Hello, and welcome to this episode of the
Physics World Weekly Podcast,
which is sponsored by the Kavli Prize.
I'm Hamish Johnston, and I'm very pleased to
be joined by the astrochemist
and Kavli Prize laureate,
Uwina van Dishoek,
who is professor emeritus of molecular
astrophysics
at the Leiden Observatory
in The Netherlands.
Our conversation is coming up after a word
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In 2018,
Uwina van Dishoek won the Kavli Prize in
Astrophysics
for her combined
contributions
to observational,
theoretical,
and laboratory
astrochemistry,
elucidating
the life cycle of interstellar clouds and the
formation of stars and planets.
She joins me down the line from Leiden.
Hello, Iwina.
Welcome to the podcast.
Hello. It's a pleasure for me to be
here.
So, Ewina, your field of research, it's it's
a fascinating
combination of observational astronomy,
astrophysics,
and chemistry.
Can you give us a brief introduction
to astrochemistry?
Indeed.
My field of astrochemistry
is a combination
of both astronomy and chemistry
and sometimes
even,
other areas,
come in there.
But, basically, what we do is the study
of the formation,
destruction, and excitation of molecules
under the rather
exotic conditions that we have in interstellar space.
So space is very empty. Densities are, say,
a million times lower than the best
ultra high vacuum that we have in a
laboratory on Earth. And also very low temperatures,
and sometimes very harsh UV radiation.
So studying the chemistry under those exotic conditions,
that's sort of the chemistry part of astrochemistry.
But the field is is is actually much
more than that.
There's also an astronomy part,
because molecules actually have an influence on their
environment,
because they are major coolants of the gas.
When you excite a molecule and it emits
a photon
and that photon escapes from the cloud,
then actually the gas cools down.
So they actually also set the temperature of
these clouds. They can be used as remote
thermometers
through the excitation.
They are also exquisite tracers of the kinematics
and dynamics of clouds.
So astronomy wise, there is a lot to
do with molecules, and,
astronomers are now using that to study,
the gas not just in the Milky Way,
but even molecular gas at the edge of
the universe in very distant galaxies.
I see. And my understanding is that most
of your work is is theoretical
astrochemistry.
Would that would that be right? You're you
don't spend all of your time
in the lab
like we would think of as a
a a traditional chemist. But
I'm just wondering
how
how you make the connection? How how can
you make the connection with the sort of
chemistry that we do here on Earth
and the chemistry that occurs in the cosmos?
Because,
you know, as you've alluded to, it it's
a very different place, isn't it, in terms
of density and radiation and
all that sort of stuff?
Yeah. So indeed, I started actually out as
a theoretical chemist
before I even knew of interstellar space and
the molecules there,
quantum chemistry.
So that was the very early part of
my career.
And then over sort of the last decades,
I have become much more involved in observations,
and also indeed to some degree in laboratory
experiments, at least,
overseeing and supervising a number of the the
laboratory
experiments that are going on in Leiden.
So there are lead challenges. So on the
one hand, you know, sometimes you have molecules
in space that you don't even have on
Earth. So,
they're,
very short lived. Radicals and ions are very
short lived under Earth conditions, but they can
be very stable molecules in space. And so
then it's very good actually to study them
in a computer because the computer doesn't care,
whether where the molecule is. And so we
have learned a lot about that, for example,
of how molecules,
fall apart under the,
under UV radiation.
So, the process of photo dissociation. So that
has been one aspect that was very well
suited
for studying both
here on Earth, but also
in space.
Other
aspects like laboratory experiments, like we do in
Leiden,
there the temperature is is not so difficult.
We can reach the very low temperatures in
the laboratory, and we can freeze out molecules
on the surfaces there. We can study their
spectroscopy
and directly compare that with what we see
in space. That's actually what we use to
identify molecules in space,
study the spectroscopy,
in,
here in the lab because the the laws
of quantum mechanics are basically the same on
Earth
and, and in space.
So that works also very well. What doesn't
work so well is the time scales.
Chemical process
in space can take maybe, you know, hundreds
of thousands or a billion years.
And and, of course, on Earth in our
lab, we want to do it in a
few hours, at least within a day.
So that means we're always working at higher
densities than in space, and we have to
extrapolate that,
to the conditions of space. But there there
are ways of doing that.
I see. And and what are some of
the the important unanswered questions
in astrochemistry
today? What are what are you and your
colleagues really keen on,
on discovering?
Right. So there there are some questions in
terms of chemistry.
For example, we now think that many of
the important molecules like water and also some
of the more complex ones
are formed primarily on the surfaces of these
tiny little dust grains,
micron sized silicates
and carbonaceous material that is,
in this, class between the stars.
These grains are not catalysts in a chemical
sense, but they are sort
of bring the various atoms and molecules together
in a sort of meet and greet,
sense,
to form new molecules. But how exactly does
this happen?
That is a big question.
We've also seen some of these,
large polycyclic aromatic hydrocarbons
in space, whole, families of them even,
in very distant galaxies.
But some of these molecules like
cyanobenzene
and even cyanopyrine,
detected by other groups,
are now found and in very cold and
tenuous conditions, how do you make them there
already? These complex, you know, pyrene four benzene
rings.
How do you make them in research,
cold and tenuous conditions?
But I think the biggest question
that,
we have the overarching
questions,
I would say, of our field is,
the chemical evolution of the universe.
For example, at the very highest redshifts, which
molecules can be formed there?
If, say, half a billion
years after the Big Bang, you have much
less carbon and oxygen available.
Yet we know that our molecules there.
What kind of molecules do you make? What
role do they have?
And then
one of
the, big questions that certainly,
is not a focus of much astrochemistry
research
is much closer to home.
The chemical evolution from these
telesus clouds to planets. We now know that's
the you know, our galaxy is teeming with
planets. On average, every star has at least
one planet.
You know, what sets the chemical composition of
these exoplanets,
and their atmospheres?
You know, what is basically the root of
these molecules
from clouds to planets?
And I think that is a a very
big question that will,
is being tackled now, and it will certainly
still take some time to to answer.
I wanted to ask you about exoplanets because,
you know, over the past thirty years or
so, there's just been an explosion
in the number of exoplanets that have been
observed, and
our understanding of exoplanets has gone from pretty
well zero
to, well, we know that there's a lot
of them out there.
It is I mean, that must have been
very exciting,
for you and your colleagues
in astrochem chemistry to see.
I mean, in a sense, it's it's a
whole a whole new field really has emerged,
because of these exoplanets.
Yes. Absolutely.
And,
it is interesting
that, of course, it started that revolution in
1995
that was actually the same time that also
these planet forming discs
that had been postulated for centuries, you know,
by Kant, Laplace, Swedenborg,
that these planet forming disc, the rotating discs
of gas and dust, around young stars in
which the planets are made were finally being
discovered and imaged and,
studied. So this has gone,
actually hand in hand. On the one hand,
the discovery of exoplanets and that field now
shifting from
discovery of exoplanets
to actually characterizing them, characterizing their chemical composition
To at the same time,
these discs being studied with, you know, increasing
detail,
with various telescopes. So it's it's a very
interesting sort of two tracks that have been
going on and that are now, you know,
starting to come together.
Yeah. That that that's fascinating.
Can you talk a bit about the research
that you're doing right now? What what what
are you up to in Leiden?
Yeah.
So, lots of things are happening, at this
moment.
If I take a small step back, I
would say that in the the first decades
of my career, we have been focused mostly
on studying this chemical evolution
from the clouds
to these protoplanetary
disks. We've been studying the ice composition,
a simple molecule, simple ices like water, carbon
dioxide,
and now also the more complex molecules,
both in the gas and the ice.
And what has been happening actually in the
last decade is that we have made a
switch
from,
first clouds to disks and now actually from
disks to planets.
And that has been enabled by the, Atacama
Large Millimeter Array, which has now allowed us
not just to detect these discs, but actually
to zoom in into these discs on on
solar system scales.
And, that we can study the chemical distribution,
there,
and see where the dust and the the
ices accumulate,
and also reveal,
actually, surprisingly rich chemistry in these discs.
And then also at the same time, the
James Webb Space Telescope,
which works at infrared wavelengths,
which actually,
can study the warmer gas in the inner
part of the disk, say, the inner few
astronomical units inside
what in our solar system would be, say,
the orbit of Jupiter.
And that's where terrestrial planets are forming.
And,
that is where we and I also study,
the the the chemistry
of various simple molecules and also more complex
ones in great detail. So so we're starting
sort of to to to map,
these discs and,
both from the inner to the outer part
in more detail.
Sometimes I like to compare this also with,
you know, how Google Maps was in the
early days. You know?
A city was one big blob, and you
couldn't see anything in it. And now with
OMA and to some degree also with JWST,
we can now with OMA, we can now
see the the houses, the canals.
We can sort of see all of the
the structure in these,
these disks and see what is where.
And I I wanted to ask you about,
you know, the possibility
of detecting
life somewhere
other than Earth. I mean, maybe in in
the solar system
or,
somewhere else.
You, you know, have a a fantastic knowledge
of of
astrochemistry
and and I suppose, you know, the possibilities
for the conditions for life to be present.
Do you have any any views about,
you know, sort of life on other planets,
I suppose to put it bluntly? Or, and
has that changed over your career? I mean,
do you think it's much more possible now
that we we that life does exist elsewhere?
So I think the possibilities
are absolutely there. I mean, if anything,
our and I would say that of the
Ontario community,
has
shown that,
water is
available around
all young
forming stars,
in quite significant amounts.
We know that it is transported to these
disks,
to the at least the comets and the
planet forming zones of these disks. So we
know there's water there. We know there's there's
organic material there.
So,
there are a lot of ingredients
present to make
a habitable
world, so to say.
I should
certainly say that most of the research
has come to the point of the
knowing or charting
the chemical ingredients
of the
outer regions of planet forming discs, so say
beyond to the colder outer part, beyond,
Jupiter.
JBST is now learning us something about the
the inner part.
But,
there's still a lot of questions
as to what is happening exactly in that,
region of,
what would be the equivalent of the orbit
of Earth,
say, Mars,
in our own solar system,
what is happening exactly there. But we definitely
know that the ingredients are widely available.
Now to what extent you can then make
life,
I always like to bounce that question to
my
chemistry
and my biochemistry
and biology
colleagues because I'm certainly not an expert in
that.
Some of them say they're, you know, chemistry
will find its way,
and it will make life in some cases.
But,
it it will be it will be hard
to detect. No doubt about that.
And it may take us some time before
we know the answer to this question. So
in that sense, I'm a little bit more
conservative than some of my colleagues who are
much more optimistic that we will,
find that sort of in the next decade.
I see. And you you mentioned two major
observatories that you've been involved with, the the
ALMA,
radio telescope array and the James Webb
Space Telescope.
And and you've been involved in the design
and operation
of these facilities.
Can you talk a bit about
the the challenges that are involved in
getting the,
astronomy community to agree on the parameters of
a new
observatory?
I mean, I've you know, I suppose you
come in you you come at, at it
with your astrochemistry
hat on, but, there's probably
colleagues who are more interested in black holes,
and you've got to agree on on building
an instrument that can do a good job
of,
giving us information about both of those things
and much more. How, I mean, how do
you get
how do you start
with the design of something like,
the James Webb Space Telescope,
and how do you get people to agree
on it? Or maybe in the end, people
just don't agree.
That well, it's a it's a very good
question. Of course, it's one that is the
basis of everything that we do astronomy because,
astronomy is a field that is driven by
new facilities.
I think the first thing to note is
that there is no single telescope that can
satisfy
everybody.
So, you always need
telescopes of different kinds covering different wavelengths regime
covering
difference,
say,
fields of view,
whether you're going for a wide field of
view or whether you're gonna zoom in to
a certain astronomical
object.
So so there's
never going to be one that satisfies
all. But then with Zilla given,
range, if I take the the Almad at
the gamma large BDB array as an example,
there were two main science drivers
that the scientists put together. The one was,
very distant galaxies, basically
studying the gas that makes stars
in,
Milky Way type galaxies, but then at at
high ratchets in the distant universe.
That was an important one to basically
charge the,
star formation history,
of the universe in the critical period that
most of the stars are being built. That
was a very strong set of science case
that, was of interest to a large community.
The other one was these, close to home,
these tiny planet forming discs that basically were
so weak and so small,
that previous instruments could not study them. And
we knew that if we ever wanted to
study planet formation
and,
how exoplanets are formed, we had to know
we had to dive into these disks where
the action is is happening.
So zooming in on on platforming disk on
solar system scale, say, down to the orbit
of Jupiter in the nearest star forming region
was another science driver.
So as as usual, you know, The US
made its plans. Europe made its plans. Japan
made its plans.
And then we quickly realized to scientists
that,
none of these plans could satisfy these science
goals.
And that the only way we could make
it work was if you put them together
in one single worldwide array. Because the the
good thing about an array is that actually
many of the parameters scale not just with
n, but even with n squared. So,
everybody knew that this was going to be
a win win situation.
And that's the first thing. If the scientist
agree, then,
and it was also shown that, you know,
you could even make black people
happy to some degree.
And at other size of the system,
even people studying the sun. So then we
had a big movement,
that said ALMA has to be built.
Well, having said that, then, of course, the
technical and fiscal realities,
come to play. And,
that is where scientists then also have a
a big role in in
ensuring that once those
especially the fiscal realities come in,
that still,
in the end, an array is built that,
can still do those science cases.
Basically preserving,
the science case again, making sure not that
not too much rescoping is going on. But
the science cases, they said, you know, the
the size of the array. We knew we
had to have telescopes that had to be
separated by up to 15 kilometers.
We knew that we had to have at
least 50 telescopes for the sensitivity.
We knew that's,
we had to have a frequency range,
from, say, a 100 gigahertz to 800 gigahertz,
so so covering,
a range of frequencies. So that was all
set by the by the science and especially
by the few science drivers.
I see. And, you know, in the case
of the of a space telescope,
I mean, I I find it amazing that
you can, you know, put something like that
up into space, and you can open things
up, and and and it actually works. Do
is
were you very nervous when, for example, the
James Webb Space Telescope was launched? And I'm
sure there was a few moments there
where a lot of astronomers were very anxious
or worried.
I mean, what was that feeling like? It
must have been
a very
incredible moment, I would imagine.
Yeah. Absolutely.
So, I got involved in, Webb, in the
late nineteen nineties,
as part of the science advisory committees, first
of the European
Space Agency and then of the joint NASA,
ESA, US European,
science advisory committee. And,
at that time,
the mid infrared instrument, MIRI,
was not yet secured on the telescope.
Everybody knew, again, based on these science cases,
one had to have the near infrared camera
and a near infrared spectrometer,
but the mid infrared was considered still an
add on at that time. Now we had
just come out of a, very interesting,
innovative mission, the infrared space observatory on the
European side, and knew the power of the
mid infrared.
Only for the brightest sources, but we could
see sort of the potential
of the mid infrared.
And so that was then the role in
sort of the the early two thousands to,
make the case together,
a group of US and small group of
US and Europe,
and scientists that there had to be a
mid infrared instrument on it.
So by 02/2002,
the mid infrared instrument was secured on, JBST,
but then we still had to to build
it.
And NASA and ESA decided that this had
was going to be a collaboration between,
US and Europe in a 5050,
partnership,
which had turned out to be, actually very
well, worked very well. And on the European
side, we had a as is often done
in European Space Astronomy, a consortium
of countries
and institutes that together then built,
the instruments, each institute delivering a part of
the the hardware.
And so in The Netherlands,
we were responsible for building part of the
spectrometer
main optics.
And, that was actually done between 2003
and 02/2008.
So we delivered our hardware
in 02/2008,
and then it was integrated
in The UK.
The imager and the spectrometer came together. It
was tested, calibrated. And then in 02/2012, it
was shipped to to NASA to to Goddard.
Then it was finally launched in 2021. So
you can see that having delivered our hardware
in 02/2008,
this was a very long ride, and,
we were indeed
extremely nervous,
in order,
you know, to to to see the launch
go well. But then also we knew all
of the steps that had to be done,
in in orbits.
Well, first, it had to get to its
orbits and then the the whole unfolding
of the,
the sunshades
and, of course, the phasing up of the
telescope. But then also,
in April
2022,
turning on MIRI, turning on the cooler because
MIRI had to be cool cooler than the
other instruments.
And to me, that was one of the
most nerve wracking moments. I thought, oh, we
have a telescope.
It has survived the launch, but, you know,
will it be cooled?
And, so I was watching nervously
the temperature,
sensor basically
every every day, you know, going down a
little bit,
until it finally reached its operating temperature. So
so that was
a a particularly,
I would say, interesting stressful moment.
Yeah. Especially after all that
time and effort.
Right. That yeah. Well well well, congratulations
that that that you've got it to work.
I mean, that must have been very satisfying,
but,
you know, I think
sort of fascinated by your work in general
because you're you're looking at things that are
light years away.
And then you're sort of sitting here on
Earth and you're you're doing calculations
and may maybe you're doing some experiments as
well.
And you're
you're making connections between something that's
so distant and, you know, happened so long
ago,
let's
say, with, you know, the the science of
today.
And, you know, I think that, you know,
to to me, that sounds like it must
be very satisfying. So
could you share with us maybe some of
the
the the the highlights of of of your
career? You know, some of the things that
that you were really excited about.
So I I would say that's you know,
every time that
I get a new spectrum
delivered
no. It used to be that you go
to the telescope. These days, you know, you
get your data delivered in your computer. But
still, when you open it
and you see the data, you see these
beautiful spectra,
and you realize
that those photons made it all the way
to my computer,
to the telescope first, to the computer,
after traveling through space, through thousands of years,
or in the case of distant galaxies, billions
of years. I I still get an enormous
kick out of that. It's, you know, every
time I look forward to opening a new
Christmas present.
And some of those Christmas presents have been
really fantastic.
As we mentioned already earlier, water has been
one of the
focus areas of my research,
all the way from the star forming clouds
to these, planet forming discs,
not just
h two sixteen oxygen, but also its isotopologues,
especially the deuterated water.
And together, that tells you
not just how much water there is,
you're forming stars in discs, how it is
transported
nearly an altered to the comet forming zones
of discs.
But sometimes,
you can also learn something from the absence
of a signal.
You can learn that it's, you know, the
absence of a signal can mean that water
becomes invisible because it's locked up in,
say, icy pebbles that are the building blocks
of planets,
making the water molecules invisible.
So some of my students say that one
of my most famous sayings is,
all of the information,
all of the new information
is actually in the weak lines,
not in the strong lines.
So this is something that I've I've learned.
Other surprise has been,
now with JWST,
just very recently.
And we were studying these planet formed disc
in our parts.
Some of them turn out to be very
rich in water lines,
warm water lines.
Some of them in c o two.
We don't understand yet why. Some of them
like c o two and the others water.
But then we found that around very low
mass stars, so say,
stars that are only 20% of the mass
of our sun,
there's actually a very rich,
hydrocarbonate
chemistry going on with, you know, booming in
satellite
lines. Even benzene
detected there,
you know, on scales of,
you know, where the orbit of the Earth
or Venus is.
And that was that is a puzzle that
first of all, you know, one of these
moments, but then also that's, you know, what
can be causing that, that difference. So so
when you have a new instrument and you
have picked such a jump in sensitivity, you're
always gonna find something new. And you don't
know yet what, but you're gonna find something
new.
And, Uwina, finally, I wanted to ask you
about the future.
Are there any,
sort of new observatories
or maybe,
telescopes that have just come online
that you're really excited about? Or or maybe
it's a new supercomputer
where you can do
calculations that you could never do before about
chemistry. Or who who knows? Maybe even a
quantum computer
that could allow you to, to calculate the
properties of of molecules in space. What
what are you looking forward to, you know,
let's say in the next ten years or
so in astrochemistry?
Right. Right. Well, I mean, the quantum computer
is an interesting,
option in the sense of quantum chemistry because
that's really one of the main applications of
quantum computers.
And I'm happy to see
several of my younger colleagues going that way,
and I look forward to seeing that results.
I think there are two,
two aspects that I'm looking forward to very
much.
One is actually
that's,
part of our gap of our knowledge comes
from having no observed tree at the moment
that covers
sort of the
far infrared part of the spectrum. So where
JWST stops and where ALMA starts,
between 3,300
microns.
We had the the ESA led mission,
Herschel,
and that was 2009 to 02/2013.
But technology has now advanced so much that
if you cool such a telescope, you get
an orders of magnitude gain its sensitivity. So
so this is one field that is really
ripe for
a new mission. And then,
the NASA is through its pro plan now
proposing,
studying one mission, the mission. And that will
be great, especially also for studying these, planet
forming discs.
The other one is,
already being built, and that's the Extremely Large
Telescope,
of the European Southern Observatory. I don't know
whether you follow the webcam, but,
the building is there, and,
it's making enormous progress. That is a 39
meter,
optical
near infrared,
mid infrared
telescope on the ground.
So it will have fantastic sensitivity
and spatial resolution even though hindered
by the Earth's atmosphere,
in some parts of its wave flex coverage.
But there we can really now start to
spatially resolve,
you know, some of these,
you know, systems that we are now studying
with Webb. But Webb is fantastic, but it's
only only a six meter telescope with 39
meter
diameter. You can really start to resolve sort
of these planet forming,
regions,
and,
and map sort of the molecules,
and the chemistry in much more detail in
that critical
inner,
region of this where planets are forming.
Well, that's fantastic. It sounds like, lots of
exciting,
things to do in astrochemistry in the future.
And I'm guessing that you would
encourage
any listeners who are looking for a career
in
that straddles what physics,
astronomy, astrophysics, chemistry, maybe a bit of biology?
It sounds like something really interesting to get
into.
Yeah. Exactly. Even some geology is in there
now these days. Yeah. No. I can certainly,
it's a very lively community
Great. Well, thanks so much, Awina, for joining
me today on the podcast, and,
the best of luck with your future research.
Thank you very much for inviting me.
I'm afraid that's all the time we have
for this week's podcast. Thanks to Uwina Van
Dishoek for a fascinating conversation
and to our producer, Fred Ailes.
I would like to extend a special thank
you to the Kavli prize for sponsoring this
episode.
The Kavli prize honors scientists for basic research
breakthroughs
in astrophysics,
nanoscience,
and neuroscience,
transforming our understanding of the big, the small,
and the complex.
The biennial
prize awards $1,000,000
in each of these three fields.
You can play a crucial role in helping
to recognize the trailblazers
in your field by nominating them for the
Kavli Prize
during the global call for nominations,
which is open between July 1 and October
1. Please visit
kavliprize.org
for more information.
The Physics World weekly podcast will be back
again
next week.
Bye.