.
Instead, when you. One of the neat things about using this particular type of light is that when you see these arrays of dishes,
but you also see pictures of they're all staring in the same direction for a reason because
essentially these 66 antennas are all able to work at the same time as part of a bigger,
single, coherent telescope. There are some pluses and minuses to doing things this way, but it's a little bit like taking a metre,
scattering it and saying that you can still see the reflection in the mirror.
And it's really like imagining that you've built a great big telescope that has
the size equal to the area under which you've scattered all of these antennas,
and then saying that I'm going to just knock out most of the area in there.
And it turns out that with a little bit of math, which is done by that supercomputer that I mentioned,
you can then still use this essentially sparsely sampled version of a single giant telescope to take
pictures that are just as sharp as they would if you had a telescope that was not 12 metres in size,
but a kilometre. Or when you throw these things out to the maximum distance afforded by this plateau, a telescope that's 15 kilometres in size.
So the trick here is to drag a whole bunch of very, very precise, individually awesome telescopes up to 5000 metres,
find a piece of ground that is flat enough to spread them all out across ten kilometres and then attach a computer that when it was built and this is,
you know, Warsaw calls this but when it was built was one of the most impressive pieces of computing hardware in the world.
Attach this to the back of it to get them all working together as a single telescope that gives you these incredibly sharp images.
So the idea then is that you have this group of telescopes working as an array
with a size that is effectively between as much as 15 kilometres across.
And let me just say in a little bit more detail quickly, what you can actually use this fantastic piece of machinery to see.
So I was a little glib in the beginning and said Forming stars, forming galaxies.
So I'm specifically really good at looking at two things.
There are some it can do quite a few other things, but it's really good at doing two things.
And so the first of these is looking at the glow of interstellar dust.
So there, as Martin mentioned, there's this.
If you go out into the Milky Way galaxy and you move between stars,
that space is not totally empty, although it's it is quite empty by terrestrial standards.
It's instead full of hydrogen and helium, but also other things carbon, oxygen, the heavy elements that make up our body and the earth.
And a lot of those heavy things live in tiny, little sooty grains that are maybe a millionth of a metre across and that what we call dust,
but with a look more like soot, if you can put it on your fingers. So that soot lives between the stars.
And it's the reason that interstellar clouds look dark and starlight.
If you've ever seen a picture of the Milky Way, you've seen these dark lanes running through it.
This is you can see this in the first light that I showed.
And so that that dust blocks out the light of stars that hits it.
But that energy can't go nowhere. So instead, the dust heats up.
Although it's by no means hot, it heats up to temperatures of something like 20 degrees above absolute zero,
but something that's 20 degrees above absolute zero. It turns out to be really good at glowing in the type of light that Alma can see.
So almost very good at snapping pictures like this where you look at the glow of the dust between stars.
And so you also see the gas between stars. And it turns out that the stellar nurseries that form stars are huge condensation of interstellar dust.
And so Alma turns out to be very good at looking at the structures that form stars and planets, because they tend to be full of interstellar dust.
So the other thing it does is it looks at gases that will mostly kill you.
So in these very dense regions that are likely in interstellar space, that are likely to form the next stars and planets,
that hydrogen and helium isn't just floating around by itself, it's floating around and it is bumping into other atoms.
And as it does this, these regions are dense enough and cold enough, and they are protected from the kind of light that when bust molecules apart.
And so these atoms combine into molecules and these molecules are things like carbon monoxide, cyanide,
formaldehyde, ammonia, basically nothing that you would like to actually be locked in a room with.
But this is it turns out that these things are pervasive in interstellar space and Alma is very, very good at seeing them.
So at this point, there are between 102 hundred total molecules known in interstellar space, with more of them being seen every year.
And in addition to being able to see the dust between stars.
Alma is very good at picking out the molecules that live in the densest and darkest parts of interstellar interstellar space.
And I will force a little bit of quantum mechanics on you to tell you why it's very good at seeing this.
So these molecules can spin and vibrate and in particular when they spin.
So when you will take the example of carbon monoxide here, when one of these molecules spins,
it turns out that quantum mechanics says you're only allowed to spin at certain rates and is you
shift the spin of the molecule from a faster spinning molecule to a lower spinning molecule.
You drop the overall energy of the molecule. And again, that energy has to go somewhere.
And where it goes is out in light with a very specific wavelength or frequency,
one that we know for simple molecules like this very well from either calculations or the laboratory.
And it turns out that the type of light that's emitted by all of these terrible interstellar
molecules lines up exactly in the range of types of light that Alma is very good at catching.
So Alma is excellent at taking pictures of the molecules that pervade the densest and coldest parts of interstellar space.
And so you get pictures like this, which is a picture of a very nearby nursery that's currently forming stars.
The total image is a few tens of light years across. I'll show that again in a couple of slides and you can see all sorts of fantastic
structure and figure out why the next generations of stars are being born.
You'll also notice that this image is coloured with blue and green and red colours.
So that's actually showing you the third thing.
And the last thing that I'll mention that Alma is very good at measuring, which is how fast that gas is moving towards us or away from us.
And so I mentioned that that light comes out with a very specific frequency.
And so the molecules are only allowed to spin at certain rates.
And we know exactly the type of light that's emitted.
So you're familiar with the Doppler effect from everyday life,
as this is the effect where an ambulance giving off a particular frequency as it comes towards you,
you hear it higher pitched and as it moves away from you, you hear it lower pitched.
So there's many applications of this in everyday life. Exactly.
The same thing goes on with light from these poisonous molecules.
So as a carbon monoxide molecule moves towards you, you see the light from it at a slightly higher frequency.
And as it moves away from you, you see it at a slightly lower frequency.
So the result is that whenever Alma takes a picture of one of these regions
that are forming stars or planets in it and looks at one of these molecules,
we actually learn about the motions of the gas as it comes towards or away from us.
And this also makes it a very effective machine to, for example, try to weigh things or watch the motions induced by gravity.
And so I'll show you a couple of examples of that later on.
So let me now shift gears to tell you a little bit about what we've actually found.
So I mentioned that Alma has been sort of blowing the doors off of a number of fields.
And so I just want to take you through a few of the things that have been done and maybe about to be done that I think are most exciting.
And so the first of these is that the formation of planets, I would say, is the most exciting results on the formation of planets that we've had.
And I will probably not even slightly exaggerate in decades have come from pointing Alma at the places where we know that planets actually form.
So these are two artist's conceptions. So the idea that we have in our head and this goes back to contain the 18th century,
is that the solar system forms out of a spinning disk of gas and dust,
and these spinning disks of gas and dust formed naturally as a result of this sort of collapse of gas down the form of the sun.
And if you've seen pictures of the solar system, you see that the planets are all more or less aligned in a plane spinning in the same direction.
So we have quite good indirect evidence for this idea that planets are forming out of disks around young stars.
And then over the last decades, we've been able to see but not take sharp images of the disks that we think form planets.
And what Alma has brought to the table for the first time is the knowledge, not just that there are disks forming planets around young stars,
but the ability to actually take detailed pictures of the places where planets form.
And so for a lot of astronomers and not only people who are aficionados of arrays of telescopes,
some young may find this picture here on the right, which is a picture of a the planet forming disk around HL 12.
So this is a nearby very young so less than a million years,
potentially just a couple of hundred hundreds of thousands of years old star with one of the brightest disks that we have available to us in the sky.
So this is the planet forming disk around a very young star.
What you're looking at is the glow of the dust that I mentioned.
And instead of just being able to tell if there's a disk there, you see the stunning structural gaps and bright spots,
which is almost certainly directly related to the formation of planets in this disc.
The initial thought was that perhaps planets were clearing out the rings in this disk.
At this point, people have looked and are able to rule out planets within some of these gaps.
And so some of the current thinking is that instead what you're watching is the formation
of the thick rings of dust that will potentially form future generations of planets.
But in either case, the stunning thing here is that you have a snapshot of the birthplace of planets that has sharper you know,
that is sharper and more detailed than anything we've had before.
And in many ways, as much this image is much more beautiful than these artist's conceptions because it's it's reality.
This isn't the only very cool thing that we've managed to learn about the formation of planets.
So if you think about the planets in our own solar system, there is a very clear pattern to them.
The rocky ones like Mars and Earth and Venus and Mercury.
They all live close to the sun and the big gassy ones Jupiter, Saturn, Neptune and Uranus all live out at large distances from the sun.
And a prevailing idea for why this is actually the case is that in the outer parts of
one of these disks that are going to form generate the next generation of planets,
that the conditions are colder.
And so these molecules, these things like cyanide water, can condense out of the material, out of the planet forming disk and can give you a very big,
solid core that is likely to serve as the seed for growing something big like Jupiter or Saturn in the inner parts of the solar system.
The thinking is that if you can't have access to the ices that you get from freezing these molecules out of planet forming disk,
then you are likely to not be able to form a core that is big enough,
quick enough in order to capture a gas from the surrounding disk before the
young sun becomes a jerk to the surrounding desk and just clears it all out.
So there's a there's a big thinking that where you can form ice,
where there has been a big idea that where you can form ice in a planet forming disk is a driver of the planets that could come out of it at the end.
And excitingly, again, this is an idea and it's an old idea,
but Alma has given us Alma has moved towards giving us the ability to take direct
pictures of where ices form and don't form in the disks that form planets.
So I'm showing you an example here.
Again, it's an artist's conception of the icy outer part on the left and the not icy inner part on the on the inner part.
Sorry. On the left, you see an artist's conception of the icy outer part and the not icy inner part.
On the right, you see an actual picture, which again is stunning if you are looking to actually see this effect in nature.
And so what you see, this is the disk that's forming planets.
There's a young star named Hydra at the exact middle of this image.
And what you see on the left is an illustration of the overall disk, of the overall structure of the disc.
In the middle, what you see is the distribution of carbon monoxide.
And then on the far right, you see the distribution of a chemical that only appears after a carbon monoxide has disappeared.
And so this tells you that all of the carbon monoxide that you see in here has vanished onto the solids that we think
might be seeding the formation of the next generation of Jupiter's over Saturn's in this disk around this young star.
So carbon monoxide freezes out at a pretty low temperature of 20 Kelvin.
So you see this transition very far out from the parent star with a great deal of effort.
This has also been seen, but the picture is a little less pretty for water in one nearby star,
although it's only captured when that star essentially emits a great big burp
of light that temporarily pushes the location of water far out into the disk.
But we can actually see the lines that we think are the chemical lines that we think are related to where you could form
giant planets in these disks or where you're going to be stuck forming planets potentially like Earth in these disks.
So I'll just say, you know,
this is these examples of seeing our ideas about how planets formed turned into beautiful pictures of individual disks are extremely exciting,
but the place that the field is going right now is to try to see many of these frost lines or snow lines in planet
forming disks and to see the many of these telltale type gaps and structures in the disks that form planets.
And the thing that's driving this is if people if you've read about the Kepler satellite or similar efforts,
we now have a reasonable handle on the demographics of the planets that live around us in the Milky Way.
And the big thing that Alma is working on trying to do by studying these disks around young stars is to try to put together
a picture of how you actually form the distribution of planets that are seen by satellites like the Kepler satellite.
So the direction that this field is going is in trying to give us a complete view of how planets form around young stars.
Now that we've seen some of our idea that some of our first ideas validated or challenged by observations.
So I will just say a couple of words about the other end of the universe, too, since the these pictures are much.
Pretty than the pictures of planet forming disks.
But that's because these are some of the most difficult, most most difficult and most important observations that Alma can make.
And that's taking pictures of the formation of galaxies at the others on the other side of the observable universe.
So this has also been a huge area for Alma's first few years.
And the idea is that we can learn an enormous amount about how the first generations of stars were born in galaxies and how most of the galaxies
that we see around us were actually built up by studying the gas and dust that are actually forming stars when the stars actually formed.
And so we know that the first galaxies are born within a billion years after the Big Bang,
and that most of the stars in the galaxies formed between six and 10 billion years ago.
And so a huge amount of effort from Alma has gone into taking pictures of the galaxies that we think are right now, meaning 5 billion years ago,
but catching the light from the galaxies as they actually build up most of their as they actually build up their stellar populations.
And so maybe the most spectacular example of this here is here, which is taking this picture,
Hubble's picture of nothing that I showed you at the beginning of the talk,
showing us a universe full of galaxies that's in purple here and in orange.
What you see is a picture with Alma of the same region showing you blazing
reservoirs of gas that are actually forming new galaxies in the same region.
And not just from these observations, but from a lot of observations that and I want what I want you to see here in that stream,
the capabilities of both Hubble and Alma.
We've managed to build up a picture where we understand that a lot of the build-up of galaxies, which occurred mostly again,
10 billion plus or -1,000,000,000 years ago, occurred because these galaxies were richer in gas.
And that gas is something that Alma can see. And so what you can see here qualitatively is that in the background,
this picture with Hubble of stars from galaxies that are 10 billion light years away.
And the similar picture in gas from Alma. So they both show us, you know, some details of the formation of stars in these objects,
but they're both absolutely straining the capabilities of the telescope.
If you think these just look like smudges and not beautiful pictures of galaxies, you're absolutely right.
So these are things that are forming stars a thousand times more vigorously than the Milky Way galaxy,
but they still just look like little smudges at the edge of our ability to take pictures with Alma.
So I will again show you probably the flashiest example of using a trick provided to us by nature
to break this and take a detailed picture of a galaxy as it's actually in the process of forming.
And that takes advantage of a trick that is given to us essentially by general relativity.
And thanks to Einstein, we know that mass curved space and that also curves the path that light follows and allows
the gravity created by galaxies or clusters of galaxies to act as a additional lens,
focusing light to us and making background objects brighter.
So this lets you take your best telescope in the world that can only just barely see the formation of these galaxies and take advantage
of an extra giant telescope that's been provided to you in space by the presence of a lucky super position of a foreground object,
focusing the background light from these galaxies to you.
And so there are examples of this that may be familiar to you if you've seen pictures of clusters of galaxies.
This effect is seen in the optical, and you can see it in these sort of arcane features seen here and here.
And what these are, is these are a dim background galaxy with its light heading off in directions that we would not catch.
But that's caught on a curved path through space time and pointed back towards us by the presence of a large amount of mass in the foreground galaxy.
And so you can see that illustrated a little bit here.
But the really cool version of this and the most spectacular picture that all my has taken of a distant forming galaxy is here.
And so the thing that you see on the left is a picture of a relatively low mass galaxy with the poetic name of ESDP 81.
This thing looks like a ring, but it's not a ring.
What this is, is it's an example of light that was heading off in many different directions.
That's been caught by a galaxy between us and the background galaxy and bent back towards us.
And so the result is that we see light coming in from these different directions where the path has been diverted as a ring.
And the reason we don't see anything at the middle is because this galaxy that's bending the light is not full of gas and dust.
On the right, you can see a picture of the distribution of stars and the ring of dust seen from the background galaxy.
So you can use this,
the fact that the galaxy is brightened because you're getting way more about it than you would expect to make a very precise picture of this galaxy.
It takes a bunch of math and there is a mild amount of sketchy ness to this.
But what you see is a galaxy that would be far too tiny for us to study that at the
distance that it actually sits at sitting again many billions of light years away.
And what you see is a bunch of stellar nurseries that are far more active and vigorous than anything like Orion that we see around us today.
So tiny little things, tens of light years across, but that are collectively forming stars that are eight 100 times the Milky Way.
And what you see again here is that the resolution with which you see these,
the sharpness of the image that you can get thanks to the presence of the gravitational lens,
is vastly higher than what you would get either from Alma alone or even trying to study the same object
without the aid of the intervening gravitational lens from the space from the Hubble Space Telescope.
So I want to spend one slide just pointing out that you have local people doing amazing things with
Alma and this takes advantage not of the not of just being able to see the dust or see the molecules,
but that ability to harness the Doppler effect that I mentioned,
because you can tell very precisely how fast these molecules are moving towards or away from you.
Alma is a very, very good machine for measuring how fast gas moves.
And if you go look at the centres of galaxies, we know that most of the centres of galaxies,
including our own milky Milky Way harbour giant supermassive black holes.
So in our own Milky Way, this is a thing that's about 3 million times the mass of the sun.
The biggest ones get up to billions of times the mass of the sun.
But there are a huge number of mystery surrounding these black holes at the centres of galaxies, and a lot of that is because they're black holes.
It's very hard to just point and say, oh, you know, in this part of this galaxy, there is a black hole with this much mass hanging out here.
So unfortunately, you generally need something moving around it, which is the trick that's used here,
or you need something to fall onto it in order to see the presence of a huge black hole.
And so it turns out that Alma, by watching the disks of gas that tend to form in the inner parts of galaxies rotate under the gravitational
influence of the black hole gives you one of the best ways to weigh black holes in the centres of galaxies.
And so team led out of led out of Oxford has been using this to essentially deploy an
entirely new way to measure the masses of black holes at the centres of galaxies.
And if you want to watch, for one thing, in the next year, I think it's worth staying on black holes and it's worth mentioning.
So this is something with Stephen Hawking passing away today.
It's something it's very nice to mention that there is an amazing discovery regarding black holes potentially coming just down the pipe from Alma.
So it's very neat to measure their masses.
But Alma is actually the linchpin in the opportunity to take the first direct picture of a black hole and the way that that is thought to be possible.
And we're hoping that it's possible is to use this broken mirror trick,
the ability to use telescopes in concert as a telescope that is effectively much bigger, that is acting like the size of the array that you're using.
But to take this up from just using a part of, you know, of the desert in the Andes to now using the whole Earth as your effective telescope.
And so the idea is that by combining observations from Alma, with observations from Mexico and Hawaii and the South Pole and Spain,
you can build a telescope that can take pictures with a precision as though it had the size of the entire earth.
And that turns out to be almost exactly the right size of a telescope in order to see the black hole at the centre of our galaxy.
So this is not a picture that Alma has taken that we know of.
So but this is a simulation of what the black hole at the centre of our galaxy, which is 3 million solar masses,
might look like as a cloud of gas falls onto it and that gas heats up and the light from that gas is bent as it comes towards us.
And the result is that you see a you essentially see a shadow that amounts to the
location of the event horizon of the black hole at the centre of the Milky Way.
So people have speculated about the ability to see this for years.
The observations have been taken. So the teams have these observations, and if they actually come through with this,
this would be the first direct picture of the event horizon of a black hole, which would be really incredible.
So far, they are not telling us what they've seen.
But you should absolutely keep your eyes peeled for a headline coming perhaps any day or any month or you know,
given the way things actually work, what is much more likely is that they will say they need a little bit more time.
But some year here, we should get we should have the prospect of actually seeing this picture.
So let me end by showing you a few slides,
showing you what the way that my collaborators and I have been using the telescope and the stuff that we have been here discussing all week.
And that's perhaps a little bit mundane than taking a direct picture of a black hole, but still very fundamental.
And so what we're trying to do is to study how the nurseries that form stars depend,
how the nurseries that form stars form live, die, and how they vary from place to place across the universe.
And so I flashed pictures of the Taurus Stellar Nursery in the Orion Stellar Nursery a couple of times.
But let me actually say a couple of words about what these things are.
So we think that essentially every star and every planet formed in a cloud of dense, dark, cold gas,
these things tend to be held together by their own gravity, and they tend to be a few tens to 100 light years across.
These stellar nurseries sort of represent the densest clumps of material sitting inside the gas between stars.
And Alma is very, very good at picking them out. And so you see pictures here of two of the ones that are nearest us.
But what we haven't really been able to do up until we turned on this telescope in Chile
is to go across the entire set of galaxies that we see around us in the universe and say,
not only, you know, how do stellar nurseries look, not only looking a paltry 150 light years away or a paltry 80,000 light years away to Orion 1500.
But how did how do Stellar Nurseries look as you go to other galaxies?
How to stellar nurseries look in the inner parts of galaxies, the outer parts of galaxies?
And how have they changed across time? How do they live? How do they die and how are they formed?
And essentially the way that we are doing this is to take pictures of the gas across the entire face
of all of the galaxies within 60 million light years that are actively forming stars right now.
Reasonably big that Alma can see. And to see why this is a big jump.
Let me show you the picture of the last time that. A group of astronomers tried to do this something like 15, 20 years ago.
So this is the last time that we used a big array of telescopes to try to take pictures
of essentially all of the galaxies that you could see within some limited distance.
And what you're seeing here in red are pictures of the gas that we think is in individual stellar nurseries in these galaxies.
And this is now pictures of the same two galaxies, but taken using Alma.
So each of the dots here corresponds to one of those places like Taurus or Orion that's
likely to give birth to a new generation of stars and make these galaxies bigger.
And the jump here is astounding. So we're able to go from really struggling and really doing very hard work to, you know,
take a relatively course picture to fairly easily taking a picture of all of the stellar nurseries across each of these galaxies.
And the result is that what we expect to be able to do is to put together a picture of
something like 100,000 of these stellar nurseries across all of the nearest hundred galaxies.
And for those who have a penchant for for those who have a penchant for sort of older astronomical books.
A little bit what we're trying to do, if you're familiar with these sort of beautiful pictures of galaxies from the Hubble Atlas,
of galaxies put together by our standards in about the middle part of the century,
is we're trying to build the first sort of book of galaxies that you can see as looked
at in the millimetre that have the same quality of images as you see in optical light.
And to really learn about where where stellar nurseries live in their galaxies.
So I mentioned I want to show you one movie and then a couple more. Pretty pictures on this, too.
Just too close. I mentioned that when we take pictures of this gas, we also capture its motions.
And so that's exactly what we see here. I will.
So what I'm showing you here is a picture of a galaxy on the left and then on the right.
What you're watching is a fly through of the galaxy where each individual frame shows a different speed of gas coming towards or away from you.
So as we take pictures of these galaxies, we also get we also capture how fast the gas is moving towards or away from us.
And if this looks confusing, then I think this is probably a nicer way to see it.
So as we take pictures of these galaxies, we not only see where the stellar nurseries are,
but we watch how the stellar nurseries are moving and how the gas moves inside the individual stellar rings.
And so what you see here are images of how fast the gas moves across the face of both of these galaxies that I've been showing you.
And the main motion that you see here is just that this gas moves away from you and this gas moves towards you.
So what you're looking at are tilted, spinning Frisbees with the rotation of the gas here,
driven by the gravity of the stars and the dark matter in the galaxy.
But there's a lot more subtle motions here related to the arms at bars that relate to how you're pulling
the gas together and forming these stellar nurseries and then tearing them apart that are fascinating.
And I will close by just saying a couple of words on what we found so far.
But this is really you know, this project right now is delivering.
It's taking its observations and sending the data using up a big chunk of the Internet
pipeline between Chile and North America and then piping stuff to us sort of day by day.
So this is really a project that is happening right now at at all.
But we already have the first few images that I'm showing you. And what we see are some really spectacular pictures.
And I really like this picture which combines Alma in purple with a picture of where we know that.
So I'm calling these things stellar nurseries. The picture in yellow is showing you where we know that young stars have recently formed.
And what you see stunningly from this picture is that the it's very clear that the stellar nurseries and the young stars live close to each other.
But it's also the case that the stars that have just formed are not living exactly where you see the star, the stellar nurseries from Alma.
And our understanding of this is that stars are essentially huge jerks to their parents.
So when you form these young stars, these young stars start pouring out light.
When the same winds that clear out protoplanetary disks or the planet forming disks come off of these stars and start hitting the parent cloud.
And then in fairly short order, the biggest of these young stars collapses and explodes as a supernova.
And so what we think is that you're seeing the offset between these stellar nurseries that will form stars in the near future and the places
where young stars have already formed because those young stars have annihilated the clouds that they that actually gave birth to them.
So you see them closely associated, but not directly on top of each other.
And then I would just say by way of sort of, you know,
the other things that we're finding as opposed to showing you a sort of bunch of very technical graphs, I would say qualitatively,
the very neat things that we're finding are that the stellar nurseries do really very dramatically
from place to place as we look across all of the different galaxies in the nearby universe.
And so what we see strikingly is that you get big star,
you get big stellar nurseries with violent motions in the inner parts of galaxies and on the spiral arms that we see.
And in dinky little galaxies, we see them forming tiny, stellar nurseries with comparatively less violent motions.
But overall, the sense that we are getting from these first few, from the first few observations that we've managed to take on this program,
are that it's really it seems very clear that the nurseries that form stars do know about the galaxies that they live in.
It is less clear whether the stars that come out the other end and the planets that come out the other end are deeply affected by this.
But this is something that we hope to have a good answer to within, you know, maybe months, but years, the next few years.
So I would end there and say, I hope that I have at least convinced you that there is a quiet or maybe not quiet revolution
going on in astronomy and specifically this field of long wavelength astronomy or.
Mm. Astronomy is being absolutely revolutionised by hauling 70 of the best telescopes
that we can make up to the most or most remote place that we could take them,
and then pointing them at the structures that form planets and pointing them at galaxies as they're being born across the other side of the universe.
And then using the motions that this thing can see to away black holes ends up at way galaxies.
And then hopefully if you stay tuned, we're also taking the first picture that we've ever had,
of the first direct picture that we've ever had of a black hole.
And still, you should stay tuned and keep an eye out also for what we're learning about how
the nurseries that give birth to stars change across the across the universe.
Thanks.