Kind: captions
Language: en
I would run outside and just lay on the
ground under the southern Milky Way
beautiful right up there and I would
just lay there like the snow angel and
just kind of let my thoughts sort of
pass through my brain and this is when I
personally have the feeling that I'm a
part of it I I belong here rather than
feeling kind of small yes I'm small but
there are many other small things and
lots of small things make one big hole
the following is a conversation with
Anna for about an astrophysicist at MIT
studying the oldest stars in the Milky
Way galaxy in order to understand the
chemical and physical conditions of the
early universe and how from that our
galaxy formed and evolved to what it is
today the place we humans call home
this is the Lex Friedman podcast to
support it please check out our sponsors
in the description and now dear friends
here's Anna for Belle
let's go back to the early days what did
the formation of the Milky Way galaxy
look like or maybe we want to start even
before that what did the formation of
the universe look like
well we scientists believe there was the
Big Bang some big beginning
but what is important for my work and I
think that's what we're going to talk
about is what kind of elements were
present at that time
so the Big Bang left a universe behind
that was made of just hydrogen and
helium and tiny little sprinkles of
lithium
and that was pretty much it
and as it turns out it's actually quite
hard to make stars or any structure from
that that's fairly hot gas
and so the very first stars that formed
prior to to any galaxies were very
massive stars big stars 100 times the
mass of the Sun and they were made from
just hydrogen and helium so big stars
explode pretty fast after a few million
years only that's very short on Cosmic
time scales
and in their explosions they provided
the first heavier elements to the
universe because in that course All
Stars fuse lighter elements like
hydrogen helium into heavier ones
and then that goes all the way up to
iron and then all that material gets
ejected in these massive Supernova
explosions and that marked a really
really important
transition in the universe because after
that first explosion
it was no longer chemically pristine
and that's at the stage for everything
else to happen including us here talking
today so what do you mean by pristine so
there's a whole
uh complex soup of elements now as
opposed to just hydrogen helium and a
little bit of lithium yeah so after the
big bang just hydrogen and helium we
don't really need to talk too much about
lithium because the amount was so small
um and after these very first stars
formed and exploded they and the heavier
elements like carbon oxygen magnesium
iron all of that stuff was was suddenly
present in the gas clouds
tiny amounts only very tiny amounts but
and that actually helped especially the
carbon and the oxygen to to make the gas
cool these atoms are more complicated
than hydrogen that's just a proton and
so it has cooling properties can send
out photons outside of the gas cloud so
the gas can cool and when you have gas
that that gets colder and colder you can
make smaller and smaller Stars so you
can fragment it and Clump it and turn it
into stars like like the sun and the
cool thing about that is that
when you have small stars like the sun
they have a really long lifetime so
those first low masters that formed back
then are still observable today
that is actually what I do I try to find
these early survivors
because they tell us
what the gas looked like back then they
have preserved that composition of these
early gas cloud the chemical
compositions until today so I don't need
to look very far into the universe to
study all the beginnings I can just
chemically analyze the older stars and
it's like unpacking everything that that
happened back then it's very exciting so
to just reiterate so in the very early
days in the first few million years
there's giant Stars that's mostly
hydrogen helium then they exploded in
these Supernova explosions and then they
made these clumps
yeah so the first one is pristine
non-pristine clumps yeah pretty much fun
so it took a few hundred million years
for the first stars to emerge and then
they exploded after a few million years
Kaboom and then it's like I always
consider the universe like a you know a
nice soup and then these first Supernova
explosions kind of provided the salt you
know just a little sprinkle of heavier
elements and that made it really tasty
it's just changed it completely right
and that changed the physics of the gas
so that meant that these these gas
clouds that were you know surrounding
the the Forma first Stars they could now
cool down and Clump and form the next
generation of stars that now included
also little stars
and as I just mentioned the small stars
have these really long lifetimes the sun
has a lifetime of 10 billion years
any star that is even less massive will
have an even longer lifetime
so that gives us a chance to to still
observe some of the stats that form back
then so we are testing the the
conditions of chemical and physical
conditions of the early Universe even
before the Galaxy formed so what's the
timeline that we're talking about what
is the age of the universe and what is
the earliest time we got those salty
delicious soup Clump soups with heavier
elements
well the universe is 13.8 billion years
old well legitly yeah
when I was in high school the universe
was 20 billion years old yeah so the
estimate did you change do you think
that estimate will evolve in interesting
ways or no is that is it I think it's
mostly converged yes because the
techniques are very different now much
more precise the whole business of
precision cosmology by mapping out the
cosmic microf background you know that
that's a marvelous feat
um maybe you know the digits will still
move around a little bit but that's all
right plus the gravitational waves and
all that all the different sources of
data yeah kind of mapping out this
detailed picture of the early Universe
yeah totally and so we think the
earliest little stars formed I don't
know maybe half a billion years after
the big bang right again a few hundred
million years for the first stars to
emerge and then you know took some time
so give or take half a billion years and
um that was the time when sort of the
very first pro photo galaxies formed
early Stella structures Stella systems
from which the Milky Way eventually
formed right so it was the Mickey was
probably a bigger slightly bigger one
and we know today that galaxies grow
hierarchically which means they eat
their smaller neighbors so if you're the
bigger one and have a few a few friends
around you're just gonna
um eat them absorb them and then you
grow bigger and
um so all these these little early Stars
you know kind of came into the Mickey
way through that kind of process
and that's why we find them in the outer
parts of the Galaxy today because
they're just kind of deaf and just left
there since so the old stuff is on the
outskirts of the Galaxy and the new
stuff is in closer to the middle is
there broadly speaking okay yes because
that's where you would look for it so
maybe it's just a step back like what is
a Galaxy what is the part of the Galaxy
I love that question so the Galaxy is
um
assembly of
Stars the Milky Way contains something
like 200 to 400 billion stars and most
of the material and the stars are in the
disk and when we look at the night sky
what we see as The Milky Way band on the
sky that is actually the it more the
inner the next inner spiral arm because
we actually live in a spiral this
galaxies are the Mickey who has a spiral
disc Galaxy
um and we're looking
um actually depends a little bit in the
northern hemisphere we're looking out of
the Galaxy so we're seeing the next
outer spiral arm
and as you can imagine there's only dark
space behind that so we don't see it all
that nice on the sky but if you travel
to South uh to the southern hemisphere
let's say South America you see the make
you and it looks so different on the sky
because that's the next inner spiral arm
and that's backlit by the galactic
center
the galactic center is is a very big
puffy
you know region of gas there's a lot of
star formation that the galactic party
is happening there so it's very bright
and it it makes for this very beautiful
Milky Way on the night sky that we see
so actually if you if you ever get the
chance to experience that I encourage
you to almost like close your eyes while
seeing this and imagining that you're
sitting in this kind of disc in this
pancake and you're just kind of looking
right into it and you can you can really
feel that we're in this 2D disc
and then you can imagine that there's a
top and the bottom and that that we
really part of the Galaxy you can really
experience that we're just not not just
lost in space somewhere but we're really
a part of it and you know knowing a
little bit about the structure of the
Mickey wear really helps do you feel
small when you think about that when you
look on that spiral on the inside of the
Milky Way and then you look out to the
outside like how are we supposed to feel
I I don't know I I don't feel small
necessarily I feel in awe and I feel I'm
a part of it because I can really feel
that I'm a part of it
um I think for many people they think
like oh that's just the planet and then
there's nothing and
that's almost a little bit sad but
that's really not the case right because
there's there's so much more and I
really like to imagine wow I'm I'm
sitting in this big Galactic
Merry-Go-Round and we're going around
the center and I can see the center
above me right and I can almost feel
like we're going going there
um of course we can't really feel that
but the sun does Circle the galactic
center but there's a kind of sadness to
like looking pictures of a nice vacation
place
all we get is that light and old light
is do you feel like sad that we don't
get to travel or you and I will not get
to travel there and maybe humans will
never get to travel there yeah I always
wanted to travel to space and see the
Earth and other things from from up
there there's there's certainly that but
I don't know it's it's also okay it
would just be at our vantage point and
and see it from from here with the
sensors with the telescopes that we have
and explore the possibilities yeah I
mean there is a kind of wander to the
mystery of it all what what's out there
what interesting things that we can't
possibly imagine you know there could be
all kinds of life forms bacteria all
this kind of stuff I tend to believe
that
um
you know it depends on the day I tend to
believe there's just a lot of very
primitive organisms just spread out
throughout and they build their little
things like bacteria type organisms
um
I used to think what kind of Worlds
there are because they're probably
really creative living organisms
because the conditions I guess the
question I'm
wondering to myself when I look out
there to the Stars how different are the
conditions on the different planets that
orbit those Stars it will definitely be
very different I mean the variety out
there is is huge we know now that I
think it's about every other star has at
least one planet
I I already mentioned the number of
stars in the galaxy I mean you know
that's it's a huge number of planets out
there so who knows what that looks like
all we know is that there's
there is a lot of variety we don't quite
yet understand
what drives that what governs that why
that is the case why is it not all one
size fits all right maybe the Dynamics
of Planet formation like exoplanet
formation or Star formation the whole
all of it all of it
our formation is remains a much research
topic
it kind of we definitely know that it
works because all the stars are there
same for the planets but the details are
so varied per gas cloud right
um it's very hard to to come up with
very detailed prescriptions broadly we
have figured it out you need a gas cloud
you need to cool it
something clumps and fragments and
somehow it makes a star with planets or
without but the Dynamics of the clumping
process is not fully understood no no
and and the local conditions are so
varied right I mean it's the same with
you know all people look like people but
individually we look very different so
even the subtle diversity of the
formation process creates all kinds of
fun yes so you we just don't know how
this turned out in an individual case
and it's kind of hard to
to figure it all out and and to take a
look certainly with planets right the
chance forever to ever actually take a
picture of a planet is minuscule because
they don't shine so they're really dark
yeah so I'd say there's there's a lot of
possibility out there
but we have to be a little bit more
patient before we come up with
Technologies where patience becomes less
necessary by extending our lifetimes or
or increasing the speed of space travel
all the kind of stuff he was a pretty
pretty intelligent they're pretty uh
sometimes yeah for the most part I hope
and now when I'm on the optimistic days
well maybe just to linger on the on the
what a galaxy is
um what should we know about our
understanding of black holes in the
formation is that an important thing to
understand in the formation of a galaxy
like uh so all the orbiting all the
Sparling that's going on how important
is that to understand all of the above
that's what makes astronomy really hard
but also really interesting right no day
is like another because we always find
something new I want to come back to the
the idea of the Proto Galaxy because
it's actually matches or you know
relates to to the black hole formation
so most large gal well pretty much all
large Galaxies have a supermassive black
hole in the center and we don't actually
know don't we don't really know where
they come from again we know that they
are there but how how do we get there so
if we go back to the to the early
Universe right we had a a little Galaxy
that just sort of you know I don't know
had some small number of stars it was a
first gravitationally bound structure
that that was held together by dark
matter because Dark Matter actually kind
of structured up you know first before
the Luminous matter could because that's
what Dark Matter kind of does and it it
started to hold
um gas and then Stars sort of together
in this first very shallow
um what we call potential well so these
gravitationally bound systems
and then the Milky Way Grew From
absorbing neighboring smaller even
smaller systems and somewhere in that
process
there must have been a seed for one of
these supermassive black holes and I'm
I'm not actually sure that it's clear
right now kind of what was there first
the Supermassive Black Hole uh or the
Galaxy so lots of people are trying to
study that and of course the black hole
wasn't as massive back then as it is
these days
um but it's that's a it's a big area of
research and the new um James Webb the
jwc the telescope the infrared telescope
in space is um is working on many people
are working on that
to to figure out exactly what what
happened and there are some some
surprising results
um that we really don't understand right
now so so to solve the uh the chicken or
the egg problem of uh do you need a
supermassive black hole to form a Galaxy
or does the Galaxy naturally create the
supermassive black girl yeah yeah I mean
I
we can't answer that because there are
lots of little dwarf galaxies out there
you know the Milky Way remains
surrounded by many
dozens of of small dwarf galaxies I have
studied a bunch of them and to the
extent that we can tell they do not
contain black holes
so they are certainly were
gravitationally bound structures so
either you can call them proto-galaxies
or dwarf galaxies or first galaxies they
were definitely there
but there must have been bigger things
like the Proto Mickey way where
something was different right what made
them more massive so that you know they
would gravitationally attract these
smaller systems to to integrate them
so we'll have to see how do we look into
that the into the the Dynamics of the
formation the evolution of the portal
galaxies is it possible that they shine
I mean what what are the
set of data that we can possibly look at
so we've got gravitational ways
which is really insane that we could
even detect this
um there's the light
what else can we uh so that that would
fall into the category of observational
cosmology and the the jwst is is the
prime telescope right now to any
promises big big steps forward this is
in its early days because it's only been
online like a year or so
um but that collects the infrared light
from the farthest
like literally Proto Galaxy's earliest
galaxies that light has traveled some 13
billion years to us and they are
observing these faint little blobs
um and folks are trying to you know
again study the early the onset of these
early supermassive black holes how they
shape Galaxy so they're they're seeing
that they are they were there you know
surrounded by already bigger galaxies
ideally I'd like for for my colleagues
to push a little bit further hopefully
that will eventually happen in terms of
looking towards the older and older ones
yeah yeah more and more sort of
primitive in terms of the structure but
of course as you can imagine if you make
your system smaller and smaller it
becomes dimmer and dimmer and it's
further and further that way so we're
reaching the end of the line from a
technical perspective pretty quickly but
it's dimmer and dimmer means older and
older
um
yes in a sense because it it all started
really small
or smaller yeah
in that phase of the universe it would
otherwise it it doesn't yeah uh just to
take a small attention about black holes
and
you know because you do quite a bit of
observational cosmology and maybe
experimental
um astrophysics
um
what's the difference to you between
theoretical physics and experimental so
there's a lot of really interesting
Explorations about
paradoxes around black holes and all
this kind of stuff above black holes
destroying information
do those worlds intermixed to you when
you especially when you step away from
your work and kind of think about the
mystery of it all
um well at first
adversely much crosstalk
personally I mostly observe Stars so I
don't usually actually think too much of
black holes about black holes and stars
is a fundamental kind of chemical
physical phenomena that doesn't that's
right the physics is kind of different
it's not extreme yeah um I mean you know
you could consider a nuclear fusion sort
of be perhaps extreme you need to tunnel
there's some interesting physics there
yeah but it's it's just a different
flavor and I don't I don't do these
kinds of calculations myself either
um
I I very much like to talk with my
theory colleagues about these things
though because I find there's always an
interesting intersection and
often it's it's just I've written a
number of um papers with colleagues who
do like simulations about galaxies and
so they're they're not quite as far
removed as let's say the the black hole
you know pen and paper folks but um even
in those cases we had the same interests
in the same topics but it was almost
like we're speaking two different
languages and we weren't even that far
removed you know both astronomers and
all
um and it was really interesting just to
take that time and really try to
to talk to each other
and it's it's amazing how
how hard that is
you know even amongst scientists we
already have trouble talking to each
other imagine how hard it is to talk to
non-scientists and other people to try
you know to
we're all interested in the same things
as humans at the end of the day right
but everyone has sort of a different
angle about it and different questions
and way of formulating things and
sometimes really takes a while to to
converge and to to get you know to the
common ground but if you take the time
it's so interesting to participate in
that process and it feels so good in the
end to say like yes we tackled this
together right we overcame our our
differences not not so much in opinion
but just in expressing ourselves about
this and how we go about solving a
problem and these were some of my most
successful papers and I certainly
enjoyed them the most it could also lead
to Big discoveries I mean there's a I
think you put it really well in saying
that we're all kind of studying the same
kind of mysteries and problems I mean I
see this in the space of artificial
intelligence you have a community maybe
it seems very far away artificial
intelligence and Neuroscience
you know you would think that they're
studying very different things but one
is trying to engineer intelligence
and in so doing try to understand
intelligence and the other is trying to
understand intelligence and cognition in
the human mind and they're just doing it
from a different set of data a different
set of backgrounds and the researchers
that do that kind of work and probably
the same is true in um
observational cosmology and simulation
so it's a it's a it's like a
fundamentally different approach to
understanding the universe
let me use for simulation let me use
the things I know to create a bunch of
parameters and create some
just play with it play with the universe
play God create create a bunch of
universes and see in a way that matches
experimental data as a as a fun it's
like playing Sims but at the cosmic
level yeah so but and then probably the
set of terminology used there is very
different and uh maybe you're allowed to
break the rules a little bit more let's
have you know yeah take the Drake
equation yeah you don't really know you
kind of come up with a bunch of values
here and there and and just see how it
evolves and from that kind of into it
the different possibilities the Dynamics
of the evolution of a galaxy for example
yeah but it's cool to play between those
two because we it seems like we
understand so little about our Cosmos so
it's good to play yes it's like a big
sandbox right and everyone kind of has
that little corner and they do things
but we're all in the same sandbox
together at the end of the day but in
that sandbox does have super powerful
and super expensive telescopes that
everybody's also all the children are
fighting for the resources to to make
sure they guess get to ask the right
questions using that uh big cool tool
well can we actually step back on the
the The Big Field of Stellar archeology
uh what is this process can you just
speak to it again you've been speaking
to it but what what is this process of
archeology in the cosmos yeah it's uh
it's it's really fascinating so
um I mentioned the the lesser the mass
of the star the longer it lives yes
yes and again for reference
um for the next dinner party the son's
lifetime is 10 billion years so if you
have a star that's 0.6 or 0.8 solar
masses then its lifetime is going to be
15 to 20 billion years
and that's that's an important range for
our conversation because even if you
assume that such a small star formed
soon after the big bang then it is still
observable today you mentioned old light
before yeah that light is like a few
thousand years old but compared to the
age of these stars is nothing
so to me that's Young
oh it comes straight from from our
galaxy or you know it's not far these
stars are not far away they're in our
galaxy
in the outskirts they probably did not
form in the galaxy
because again hierarchical assembly of a
Milky Way Bend exactly they're formed in
a little other galaxy in the vicinity
and at some point the Milky Way ate that
which means it absorbed all the stars
including you know these little old
stars that are now on the outskirts of
the Milky Way That I Used to point my
telescope to
so
what can we learn from these Stars why
should we study them now these little
stars are really really efficient
um with their energy consumption they
are still burning for the experts just
burning hydrogen to helium in their
cores and they have done so for the past
12 13 billion years however all they are
and they're going to keep doing that for
another few billion years same as the
sun the same Sun also just does hydrogen
helium burning and we'll continue that
for a while
which means the outer parts of the star
well pretty much actually most of the
star that gas
doesn't talk to the Core
so
whatever composition that that star has
you know in in its outer layers
is exactly the same as the gas
composition from which the star formed
which means it has perfectly preserved
that information from way back then all
the way to the day and going forward
so I'm a Stella archaeologist because I
don't dig in the dirt to find remnants
of past civilizations and and whatnot
I dig for the staff or the old stars in
the sky because they have preserved that
information from this first billion year
uh years
um in their in their outer Stellar
atmosphere which is what I'm observing
with telescopes so I'm getting the best
look at the chemical composition early
on
that you could possibly wish for what
kind of age are we talking about here or
talking about
something that's close to that you know
like a 13 billion 12 13 billion age
range that's what we what we think now
it has a small caveat here we can not
accurately date these tasks but we use a
trick to say oh these tests must have
formed as some of the earliest
generations of stars because we need to
talk about the chemical evolution of the
universe and the Milky Way for a second
so already mentioned the
uh the pristineness of of the universe
after the big bang right just hydrogen
and helium then the first stars formed
they produced a Sprinkle of heavier
elements up to iron than the next
generation of stars formed that included
again massive stars that they would
explode again but also the little ones
that keep on living right so and then
the massive ones again exploded
Supernova so they provide again another
sprinkle of heavier elements and so over
time all the elements in the periodic
table have been built up there have been
other processes for example neutron star
mergers and other exotic supernovae that
have provided elements heavier than iron
all the way up to uranium from Fair
early on we're still trying to figure
out those details but
I always say pretty much all the
elements were done from like day three
so iron is where like once you get to
iron you got all the fun you need
most of the fun
yes I know
uh I I really like the heavier elements
you know gold silver Platinum that kind
of stuff
for person reasons they're for Star
formation well both okay
I mean like what's the importance of
these heavier Metals in uh in the
evolution of the Stars
every Supernova gives you elements up to
iron that's cool but at some point it
gets a little bit boring because that
always works but that's the Baseline we
need that
um and that's certainly what came out of
the first stars and then all the other
Supernova explosions that you know
followed with every generation and it
took about a thousand Generations give
or take until the sun was made so the
sun formed from a gas cloud that was
enriched by roughly a thousand
generations of supernova explosions
and that's why the sun has its its
chemical the chemical composition that
it has including you know and somehow
the planets were were made from that as
well so the Supernova explosions the
many generations are creating more and
more complex
elements no it just goes all the way up
to iron yeah and then it's just it's a
little bit more of of all of these
elements just more yeah just yeah it's
one sprinkle then another and it just
kind of adds up right now the heavy
elements form in very different ways
they are not Fusion made they are made
typically through Neutron capture
processes but for that you need seed
nuclei
ideally you know iron or carbon or
something so the Supernova made elements
are a very good seed nuclear for other
processes that then create heavy
elements and because they cannot be made
everywhere they when you when you know
so I my sum of my stars have huge
amounts of these heavy elements in them
and they tell us
in much more detail
something really interesting happened
somewhere well wait I thought I thought
the really old ones we would not have so
what does that mean if if the old yes
important clarification
um so
the stars that we are observing today
these old ones they formed from the gas
and the question is what enriched that
gas ah so it could have been just a
first star dumping their elements into
that gas all the way up to iron
and we have found some stars that we
think are second generation Stars so
they form from gas enriched by just one
first star that's super cool yeah
then we find other old stars that have a
much more complicated
um heavy element signature and that
means okay they are probably formed in a
gas cloud
that had a few things going on
such as maybe a first star maybe another
more normal Supernova and maybe
some kind of special process like a
neutron star merger that would make
heavy elements
and so they created a local chemical
signature from which the Next Generation
star then formed
and that is what we're observing today
so all these old Stars basically carry
the signature from all their this these
progenitor events
and it's it's our job then to unravel
okay which processes and which events
and how many you know may have occurred
in the early universe that led to
exactly that signature that we observed
13 billion years later is it possible to
figure out like the number of
generations that resulted in this
um in these Stars well we can we we
think we can sort of say okay this was
like second generation or third because
the amounts of heavy elements in in the
cells that we observe
um is so tiny one Super One normal
Supernova explosion is actually already
basically too much it would give us too
much of it and the thing is you can
never take away things in the universe
you can only add there's no Cosmic
vacuum cleaner going around sucking
things away
the black holes are probably the closest
to that but they would have taken the
whole stop yeah they'd take the whole
thing not just they wouldn't take up
stuff out of the gas you know
um so we have a
maybe 10 stars or so now where we where
we are saying they're contained so
little of these heavy elements that
there must be second generation because
how else would you have made them and
again I wanna I wanna stress that the
elements that we observe in these stars
were not made by the Stars themselves
that we observe they that's just a
reflection of the gas cloud so we don't
actually I had to say that because I
love Stars we don't at the end of the
day we don't really care for the stars
that we're observing we care for the
story that they're telling us about the
early universe so yeah so the stars are
kind of a small mirror yeah into the the
the earlier yes yeah
and so what are you detecting about
those thoughts can you tell me about the
process of archeology here like what
kind of data can we possibly get to tell
the story about
um these heavy elements on the Stars
that depends really on
um what store you find
um there are many different chemical
signatures
um we actually pair up these days our
our
um our element signatures with also
kinematic information how the star moves
about the Galaxy that actually gives us
Clues
um as to where the star might have come
from because again all these old stars
in the galaxy but they are not off the
Galaxy that's a small but important
distinction so they all came from
somewhere else so you can rewind back in
time to kind of estimate where it came
from yeah so we can't really say oh it
came from that and that dwarf Galaxy but
interestingly enough so I'm just I just
a few days ago I submitted a paper with
three women undergrads it was so good to
work together and we found a sample of
stars that have very very low abundances
in strontium and barium so very heavy
elements
and I had a hunch for a while that these
Stars would probably be some of the
oldest because
as I said heavy elements give you extra
information about special events
and again finding something that's
really low
means it must have for it that must have
happened either really early on or in a
very special environment right because
we can only ever add so if you find
something that's that's incredibly low
in terms of the abundance it
maybe just one event contributed that
Max
so
we looked at the kinematics how are
these Stars moving and they're all going
the wrong way in the galaxy
how how is that possible well it is
possible because consider now we come
back to the Proto Galaxy the Proto
Galaxy was like a beehive it just didn't
really know what it was or what it
wanted to become when I grew up
so and it was absorbing all these little
galaxies to grow fast
some galaxies some absorbed galaxies
were thrown in going the main way and
some came in the wrong way huh happens
it happens but this could only happen
early on when you know there wasn't left
and right and up and down
so stuff would come in from always so
now
13 billion years later we're still doing
it yeah the a they're still doing it and
B we just looked for stars that have low
straw human barium abundances and then
we look at the kinematics and lo and
behold they are at hundreds of
kilometers per second going the wrong
way it's like dude you must have come in
really early on from somewhere else so
we call this retrograde motion that's a
clear sign of accretion so something
that has come in to the Galaxy and
because they are so fast
um and it's really all of them that that
must have happened early on right you
can't throw a Galaxy into the Mickey
right now the wrong way it eventually
will turn around can you actually just a
small tangent speak to the the three
women undergrads like this little it's
pretty cool that you were able to
um
use a hunch to find this really cool
little star
um yeah what's the process of like
especially with undergrads I think that
would be very interesting and inspiring
to people yes it was a wonderful little
collaboration that actually emerged in
the fall
um I
so I like I really like working with
with undergrads and grad students
postdocs
um and I came up with a New Concept for
a class at MIT where I wanted to
integrate the research process into the
classroom because sometimes
um people find it really hard to called
email a professor hey you know this is
I'm this and that person and I'm
interested in your research could I
possibly you know come yes and um I
wanted to to streamline that and give uh
and you know just trial how it would
work to provide a sort of a safe
confines of a classroom where you just
sign up and do research in a very
structured way
and uh I developed it was a lot of work
a little bit more than I thought to map
up an entire research project basically
from scratch in 10 worksheets so that
they could do it again in a very
structured and organized fashion created
this whole framework for it for them to
do the whole thing
um but the promise was
you come sign up for my class in teams
of two you each get your own old star
that has not been analyzed before I
don't know what the solution is because
in research we don't look up the
solution at the end of the book we do
not know what we're going to find our
job is to do the work and then to
interpret the numbers because our job as
scientist is
to find the story anyone can crunch
numbers
anyone
it's it defines complicated sometimes
but it's doable right yes but coming up
with a story when you only have three
puzzle pieces what does the puzzle look
like
that you have to be a little bit bold
you need to have some experience
and you need to you need to kind of see
the universe in 3D you just need to kind
of go for it and that's the beautiful
thing I really love that and so this was
a story of weird kinematics going the
wrong way combined with this particular
weird signature in terms of the elements
exactly and you have to come up with a
story yeah and so the story of that
paper is now usually I don't say I find
the older stars you know when I talk to
my research colleagues I I talk to them
about we find the chemically most
pristine stars because that's actually
what we measure the chemical abundance
that tells us okay it must have been
second or third or fifth generation of
stars right but these low strong theme
stars that go in the wrong way like
they're getting paid for it they must be
the oldest stars that came into the
Galaxy because they formed before the
Galaxy
was the Mickey way right and this is so
cool and it was so wonderful so this
class it it went so well in the fall I
had nine people sign up that's not
unusual for for classic specialty class
at MIT so small number it was eight
women and they were so into it that I
said okay
let's use this opportunity you're gonna
do some extra work with me
and we're going to publish this try to
publish yes I also like that
um you're using the terminology of
chemically more pristine when I'm
talking to younger people I'll just say
that I'm more chemically pristine than
them I like the description of age so
there's this term of metal poor Stars so
most of these old stars are going to be
metal poor yes I I search for the most
metal poor stars and what does that can
we just Define yeah
I don't know who came up with this I
would I would love to know but um
the universe is a complicated place so
many decades ago someone clever came up
with the idea to say
let's simplify things a little bit let's
call hydrogen X helium Y and all the
other elements combine Metals Z
[Laughter]
when I give public talks I always ask us
is there a chemist in the audience
let me just tell you neon is a wonderful
metal and they're like oh my God what's
he saying but I'm an astronomer I'm I'm
not a chemistor I'll get away with it so
if you just roll with it for a moment
all the elements except hydrogen helium
are called metals
now if we look again at chemical or the
concept of chemical Evolution it means
more and more of all the elements
everything heavier than hydrogen helium
gets produced slowly but surely by
different types of stores and events
so that's a you know a monotonously
increasing function
um and so we look for the stars that
have the least amounts of heavy elements
in them
because that means we are going further
and further back in this process in that
function
almost all the way to the very beginning
and that is the first Stars right they
they started that that process that's
why I said it was such an important
transition phase because it things were
we we call you know the the post big
bang universe pristine just hydrant
helium and after that the mess started
if you soon as you add elements to it
things kind of get a little out of hand
that that's that ends in this beautiful
variety that that we have everywhere
these days yeah and you're looking at
the very early days in the introduction
of the variety yes exactly when it was
still a little bit more organizable
um but the the variety of different
types of metal poor stores we have a
stark
um many different types of stars many
patterns we have sort of identified but
they are so crazy ones out there that
we're still trying to kind of fit in
so what kind of stars have been
discovered so you've uh already a while
ago uh helped discover the star he
1 3 27 23 26 great name yes and I Chief
15230901 what can you say about these
these stars and others that have been
found I love them okay they're my baby
Stars what do you call what do you call
what do you call your your baby Stars
well I'm probably the only one who can
you know spit out these names without
cheating there's nicknames are there
well no that's that's that's not allowed
okay uh well some colleagues at
conferences have just called them anasta
or Freebo staff because they they didn't
want to learn the the phone number you
know I I get it phone number yeah and
these numbers are actually based on on
older sets of coordinates for these
Stars so they um yes the the minus in
the middle means that they're in the
southern hemisphere so negative is in
the southern hemisphere positive
and then uh 13 and 15 means that sort of
observable in the middle of the Year
okay so that's the deal with the
observation and where it was observed
yes yes but um have very different
stores both absolutely significant
career defining actually for for me but
really pushed pushed the envelope in in
very different ways so 80 1327 of the
first one that you mentioned that was
the second second generation star that
we found and you know usually people say
like oh the first one is the big one and
the rest is nobody cares but to us it
proved that yes we can do it because one
astronomers live in a sort of way of you
know there are a lot of serendipitous
discoveries and we
that's really great but we need to show
that we can do it again reliably because
then then we're on to something it's not
just some kind of weird Quirk and there
are a lot of quirks in the universe but
we want to know is is that a real thing
does that happen regularly is there
something that we can learn right is
that a piece of the story
and so finding the second one that was
even a little bit more extreme than the
first one really showed yes our search
techniques work we can find these Stars
they provide an important part to the
story
in the sense that
if we had more than two stars and by now
we have about 10-ish or so
what do they tell us about the nature of
the very first Stars
and what we found
um again working with a theorists of
course who run these Supernova models
is that so actually let me let me before
I get into this these two stars had huge
amounts of carbon relative to iron so we
usually use iron as a reference element
for what we call the metallicity so the
overall metal content the overall amount
of heavy elements in it so that's why
it's called iron deficiency that's right
so this does an incredibly iron
deficient which means there must be of
the second generation because
there was and interestingly enough
there was this discrepancy
a normal Supernova until then we thought
would get us so much iron
you know you would distribute that in
the gas cloud and then you would form
this little star that we're observing
but the iron abundance that we measured
was actually much lower than that and I
already mentioned you can't take things
away that must mean these early massive
pop three we call them population three
the first Stars
they must have exploded in a different
way than we previously thought they
can't output as much iron because
they just can't otherwise it wouldn't
match our observations got it and so
that's when we started to work with uh
several Theory groups
on on supernova yields so what comes out
of from the explosion of the Supernova
that's called Supernova yields and so
this one was not yielding much iron well
we needed to concoct a theoretical
Supernova that made less
and it's actually surprisingly difficult
because you can always add more in the
universe right but you can't take stuff
away so Japanese colleagues kind of came
up with the idea of a fainter Supernova
that just doesn't have a much is enough
oomph you know when it explodes so
somehow there's there's less iron coming
out but at the same time then these
Stars showed huge over bonuses of carbon
you know a thousand times more carbon
so how do you now get a thousand times
more carbon out of these poor first
supernovia that was the theoretical
Challenge and because we didn't have
just one star but two
um that really spurred the field to
think about what was the nature of the
first Stars how did they explode what
what are the implications because if
they are not as as luminous and bright
and energetic that has consequences for
for these early proto-galaxies in in
which you know they must have been
located in terms of you know blowing the
gas out let's say and disrupting the
system so much higher chance for the the
earlier system to stay intact for longer
right so there's a whole tale of
consequences and this is what I mean
with we need to find the story because
you do you one thing and it's like The
Dominoes the consequences everywhere and
then you have a different Universe right
so what could possibly be a good
explanation for something that that
yields a lot of carbon and doesn't yield
a lot of iron
well it's not so much an explanation
more like finding a mechanism for what
happens in supernovae and the the
official term what what was sort of as I
said cooked up in order to to explain
the observations and we have by the way
found a whole bunch more of these tasks
so that holds and it's called a fallback
mechanism so actually in in the uh
Supernova during the Supernova explosion
a massive um black hole emerges and so
some of the material falls back onto the
black hole so here is a a vacuum cleaner
now plopped into the middle right like a
temporary one that just cleans up
somewhere sort of right because if you
think of the we haven't talked about
this yet but um if you if you know what
a star looks like a master star looks
like on its on its in its interior
before it explodes
um you have hydrogen helium still on the
outskirts and then you have your layers
of heavier and heavy elements all the
way up to iron so you have an iron core
in the center
um
and because you can't get any energy out
of iron when you want to fuse to iron
atoms anymore right that's when the
Supernova explodes what occurs really
it's actually an implosion first and
then you have a balance of of the the
sort of neutron star phase that that
that occurs in the process and then it's
so awesome gets disrupted yeah it's like
this giant you know basketball
it all goes up explosion first explosion
yeah and so in the process right if you
make your black hole basically big
enough it will suck away some of the
iron because that's the closest in the
in terms of the layers you you you hold
on to it you don't let it escape and
carbon is much further out you let it
all go
and so so that explains why you can have
a big oomph and not much iron yield yes
yes so is this explain the he 1327
correct uh and others like it yes so
there's a there's a
well well established now that the lower
the iron abundance of the stars are the
higher the carbon sort of gets and
carbon is is such an interesting element
in that regard
if if we come back to the formation of
the first Lomas does right so we had the
the hotter gas just hydrogen helium that
made the first stars there were 100
solar masses or so because it could the
gas couldn't cool enough so they were
big and puffy
carbon then coming from the first Stars
probably led to enough Cooling in these
gas clouds that enabled the formation of
the first lawmesters
so think about what happened if there
wouldn't have been any carbon or the
properties of the carbon atom would be
different it would not have cooled the
gas in such significant ways perhaps
there wouldn't be any lawmaster
we wouldn't be here today right and
we're carbon based and so I think carbon
is really the most important element in
the universe for for a variety of
reasons because it is just enabled this
whole Evolution that that we're now
observing and literally seeing in the
sky
and it's really fascinating so combined
with the fact that you have the iron
deficient so all of that is probably
important to creating
humans yeah yeah we need all the
elements but if you don't have stars you
know like the sun small stars that can
actually host planets that have long
lifetimes you need long long lifetimes
if you want to have a stable planet
and and develop humans and carbon is
kind of important in many ways yes yes
this is perhaps a
interesting tangent if I could just
mention that you interviewed a Mildred
dresselhaus carbon Queen
the remarkable life of the Nano size
Pioneer
um is there something you could say
about the magic of carbon and the magic
of Millie
well Millie was certainly magic
she was a professor at MIT for many
decades I I met her a number of times
her photograph actually a young and an
older Millie is still on the wall every
time I step out of the elevator in one
of the buildings I see it
um she pioneered all sorts of carbon
um Nano work so she is a was a material
scientist
um very far removed from what I do on a
daily basis
um but yes carbon has amazing properties
when you study it and again that's
indeed another aspect of why carbon is
so fascinating
um not just in in the cosmos but also
for us you know making us creating us um
in the way that we can use it
um it's wonderful you sometimes think
about this chemical evolution
in this big philosophical way that we're
we're the results of that chemical
Evolution like we're made of this stuff
like we're made of carbon yes we're made
of sore stuff yeah and it can go right I
mean it's almost like a cliche statement
but it's uh it's also uh a materials a
chemical a physics statement so it came
from hydrogen and helium
and somehow this formation has created
these this interesting complexity of
soup that made us
what are we supposed to make of that
like what did we just get really lucky
why why do we get all this cool stuff
yeah that's that's a good question I
don't think it's a question as an answer
I keep just asking why no but it's uh
it's just this incredible mystery so
much cool stuff had to happen
so much sorry Hot Stuff had to happen
right and and so much could have gone
wrong and there would have been another
outcome you know and it's actually
amazing how how many things kind of fell
in place I mean maybe that's all sort of
self-deterministic in some ways right we
are who we are because that that was the
path maybe we would have ended up being
robots I don't know
um but it's it's it's certainly
wonderful to
you know a scientists for us to to help
contribute unraveling our our Cosmic
history right I always say the
biological evolution on Earth was
you know absolutely facilitated by the
chemical evolution of the universe right
and one doesn't go without the other in
that Evolution from a human perspective
that Evolution seems to be creating more
and more complexity the kind of
interesting clumping of cool stuff
seems to be accelerating and increasing
it it's hard not to see as humans that
there's some kind of purpose to it like
a momentum towards complexity and Beauty
you know
well Beauty's in the eye of the beholder
but yes everything gets more complicated
but there's also a beauty to the the
chemically pristine Universe in the
early days
yes yes I love the desert it's
nothingness yeah that it has so much
Aesthetics and appeal we came from
nothing will return to nothing so what
about he 1523
what's exciting a red a red giant star
yes
uh that's another one of your babies yes
13.2 billion years old
um yeah um so that one isn't quite as
iron deficient as the other one so
probably not a second generation star
but easily second third sorry third
fourth fifth or so we we can't really
pin it down but that's also not super
important for us what what is important
is that that star has a very different
chemical composition in a sense that yes
we have all the elements up to iron
there
they have sort of normal
ratios uh which means kind of the same
as most other old stars and not too
different from the Sun or at least you
know different in quantifiable ways
um but it has this huge overload of very
heavy elements
and what was so nice about that stone
particular was that I could measure the
thorium and the uranium abundance
and again that was the second of its
kind
um but the uranium abundance was could
be more well determined so we had a
better grasp on that now why arthurium
and uranium interesting
um they are radioactive elements they
have they Decay thorium has a half-life
of 14 billion years I believe and
uranium of 4.7
which uh you know to focus on us on
Earth is a really long time but those
kind of timelines are really good when
you want to explore the early universe
so
there are two questions now that that
kind of come to mind
where do these elements come from and
what what do they tell us right and um
these as we know
these heavy elements are made in a
specific process it's a neutron capture
process usually referred to as the r
process for Rapid Neutron capture
process we talked about seed nuclei
before right so we still don't exactly
know where this process can occur so you
have let's say a lone iron atom
somewhere and it it is in an environment
where you have a strong Neutron flux
which means there must be lots of
neutrons around and again when we talk
about the side we can summarize and
Ponder where where that might be the
case
um but you have this iron atom and you
bombard it with neutrons and you do it
incredibly fast now what happens in the
process that iron atom you know you
collect lots of neutrons it becomes
really big and unstable so it's a heavy
Neutron Rich nucleus
that wants to Decay
because it's not stable it's way too big
um and so let's say you add only one
Neutron to it that would already make it
unstable so it will then it has a
characteristic Decay time that's called
the beta Decay time scale so it will
Decay to a stable nucleus so the neutron
will convert to a proton and that makes
it stable
if you know bombard lots and lots and
lots of neutrons onto that seed nucleus
within that time scale of the beta Decay
that's how you get to this huge fat
Neutron Rich nucleus that then wants to
Decay right so the r the rapid process
is you have your seed nuclear they get
bombarded you create these these really
heavy Neutron Rich nuclei
they are heavier than uranium even
the neutron flux stops and then all
these heavy nuclei they Decay and they
make all these stable isotopes that we
know of all the way up to thorum and
uranium
so that rapid nuclei Decay is what
creates all the functions correct and
the whole thing is done within two
seconds
so just to add to the rapid here
and literally the snapping on my hand
it's it's all there in my talks I often
I have this nice simulation that that
illustrates
um you know this this creation of these
rap of these heavy neutral nuclei and I
always say this is the only simulation
you will ever see that's slower than
real time
because in astronomy you know we show oh
this is how Galaxy forms 13 billion
years in 30 seconds
really short right this is the opposite
me showing you this the element is
already long long made so where and when
does this happen does this process so
you need the strong Neutron flux
the clumping of the the neutrons yes
that's right and so there are not that
many options right so where do you find
lots of neutrons in the universe so it's
neutron stars right neutron stars form
in the making of supernovae of the
explosions
okay so maybe some of this heavy
material gets sort of made in the making
of the Supernova explosion and then gets
expelled
or you have neutron stars so the you
know if the neutron star survive I mean
usually that's the leftover of the
Supernova if you have two from a binary
pair so Stars usually actually show up
in pairs and so it's not too unusual to
um create a pair of of neutron stars
that will still orbit each other after
both of their progenitor Styles have
exploded
and those two Neutron cells will orbit
each other diligently but as we know now
thanks to ligo the gravitational wave
Observatory
ah I mean we know already that
before but now it's been measured by
ligo is that these two neutron stars
they will orbit each other for like
forever but in the process they will
they will lose energy so that that orbit
is what we call the orbit decays and
eventually the two Neutron cells will
merge and that results in a in an
explosive event that has roughly the
energy of a supernova but uh the process
is completely different and the cool
thing is when these two neutron stars
collide they produce a gravitational
wave signature because neutron stars are
super dense objects they are like giant
atomic nucleuses so there's a lot of
interesting physics happening already
and so if you basically form a super
neutron star by Smashing two into each
other
uh more interesting physics happens and
that means that there's this Ripple sent
out you know into the space uh the you
know the space-time Continuum basically
you know the what do people say the the
ripples of space time you know it's like
yes it's like you drop a rock into water
right you see the waves coming so that's
exactly what happens when two two
neutron stars emerge and this is
Neutron's Galore right it's really
violent to smash two neutron stars you
know so that are so dense already into
each other
and um they in in 2017 one of these
events occurred and the ligo and Virgo
gravitational wave observatories they
detected that and then the astronomers
pointed their telescopes in that
direction and they indeed observed what
we call the electromagnetic counterpart
so there was something seen in the sky
that faded over the course of two weeks
and that's light curve that light was
exactly
what you get when you create all these
heavy Neutron Rich nuclei in the r
process and then the neutron flux stops
and then it takes about two or three
weeks for most of them of these nuclear
2 DK2 stability
so we saw the astronomer saw in this
electromagnetic counterpart
the nucleosynthesis of heavy elements
occurring
and that's that's just that's amazing
awesome so that's so awesome that's
electromagnetic counterpart to the
gravitational waves that were detected
with yes two neutron stars colliding
aggressively violently to create a super
neutron star and that's where you get
all the neutrons and neutron flux
somehow and then that the whole shebang
that happens in two seconds so that
confirmed that one of the sites for sure
is
for the r process to occur as neutron
star mergers interestingly enough I have
to mention this here A year prior in
my former graduate student Alex G and I
we discovered a small dwarf Galaxy
that is currently orbiting the Milky Way
it's called reticulum 2 that was full of
ancient iron deficient stars that also
had a strong signature of these heavy
elements exactly like he1523
we weren't looking for that I actually
wanted to prove that they had really low
levels of heavy elements because that's
what we had seen in all the other dwarf
galaxies
and I was dead set on showing yet that
that is yet the case again and that that
is a typical signature of early star
formation we already talked about low
strontium and barium abundances and the
oldest Stars right this is what we had
seen anecdotally in in the ancient dwarf
galaxies that are surrounding us so
that's an ancient dwarf Galaxy the
network galaxy has a bunch of ancient
stars in it yes
and so now we find reticulum 2 and it
has these the Stars show the signature
of the rapid Neutron capture process the
r process and we elect
okay these stars are located in a dwarf
Galaxy right now we have environmental
information they are not lost in the
Galaxy where we don't know where they
actually came from now we know these
stars were formed in that Galaxy because
they're still in it
and that we already deduced from that
that it must have been a neutron star
merger that went off in reticulum 2 at
Early times that polluted the gas from
which all our little stars formed can
you speak to what a dwarf Galaxy is can
you speak to what this particular two
dwarf Galaxy is that it's orbiting the
Milky Way galaxy yeah it's going to be
eaten by it presumably it totally is
going to be eaten I can't tell you
exactly when
um yeah the Milky Way remains surrounded
by dozens of small dwarf galaxies and
they are collections of stars
um some of them we call them Ultra faint
dwarf galaxies because they now only
contain I don't know a few thousand
stars
um very very faint still detectable uh
yes because they're fairly close and and
we detect actual individual stars now so
I've observed some of the the faintest
Stars you know you possibly observed
with current telescopes in in these
dwarf galaxies because I was like I need
to know what the chemical composition is
because there are leftovers from the
early Universe right they they did not
get eaten so they're still in their
native surroundings I I go it's like
getting the lions in the wild right I
gotta study those and compare to the
counterparts that got eaten and are now
in the Milky Way and so I so presumably
most of those Stars it's not all those
Stars Network Galaxy are really ancient
they're all really ancient because
actually as it turns out if you have a
small Galaxy
um
there was a process early on in the
universe called reionization that kind
of heated up everything and together
with some Supernova explosions in an
early shallow you know bound system
all these little systems lost the gas it
was sort of blown out or it simply
evaporated or both probably both
um and so these systems have been unable
to continue to form Stars since so it's
it's it's the best
for a Stella archaeologists that you
could hope for because it's a whole
bunch of stars still sitting there it's
not just one there's a whole bunch of
them still sitting there ever since and
nothing has literally nothing has
happened to them they're just been
waiting there for us so from the Stellar
archeology perspective what is like
juicier more interesting the uh
the old stars and the outskirts that
have been eaten or the outskirts of
Milky Way or the the stars in the in the
dwarf galaxies what's uh what's uh about
the world you said you love Stars so uh
which do you love more of you oh that's
a hard one I mean I love them all of
course
um they serve different purposes the the
SAS in the Milky Way um I can get much
much better data for them because
they're brighter they're closer so
they're brighter and that uh that
tickles my fancy and they have
interesting kinematics presumably yes
and we can get that and so he1523 for
example you know that one is really
bright only it's a red giant so it's
intrinsically bright and it's fairly
close
and so the data I got for that was
insanely good and that yielded this
uranium detection and thorium detection
um I can never get that kind of data for
dwarf Galaxy Star so that's a big
trade-off but the environmental
information that would we get along with
the basic information about these stars
in each dwarf Galaxy is really really
valuable in establishing you know these
um for example these site information
right sure because the the Galaxy is
still there so nothing crazy could have
happened so actually to close that Loop
probably some heavy elements come out of
supernovae here and there but somehow my
theory colleagues tell me that the
normal Supernova just doesn't have
enough oomph to really get an R process
going and doing doing it all so any
disorbiting super
we need them the probably the neutron
star mergers or we need a special kind
of supernova that's maybe extremely
massive or heavily rotating or does
something else funny right to really
kind of get that particular process
going but uh the normal supernovae don't
do it right so only a little bit comes
up but you could come alongside Anna why
don't you just take 100 supernovae
together to build up the yield right but
then I come along and say like Mike look
this dwarf Galaxy is still intact today
if you would have plugged in 100
supernovae into this little system early
on it would have blown apart it would
have blown apart past five supernovia or
ten so that's a really important
constraint that we have that these
systems are still alive right so
um it helps us to pin down where certain
processes could have possibly happened
and so that's it's just a it's just a
different type of information that we
get
it'd be amazing if we could talk about
the observational aspect of this the
tools of observation so what telescopes
have you used do you use and what does
the data look like and I think I've read
a few interesting stories about the
actual process of day-to-day observation
a bunch of uh probably late nights
well yeah astronomers are doing it all
night long so oh yeah
can you explain the all night long
aspect of it
um well let me start by saying uh I
mostly these days use the Magellan
telescopes in Chile they are 6.5 meter
telescope which means the the mirror
diameter is 6.5 meter
um that's not the largest that there's
out there but it's among the largest and
um I use a spectrograph because I'm a
spectroscopist I don't take pictures
um and uh that particular spectrograph
at that telescope is actually
um unusually efficient so it kind of
makes up for the fact that the mirror
isn't as large and not let's say the
eight meter telescopes from the
Europeans or so so I'm very happy with
that efficiency meaning how many photons
get collected sort of per time unit
because we that that's always the
limiting factor
um
uh prior to the pandemic we would travel
to Chile to do our observations
um those telescopes are the that's the
last Observatory where people were sort
of supposed to travel there and take
their own observations most other
observatories
basically have staff there by now who
take the observations for you
so there's the directly the scientists
are
specifying where to point the telescope
and sitting there and collecting the
data make sure the data is collected
well the cleaning of the data the what
offloading of the data all that kind of
stuff yeah so it's mostly done for them
yeah
um obviously that's super convenient but
it also takes takes away a central part
of what the work of an astronomer is
which is data collection
right we don't have an experiment in the
basement where we can go day and night
or whenever we please
um and ask a certain question of the
apparatus right let's
turn this knob and see what happens
let's turn that knob and see what
happens no you know we we only have one
experiment uh which is the universe and
we what we see is what we get
and I think it's it's so important to to
take an active role in that so I really
love going to the observatory I've taken
many students there over the years
to to teach them and to
just show them what it means to to be in
astronomer because you you go to the
these remote mountain tops and it's such
a magical environment and you wait there
you know for the sun to go down and then
you get ready and you look outside and
it's it's such a Serene environment
um it's it's a little bit out of this
world you're sitting there so the sun
goes down it's evening late evening
and uh what does it look like what are
some of the most magical experiences of
that process well you know when you're
on top of a mountain uh you know
climbers I guess get to see that
probably
um otherwise um
it's it's very calm and the colors are
so beautiful and
I always become much calmer when I'm
there I'm just a because I'm just there
for one purpose only that's data
collection
I can say no to my emails I can say no
to everything else because I'm observing
so there's literally less less
distractions because you know you're
just there to do one thing and also the
emails somehow seem less significant
yeah yeah it's just you can't afford to
focus on this one thing and you
it just kind of does something to you
it's it's a little hard to describe but
um
you know if you then fast forward maybe
I can speak a little bit about that and
I have done a lot of astrophotography
there as well so and and I observing
faint dwarf Galaxy Stars you know these
are like 45 minutes 55 minute exposure
so you actually have a lot of time so I
would run outside
and just lay on the ground under the
southern Milky Way
beautiful right up you know there and I
would just lay there like the snow angel
you know
and it just stare up there and just kind
of let my thoughts sort of pass through
my brain and just like I'm I'm one of it
right we talked about this in the
beginning this is when I personally have
the feeling that I'm a part of it I I
belong here rather than feeling kind of
small yes I'm small but there are many
other small things and lots of small
things make one big hole yeah we're part
of that big hole and um so that's
looking at the inner spirals yes Milky
Way galaxy and just you know this this
dark sky with the with the bright stars
and I have described this in my my book
um years ago
if the Milky Way Is All Bright above you
you don't need a moon or anything you
can walk in the Starlight and you will
find your way there are no trees there
for safety reasons but you wouldn't even
run into a tree right I mean you can see
you can almost see the shadow you know
from from The Starlight because it's
such a dark side and and the stars are
so bright and these are kind of moments
that that kind of change you a little
bit
and you see the unity of it all yeah and
it's just you and nature and
you know with modern civilization and
all of that we I think we often try a
little bit too hard to be removed from
from nature you know to to be
independent of it and figuring it all
out but at the end of the day we're just
a part of it and and that really helps
me to remember that that you know
well one and the same well that fills me
with hope that because I I tend to think
of us humans as in the very early days
of whatever the heck we are so that
makes me think uh thousands tens of
thousands hundreds of thousands of years
from now there will be reached whatever
we become will be traveling out there to
explore more and more and more yeah so
we're what you're doing is the early
days of Exploration with the tools we
have yes the early seafarers looking at
the sky for navigation coming up with
different theories of what uh what's on
the other side that the Earth is
starting to gain an intuition that the
Earth may be round
and then we might be able to navigate
all the way around to get to
um the financial benefits of getting
spices from India whatever the reason
whatever the grant funding process is
all about but ultimately actually
results in a deep understanding of the
mystery that's uh all around us and I
mean it's just to travel out there
I mean to me
the discovery of life in the solar
system
I really hope to see that in my lifetime
some kind of some kind of Life bacteria
something maybe dead because that means
there's life everywhere
and that that's just the kind of stuff
that might be out there
all the different
um
all the different environmental
conditions chemically speaking that are
out there and it just seems like when
you look at Earth life finds a way
to survive to thrive in whatever
conditions and so uh
maybe that process just kind of humbles
you as a super exciting to know that
there is life out there of different
forms and of course that raises the
question of um
what is life even we tend to have a very
human-centric perspective
of uh what is a living organism and what
is intelligence and all this kind of
stuff and all the work in artificial
intelligence now is starting to
challenge our ideas of what makes human
beings special
I think we're doing that through all
kinds of ways and I think you're working
some part doing that as well like the
unity you feel is realizing where uh
we're part of this big mechanism of
nature whatever that is that's creating
all kinds of cool stuff from The Humble
pristine Origins to uh to today
um
so what is if you could just kind of
Linger on the on the process of the data
what does the data look like and how
does the data the raw data lead to uh
a discovery of an ancient star
well as a spectroscopist we have to I
guess talk for for a brief moment about
what what a spectrum is yes
um
everyone I hope has seen a rainbow in
the sky that is
that is basically what we're doing uh we
don't send the Starlight through a
raindrop that then gets bounced around
and splits up the light into the rainbow
colors we
um we do it with a spectrograph so
basically a prism so we send a Starlight
through a prism of sorts and that splits
it up and then we record exactly that so
it's a little 2D picture actually of a
spectrum
now uh it's not gonna look colorful it's
just black or black and white different
and different colors have of course
different energies that's what what we
record
um more specifically we we record it as
as wavelengths so wavelengths and
frequency and energies all all the same
at the end of the day
um we process that that little image in
the sense that we do a cross cut
and then sum up a few columns so that we
get all the data that we recorded and
what we see is a um it's a bit funny to
describe just with words but a wiggly
line with lots of dips so the 2D process
Spectrum we call it Continuum so it's
just a flat line basically and then they
are dips so the interesting things are
the dips if you think back of the
rainbow what we actually see in Our
Stars is not just a rainbow but it would
be a rainbow with lots of black lines in
it which means certain little pieces of
color have been eaten Away by a certain
amount and so we can no longer see it as
well or not at all
why is that happening so if we come back
to our Stars what we're observing we're
observing the Stella surface we can
actually never peer without telescopes
inside we only ever go can go after the
surface
and the
surface contains oh the surface layer
contains different kinds of elements
every one of those types of atoms so
elements are just different types of
atoms they absorb different photons that
are coming from the hot core where the
fusion is occurring and so that means
that if you're the Observer you know
with a spectrograph or without
um you will see the Starlight but
certain frequencies certain energies of
that light will have been absorbed by
all the different atoms in the gas
so you see less of them and so those are
the dips and the strength of the dips
tell us you know which element was it
and how much of that element was or is
in in the star
so we have many many dips the the solar
Spectrum for reference you know all the
dips are overlapping because the
abundance of all the elements are so
high it's actually very complicated
Spectrum my Spectra really look like a
straight line and then there's a dip
here and then you have the straight line
again there's a dip there the sun
doesn't have straight lines I mean
that's just all absorbed in some form or
another
um but the old stars have so little of
all the elements that they're only
occasionally these dips that then
indicate okay that one at that
wavelength was iron and here we have
carbon and there's magnesium and sodium
and oh there's a little strontium line
here so we have a much easier way to
um map out this barcode that the
Spectrum you know pretty much is in at
the end of the day and to then measure
the strength of these we call it
absorption lines to then calculate with
existing codes that mimic the physics of
the Stellar hemispheres like how much
was absorbed how many what what kind of
elements were were present in in the
cellar atmosphere
and so this is how we get to our
abundance measurements and then all
together that gives us the the chemical
composition and and that particular
signature in that star
if you uh do you ever look at like the
raw spectrograph and the absorption line
and they're able to see
Intuit some interesting non-standard
outlier kind of patterns
or does this have to do heavy amount of
processing
um we actually process our it's fairly
straightforward to to do our processing
we do it at the telescope so I often
take a shorter exposure first let's say
10 or 15 minutes uh so mostly when I do
Discovery work we would just take a
quick look Spectrum then we process it
while we observe the next uh
then we take a quick look we have what I
call the summary plot it's it's a
collection of little areas in the
spectrum that have the the key positions
uh the positions of the key elements in
it and it's kind of like reading the tea
leaves I have stared at so many Spectra
I just need to know I just need to see
our summary plot and I can tell you
exactly what the numbers are going to be
awesome and also to tell if it's going
to be promising to look at further
exactly and so that's a thumbs up thumbs
down
uh you're worth my time
or not in most cases it's not or it's
good enough we can do a basic analysis
maybe publish this as part of a larger
sample just so you know we output that
we have observed the star and and their
basic nature that that's an important
part to to publish as well
um and uh yeah I had a I had a run so
now we do remote observing I do all of
this now from my home from my living
room all night long
um and
um I often work with with colleagues so
we we do it over zoom and we process the
data we look at it same thing still and
we we just found a star that
um had a very low iron abundance and
then we decided okay that looks
interesting we're just gonna keep
exposing so we'll talk more data on it
on the spot and we're writing up the
paper right now how do you know where to
point the telescope it's not random
there's a lot of work that goes into
that
um I began my career by
answering trying to answer that question
as in like doing the search process
that's why I called my my book that I've
written some time ago searching for the
oldest ass because
searching is one thing it's very time
consuming and then on top of that not
everyone finds right and I often don't
find but I keep searching because you
know techniques have established that
yes we can do it if we're just patient
enough and keep going because it's a
numbers game and that's often the case
in science and that's something that not
a not enough is talked about how tedious
it is and how long it takes to get to
that one
a discovery right that that moves the
field further and how difficult it is to
believe that there is a thing to be
discovered yes yes
um if we have the saying I I learned
this I think from my supervisor one star
is a discovery
two is a is a sample and three is a
population so as soon as you found three
of roughly the same kind you're done but
you need to get there yeah probably at
first is the hardest right yes but it
kind of remains really hard and but the
thing is that at past three many of us
are okay we solved that problem
we've done it three times so we can't do
it that's a thing right that's a
population three iron deficient Stars
let's say right that's one puzzle piece
now we can move on to the next thing
that's an indicator that there's many
more of them yes potentially yes yes yes
so to cut a long story short about the
searching
um we started early on with
um what's called low resolution
spectroscopy of many stars so for
example my thesis work almost 20 years
ago was piggybacking off
um a quasa survey that had collected so
quasars are basically giant supermassive
black holes that are really far away so
you only see a one big bright light
point so it looks like a star but it's
actually just a giant supermassive like
all that outshines it's it's its own
Galaxy
and people had been trying to study
those and they had taken little Spectra
of of you know all things in the sky and
it turns out oh you can fish out the
actual stars from that and and look for
certain signatures
um that might indicate uh Low Middle
City Star so it starts with low
abundances
um and so it was painstaking work to
then take medium resolution spectroscopy
to get a little bit more information and
to use the approximations and to kind of
get candidates that we can then
eventually take to the big class like
Magellan to get a high resolution
Spectrum so we really see the dips of
all the individual elements that then
give us the final answer is it yay
already
um these days uh with another grad
student I just I developed a new
technique to use
um images actually of all the stars in
the sky taken with very narrow filters
so it's like you're wearing very
specific glasses that only let so much
light through and so we can do similar
things
through having several narrow band
filters what we call it to fish out
things that have you know no absorption
over here so just the the straight line
and then a little dip here so a little
something there
and that has proven fairly successful in
recent years so looking at the entire
looking at a broader regions of space
that's right because these stars are a
little bit like the needle in the
haystack right there are not that many
left over and the certainly the galaxy
has made plenty of stars in between we
need to comb through all of those
um to to get to the goods yeah so we
always start with millions and then work
our way down and in the end we have like
three good candidates I wonder how those
ancient Stars feel that they were
noticed they probably know that nobody
pays attention
no I'm just kidding we're all special
right so understands it's good it's
inspiring even if you're the outcast
um in your pristine nature you still
might nevertheless be noticed I'm hoping
the same about humans if somebody's
observing us
um
is there something else you could say
that's
about the challenges of this kind of
high Precision measurement
uh that you're doing
so this kind of collection of data
looking
trying to come
pull out the signal from the noise out
there
well that's literally what we're doing
in multiple ways actually so we find
trying to find the needle in the
haystack
and then we find something and then it
turns out
it's just a little bit too faint to
actually get the kind of data quality on
it that we would like or that would
would be warranted given the the
potential of the Star right it's like so
there's always noise
there's always a little bit of noise and
you have to try to say like what uh yeah
how special is this when you're looking
at the absorption line yeah how so the
most iron Pro Stars their iron lines are
so tiny that they're literally you know
almost in the noise so you need an
incredibly good data to make detections
and and the funny thing is we're looking
for the nothingness of let's say the
iron lines but then we don't want
nothing because if there's nothing in
the Spectrum we can't measure anything
we can only get an upper limit but we'd
really like a measurement so we are
looking for the the last little bit that
you could possibly detect and that's the
strong function of the brightness of the
star because the telescopes have the
size that they do that that's not going
to change for a while hopefully
eventually it will but it's going to be
at least 10 years out
um and so yes we'll often literally
stuck in the noise because we can't make
the measurement so actually the record
holder for the most iron poster only has
an upper limit we can't get enough data
on this to actually pinpoint a
measurement to then take it to our
Theory colleagues and say like give me
this little iron out of your first star
so it's a bit frustrating but also super
exciting at the same time so let's go to
both sides of that Spectrum what's uh
what's like the most exciting Discovery
to you personally where it's is there a
moment you remember that you saw a piece
of data and you kind of your heart
skipped a bit
um yeah yeah of course is it the is it
uh he1327 that was that was definitely
one of those moments I wasn't actually
present at the telescope but we will
send the data immediately for my
colleague
and we just looked at it and our eyes
got really white and it's like oh my God
this is this really what you think it is
so we had to run some numbers and and it
was and it these are magical little
moments yeah the thing is
you know often we we have false
positives yeah and so there's always
this this kind of period and often it's
it's I don't know 10 15 minutes where
you need to make some tests to kind of
make the decision is this really
something I should keep observing now is
this really as good as I think or or am
I being fooled by something right so
actually if you take a spectrum of a
white dwarf a white dwarf is the
leftover core of a star like the sun
that has gone extinct
and why dwarves have lost all their
outer atmosphere so it's just the
hydrogen helium core so they look like a
metal poor star because that's only
hydrogen helium left right but the
hydrogen lines that you can see in the
spectrum of our stars and of the white
dwarfs a little bit wider than normal so
you need to have a good eye just to
check you know does this look a little
bit wider than us is this a white dwarf
who's fooling me here right and so it's
like this moment it's like oh my God
it's just minutes of nervousness yes yes
and sometimes you know it's it's a dud
and sometimes it's not what's been uh
what's been a big that you remember
heartbreak like a painful low point
is it all leading up to the first is it
all about HG 1327 again just the leading
up to it or has there been like a
uh yeah has there been like low points
in this search
um that's a good question
I mean you know it starts with mundane
things as in like you you want your
telescope time you travel there
and the weather is completely cloudy it
rains and you you had three nights which
is a lot and you go home empty-handed
so that's definitely a low point
[Laughter]
uh probably not what you were thinking
of uh but there is a certain
occupational hazard to it which requires
a kind of
resilience and a patience yeah and you
just gotta learn to to live with it um
coming back to reticulum too actually
you know that little dwarf Galaxy that
was a run that we had and the weather
was incredibly bad and I had sent my
student there
um
and I was at home and he calls me at 2AM
and he was like Anna I think I observed
the wrong stuff I'm so sorry
there's this line there this europium
line and it looks like a metal Rich star
and I was like it's cool we all make
mistakes send me the data send me that
summary plot
and so I look at it you know I was like
super tired and it's like
I I can't really tell it doesn't look
wrong but I can't tell you right now
that it's right either so why don't you
go to the next Target
he calls me back an hour later you know
it looks just the same
what am I supposed to do
and then I joked well maybe we found an
R process Galaxy
let's go to the next one and the weather
was degrading
um and so to cut a long story short
we had to come so he was observing the
right stores it was an r-process Galaxy
the first one we had ever discovered
totally
and I mean unpredicted we had no idea
that this was a thing I mean you know
of course we we thought that you know
such a thing might possibly exist
because why not right Neutron summer
just happened somewhere uh crazy
supernovae probably too but we were not
prepared in that moment to to find this
thing
and
in the end the weather was getting worse
and worse and we wanted to see how many
our processors are in this galaxy so we
managed
by a hairline to observe the nine
brightest stars but the data quality was
atrocious and weather affects the data
quality yes absolutely because these
were really faint Stars
um so we we were really lucky by making
a very tight strategy of getting the
absolute bare minimum for all the stores
so we could at least take a a very crude
look is it a yay or is an a we couldn't
even say yes or no just just to get an
idea because we needed to know
why was that important because
we could only observe this system again
nine months later so there's always a
window of observation yes it was setting
this was our chance and it was going
away with the clouds you know
that was super high stakes but we we we
just made it like really it was
almost impossible and it was just the
the thing is this is such a
serendipitous moment in a serendipitous
moment the enhancement of these heavy
elements was so strong that even in this
really crappy data we could still see
the enhancement
right the absorption was so strong
they're stuck out of the noise if the
enhancement wouldn't have been as strong
we would not have been able to say
anything because we wouldn't have been
able to tell
but because it was so extreme it lent us
a hand despite the weather and all to
say like yes this is it
so that was quite the night
look that means a lot of this is just
luck
so that was the first our process Galaxy
discovered yes I didn't sleep all that
much
um do you have hope are you excited
about uh James Webb's Space Telescope
and other telescopes in the future that
uh increase the resolution and the
Precision of what can be detected out
there absolutely
um database is fantastic already I am
not planning to use it personally
although I think I'm on one or two
observing proposals actually because
similar to what we already spoke about
we're interested in the same thing we're
just kind of looking at the different
sides of the fence right I have my my
old surviving stars and I concoct these
little stories about what the earliest
galaxies may have looked like what what
the objects were that contributed you
know energy and and elements and all
these things and uh my jwst colleagues
they try to detect some of these
earliest photons from these earliest
systems to look at the energetics and
and other things you know what was there
how many these kind of things right so
together we're trying to to explore this
first billion years
but we do it in very complementary ways
and so I'm I'm very excited to to see
what what they can come up with and how
that helps me to inform my stories
better and more comprehensively
uh what do you think is the future
of the of the field of Stellar
archeology how much can we
maybe what are the limits of our our
understanding of this first billion
years of our uterus
um well obviously lots of limitations in
the sense that I always say I have a
metal poor star for any of your
questions
because there are so many different
kinds out there
um and we still find new patterns
sometimes right and there needs to be an
explanation the question is is it
ultimately just one quirky star or is it
two or is it three right is it is it a
sample is it a population so we haven't
concluded that kind of work yet so every
metal poor star
is the kind of data point that you can
use to improve the quality of your model
of how the evolution of the early
Universe yes yes and I would say we're
we've made huge progress over the last
20 years when I joined that field it was
in its infancy and there was this
serendipitous discovery of that first
second generation star
and we have filled in the canvas a great
deal since then and this is what I have
greatly enjoyed about doing so because
there was so much Discovery potential
and it's been it's been dying down a
little bit because of all the progress
um it's gonna it's gonna it's on on the
up and coming again because there's so
many large spectroscopic surveys in the
works now that will just provide a
different level of data that we haven't
had before I'm sort of of these older
generation I have only very few
colleagues I work in small teams and I
observe every single star myself
that you know I whatever I can I do
myself I don't generally take other
people's data at least not certainly not
in the end stage and and uh you know I'm
not a big data kind of person although
we're all headed that that way I I
certainly use uh data from the Gaia
astrometric satellite for the kinematics
for example but that's personally a new
thing for me to to use sort of Big Sky
surveys
um that are available
um so it's still very sort of hand grown
field you know where we do our
individual observations
um have enjoyed that a lot but that's
about to change so one star at a time
yes I mean there's power to that to
build up intuition of the early Universe
by looking one star at a time yeah and
and this is how you can really drill
down on the questions that you have
right because you control what data you
get
um otherwise you have the data that you
have right you get what you get and you
don't get upset
I don't like that I'm a little bit
snobby I I really like to formulate my
questions go to the telescope and then
come what may I will try to get it and I
also develop the intuition of where the
data can be relied upon and what it
can't and all the different quirks of
the data and all that kind of stuff yeah
sometimes a lot is lost
in the aggregation of the noisy data
yeah yeah yeah and and that's always the
danger if you have someone else's data
that you just don't really understand
the you know the limitations and
completeness things how certain things
were set up and you know you get out
what you put in so I'm I'm really
particular about that and it certainly
paid off for me that's one of the main
Notions that I try to teach in my
classes and to my my students that
you need to be able to formulate your
quest question really well because
otherwise you're going to get an answer
to a different question but you won't
notice that it had that the goal post
has shifted in the meantime right so
your interpretation can only be as good
as the question if you need to change
your question that's cool do it
but then you know it needs to pair up
with your interpretation again and so
knowing really being in the know about
every step of what happens that relates
to Quality results I think that's why I
have sometimes a little trouble with
with sort of big data and statistical
analysis yes on average that's true I'm
not debating that but I I'm the kind of
person I like to look at the outlier so
not the bulk but you know the special
ones and they just need to be treated in
a different way and there needs to be an
acknowledgment of that different ways
for different things so uh big data can
look at uh divorce rates
and uh perhaps you and I are more
interested in the individual love
stories yes
um so
I don't know if it's possible to say but
what do you think is the big discoveries
that are waiting
uh is it on the different dynamics of
the yield
the common narrative the common story of
how some of these metal poor stars are
formed
is it where are the discoveries in this
field that you think will come
I think the individual discoveries are
actually
we've made most of those certainly
through individual Stars
um finding yet another second generation
size incredibly important for me but
isn't isn't really going to move the
needle
finding 50 of them or 100 of them that
would move the needle but that's in
order or two magnitudes up
and new search techniques and new uh
surveys may enable that but would you
still call that a discovery
right so that's just a scale that's a
scale yes so I think about it more like
literally of the puzzle let's say you
have a thousand piece puzzle and you
know you have 900 pieces in there
if you're a person like me I want to get
to the last ones I'm not gonna leave it
it's like okay I see broadly what this
is going to look like right I'm done now
no I want to get to the last one
so is the picture globally going to
change no
are we going to figure out all the
details and how it really works yes
right so really careful getting detail
into it the the ancient uh the ancient
stars of our universe yeah because I
think that's what many of us scientists
are a real little bit detailed obsessed
but I think that's that's our job too
right to really kind of make it airtight
to really walk away saying I fully
understand this not just broadly
but you know I really know we really
know now and so more and more of that is
going to happen
um and so I think this is probably true
across astronomy these individual
10 Sigma discoveries become less and
less
if they were easy we would have made
them already right which means we have
made many of them but really filling in
the details is is is is is the next sort
of level of Discovery maybe we need to
find a new word for that
um
the hopes and expectations that go along
with the word Discovery are so enormous
we we may not always be able to live up
to that but it doesn't mean that we're
not finding out new things it's just a
different kind of quality because the
questions have shifted you close one
door suddenly that 10 new open doors
that that we want to explore and March
through and that's the you know finding
these last puzzle pieces here and there
that Miri make it airtight so there's a
lot of value a lot of power and Beauty
to the discovery
in the big picture of our universe and
in the details yeah we need both
absolutely
uh perhaps drifting into the
philosophical uh let me ask about the
Big Bang as we kind of encroach onto it
so your work is kind of taking steps
back through time in a weird way
do you think we'll get to deeper and
deeper understand
the really really early days of the Big
Bang
and um the philosophical question do you
think we'll be able to understand what
was before the Big Bang
or why the Big Bang happened you think
about that stuff
um not with stars For Better or For
Worse because you know Stars only probe
the time when they were formed and the
Big Bang is surely before then I mean I
I often talk to my students about the
difference between math and physics let
me give you an example um we talked
earlier about 80 1523 and you know I I
was happy to to share with you that I
measure thorium and uranium but I
actually didn't quite close that Loop so
we we did this to try to attempt to
calculate an age for these Stars right
um but they rely on us knowing how the r
process works how these elements are
created where it happens and then how
those elements get dispersed into the
gas and end up in the next Generation
store so quite a few question marks so
that's how we got to the age of 13.2
billion years this is probably not
accurate but this is the best
calculation we could do
um and uh the reason why I'm bringing
this up is that that was actually the
average of multiple
um Elemental ratios that each gave a
certain age and then we average that
because For Better or For Worse this is
the best we can do so some of these
numbers said oh this star is 15 billion
years old and then others said oh this
is 10 billion years old and so I often
use that in my class to say like
what's the good news and what's the bad
news here some ratio said 15 something
10 right is 15 correct
and then I asked to ask them and some
people will say something
and so the the thing here is that it's
an absolutely correct calculation given
the mathematical and physical model that
we constructed but does it make sense no
it doesn't if we believe the universe is
13.8 billion years old
15 is is ridiculous yet it is correct
isn't that interesting correct from a
mathematics perspective it is not
incorrect because this is what I
calculated nobody made a mistake now we
can question whether that's a good model
but that's that's a separate issue so
you're saying physicists are much closer
to truth than mathematicians well it
depends yeah sometimes yes and sometimes
no right so yeah what our job as
physicist is is to take the mathematical
model calculate our numbers and then ask
the question does this make sense right
now
in the case of 15 it doesn't but we took
the average anyway because
that was the the best we could do right
so all right let's put that aside let's
apply the same sort of thinking to the
Big Bang right math can tell us things
that we as physicists cannot grasp
because it doesn't make sense to us now
in the case of the big band that's big
bang that's a special case because we
don't actually know what's supposed to
make sense yeah and this is where things
get interesting but this is where math
will ultimately be the winner because we
can no longer say this makes sense or
this doesn't make sense because the
physics is broken down but math breaks
down too in the singularity of things
well or no depending on who you ask okay
sure sure this is this is the current
question right how far how much further
can we push math let's say to the front
of the Big Bang if there is such a thing
um what's the front in the back what's
the front before the Big Bang the front
okay
so how far can we let the math go before
that stops to make sense right and I
don't know what the answer is to that
but it's it's really cool that because
math doesn't have is not limited by of
our physical nature
it can probably go a little bit further
than the physics yeah right and math can
go into uh
more Dimensions than four dimensions
comfortably and it's it's judgment free
because it just calculates things on its
own whereas as physicists we are so
judgmental yeah this makes sense this
doesn't make sense right it doesn't get
any worse it's such a beautiful dance
it's such a uh it's so amazing that
through this dance you can explore the
origins of the universe
like
doesn't the Big Bang just blow your mind
that this thing has just started from a
point
yeah and now we're here yeah yeah yeah
hydrogen and helium and then all the
stuff you're studying
I mean this this this evolution of
chemistry created
humans
and we're here talking
and there's a lot more to the story
it's amazing yeah yeah yeah uh
and this kind of March that you're doing
is observing data
and is there
foreign
you're looking at old light on old data
but only a few thousand years right just
a few thousand that's that's the
difference between me and my jwst
colleagues yes their objects that light
has traveled 13 billion years or
whatever it was to us and they're
observing that now my light has only
traveled a few thousand years it's it's
nothing so whatever You observe now is
likely still going on yes these stars
are alive and kicking and having a blast
Thousand Years
just a few thousand years that all it
takes if we can travel close to the
speed of light
yeah maybe we can reach out there
we wouldn't have any planets around
those tasks though so that's is that a
definitive intuition well what are
planets made of elements right to take
the Earth as all Heavy elements right
the universe needed to reach a certain
stage first to have produced enough of
all these elements to actually make a
planet so on average you've got so okay
right so that took quite a few billion
years so they're not going to have a
mechanism for forming planets you could
have visitors probably but the the the
kinematics of that are weird are
unlikely yeah I would say so
so they're interesting in that they
reveal the early chemical evolution of
the universe yes not that they're uh
they could be good vacation spots but
not well there's nothing like a warm
it's just not no Planet Islands to to go
to to chill
in your book you highlight the major
contributions in the field uh by many
women some of these women were not as
you describe
immediately credited for their
discoveries so for me from from computer
science perspective
uh the story also tells Harvard
computers uh who were these women and
what can you just say about the nature
of science and Humanity discovering
things is is in is part of the human
nature right and so it has happened for
the longest time
um not just by men but also by many
women
um the field of Stella astronomy which
is is my field has particularly
benefited from from many discoveries
made by women you mentioned the Harvard
computers that's uh a term used for uh
women who worked about a hundred years
ago at the Harvard College Observatory
and they were hired for their low wages
and willingness to do diligent and
patient work to comb through
the Big Data of the day so the
observatory director they were carrying
out large Sky surveys at the time and
they needed uh
that that data needed to be processed
and looked at and analyzed and so many
women or several dozens or one or two
dozen women over over the years where
um were hired to to do this work and in
the process
because they were looking at the actual
data and they were smart even though
they had often no formal education
they made a lot of discoveries simply by
by being in tune with what they were
doing so they weren't robots as you know
the term computer would perhaps let on
uh lead on um so any Jump Cannon
classified
thousands and thousands of Spectra and
found out that uh you can you know
stores have different temperatures and
their Spectra look according we still
use the classification sequence today
um Cecilia Payne gaposhkin later on in I
think 1925 was one of the first women to
obtain a PhD
uh in in Stella astronomy and she
figured out she calculated that the sun
is mostly made of hydrogen and helium
that seems normal to many of us these
days but at the time it was thought that
celestial objects are made of the same
thing as the Earth
it's a gutsy amazing Discovery yes it
was later termed the most important
thesis of humankind or something like
that
what a revelation to realize that stars
are made of hydrogen and helium right
and this was exactly the time when
people figured out why stars are shining
namely because of nuclear fusion and
that its protons and you know the
tunneling effect that leads to to the
actual Fusion otherwise you know you the
the protons repulse each other they
don't come together
and so what an incredible time it was
back then and so stars and nuclear
physics were very closely related and
and it remains that now it's called
nuclear astrophysics
and so many women had many uh
contributions to that of course prior to
that Marie Curie uh discovered two new
elements
ah so awesome
um uh radium and polonium
discovered nuclear fission that is the
basis for understanding the our process
this is exactly what happens
uh in in the our process you know the
heavy nuclei let's say uranium if you
bombard it with a neutron
we talked at length about it it will
Decay it will well not Decay actually it
will fission it will split into barium
and Krypton let's say so two lighter
elements that's exactly what we observe
I have always a higher abundance of
barium than the heavier elements because
of this fission cycling that she
calculated
uh in 1938
um so many many contributions and it's
it's just so remarkable if you just take
that body of work
that that changed how we
how we do things how how we see the
Universe
um how we understand things
has led to so many subsequent
discoveries good ones and bad
um well we did all of it is taken
together that's progress right it's it's
ultimate science is what it is we have
to decide what we do with that knowledge
right we can always use things for good
or for bad
um that's that's part of the human uh
Endeavor as well and also part of the
human endeavor and the human nature is
the issues with corruption and credit
assignment and all these kinds of things
that make this whole ride so damn
interesting about what's right and wrong
and about the nature of Good and Evil
yeah and that seems to surface itself in
all kinds of places all the time yes yes
Lisa Maynard was nominated for the Nobel
Prize 40 times more than that even it's
amazingly she holds the record for that
she never received it uh so I guess in
point
um yeah and of course the Nobel Prize is
its complexities one is the credit
assignment but two even in astronomy
sort of assigning credit to a handful of
folks on so many more contributed as a
complicated story also yeah it's very
complex
okay sorry for the Romantic question but
what to use the most beautiful idea in
astronomy in Stellar astronomy
well
when I was in high school I I was
thinking like okay well what what what
do I want to do when I'm growing when I
grow up right I knew I wanted to do
astronomy but I was a little bit torn
because my interests were definitely
Stars Stella astronomy but also
chemistry I always had a Fascination
about the elements so Marie Curie was
was a a big role model
um my friend actually made a beautiful
produced a beautiful movie about the
discovery of um of of the elements this
is the theater play but digitized
where when I thought I could actually
kind of relive this sort of Discovery
moment that that Marie Curie had it sent
shivers down my spine it was fantastic I
mean this is
this is the kind of thing that that I
wanted to experience
um but yeah so nuclear physics and
element creation information was really
interesting to me chemistry the elements
stars and all of that and I was like
I don't know if I ever find something
that combines all of these things
and then I ended up in Australia and I I
met this this person and he was working
on Old stars and as I was sitting in his
talk hearing about this for the first
time
it kind of it clicked all over my head
and it's like oh my God it it all fell
in place because we can use these old
stars to study the elements to learn how
they're formed we can get these clean
signatures that help us inform the
nuclear synthesis processes you know and
I know of course I need to know a lot
about stars too so it's it's like all
together and that that was sort of a
moment of magic
and then the fact that
I have now done that for 20 years this
is just like I won the lottery it all
clicked into place so in some sense it's
an it's an ongoing love story for me if
I could say it like that where you know
I found my stars my thing and I am
fortunate enough to be able to keep
doing that and I'm happy to
see where where it will take me you know
it's an evolution as with every
relationship you have to if you don't
March forward you move backwards I'm not
interested in moving backwards so I'm
I'm letting the field and the
discoveries and the findings lead me to
you know and I'm often
um
I'm I'm it's it's not hard for me to
follow sort of my hunches and sometimes
even at the telescope it's like
let's take a look at this one I have a
good feeling and then usually something
good or you know not bad
pop pops out at the end and I
um I really like that hey that I have
the freedom to to do that that I'm
allowed to follow my hunches
um too many people I think are sort of
boxed in with their job or their life
that they they don't have that kind of
Freedom that that's really important to
me and I certainly try to make use of
that I also try to teach that to others
to trust them to learn you know you need
to learn your things but then you need
to also trust that knowledge and that
you have a grasp on it right you get out
what you put in
and
um being able to contribute in
meaningful ways to our knowledge about
our Cosmic ancestry our Cosmic history
um
that that's that's a wonderful thing and
and in this way your personal love story
with the Stars evolves
what advice you've already spoken to it
a little bit but what advice would you
give to young people that are trying to
find the same kind of love story in
their career in their life
increasingly hard for folks to to find
that
um sometimes I feel
um that you know young people uh have
all the opportunities these days and
that's that's wonderful but it's almost
like that leads to some
what's the right word they're they're a
little bit of tired of too too tired to
make all the decisions because at some
point you need to put your eggs in a
basket and you need to be okay with that
we can't do all the things even though
we're often told you can be president
too and I think that's really important
to convey but at the end of the day we
can only have sort of one job or one
type of profession I'm not saying you
know you need to be locked in but
um it's hard to change 180 degrees
and and so lots of people I think are
often afraid to
to really dig in at least for some time
and get the hands real dirty
and really learn from the bottom up on
one thing on one thing because they're
afraid they're missing out on on 99
other things
but life is a little bit missing out on
99 other things because we only have 24
hours in a day I
I have that feeling very often there are
so many things I would like to do many
things I would like to try to be good at
sometimes I wish I had a different job
you know because I have other interests
too but I realized okay I can only do
one thing so I have no regrets but this
is this is a general feeling that I
think
I would think most of us have but if it
lets if it stops you from really digging
drilling down on one thing to become an
expert in one thing to become really
good at one thing that you call your own
then that it just makes it difficult
and so a fulfilling life
is in part likely to be discovered in a
singular pursuit of a thing of one thing
well yeah for at least for a time yeah
for some time with your with your heart
and your hands
um because I think most people long to
own something
you know we all
I think want to leave some Legacy of
some sorts you know for our children for
Humanity for this planet
and I think
it's really important for young people
to strive for that and not lose sight or
trade that for all the opportunities
because an opportunity is nothing if you
don't do anything
you need to you need to do something at
the end of the day so I chat with lots
of people about this and I often start
by just saying hey tell me what you
don't like
because it's often much easier to to
narrow down narrow down narrow down let
out what what's not on your plate yeah
and then this way we get a little bit
closer and then it's like well why don't
you take a risk yeah and just sign up
for something for three months but
that's what it feels like that that's
what it feels like and it is that is a
risk commitment is a risk yes because
it's you're basically sacrificing all
the other possible options but then I
guess you have to trust the magic you
you noticed in that thing yes if you
notice one thing just stick with it and
then and then maybe there's something
there right right and and this moment of
kind of feeling it in in your entire
body and mind that this is the right
thing you know getting there is is
probably really hard but if you don't
try you won't find out right the hard
stuff is the fun stuff that's also
another thing you find out and then
there's that yes somehow it doesn't make
sense uh you also mentioned that uh
you've taken a little stroll into the
artistic representation of yourself uh
can you can you speak to that for a
little bit yes
I already just mentioned
I wish I I you know had more time to do
other things
I find little little
um sideways I guess to to pursue things
that that I like besides astronomy or at
least I try to find connections and so
um some years ago I
um again with the help of of my friend
who made this Marie Curie movie uh she
and I wrote a one-woman play where I
actually portray Lisa midna who was an
Austrian German physicist nuclear
physicist I'm from Germany so I have the
right accent for that
uh and we wrote this play about this
moment of discovery of nuclear fission
again this is an absolutely critical
piece that explains my work today
and we all stand on the shoulder of
giants she was one of those Giants and
in some ways it's it's of course a way
for me to acknowledge other people's
work that have come before me it's a
wonderful way to highlight
um the contribution by a prominent woman
and the way I I do it is it's a 25
minute play in costume
where I relive for people the moment of
discovery
then I turn into myself
and then I give a 30 minute presentation
on the r process and the creation of
heavy elements because the audience can
now perfectly understand that the public
audience given the historic backdrop of
this discovery that they just lived
through my presentation
and it's it's a wonderful compliment
that almost spends 100 years from one
woman to the next passing on the torch
and
you know when we write up our results in
let's say you know in magazines like
Nature and Science it's always about the
results on the gold platter perfectly
prepared
it's the discovery is never described
only ever the results
you asked me beforehand right what does
it feel to be at the telescope in this
moment right
I'm happy to talk about this but it's no
way of written ever nobody nobody really
talks about it and so having a form of
uh you know theater of the Arts to bring
this this exciting moment that that is
what we all want to experience as
scientists to a wider audience is so
profound and so rewarding and they all
love it because everyone can understand
a moment of Discovery I was looking for
something and then I found it it's like
you misplaced car keys right
or love it yes yes it everyone can what
the Glorious experiences yes the the
implications and the findings that is
much harder to understand for the for
anyone this is where the scientists work
truly lies this is our job but the
moment of Discovery is easy
and it's beautiful and it needs to be
said and so taking my audience on this
journey what is the perils what are my
worries and then ah here is the moment
of Discovery let me tell you about it it
profoundly transformed me and here
here's how it went right it it it's so
good and art is a way to reveal this
fundamentally Human Side of science yes
it's the problem with science is that's
people doing it
that's also what makes it beautiful
right yeah humans are fascinating and
that we're able to come up with these
ideas through all the struggle through
all the hardship through all the Hope
through all the search
and so the art is a great way to to
portray that and to broadcast that right
I think this is how the audience really
should be interacting with Scientists
much less about the findings but really
more about this Yearning For answers
right I need to find these khakis I need
I need it because I need to go right
it's like now now and then oh God here
it is now I can go my my Merry ways it's
it's so relatable yeah we just need to
find more and better ways to to do that
so I hope to turn this into also a
digitized version at some point to again
make it more accessible
I hope so too so far I'm just doing it
in person
but it's I would love it I think a lot
of people would love to see it so I hope
you do just that let me ask you a big
ridiculous question you look up at the
stars you look up at the early
early Stars
so let me ask the big question that we
humans often ask and struggle to answer
what's the meaning of this whole thing
why why are we here
the biological evolution requires the
chemical Evolution for all of this to
kind of play out
and carbon played this important role
and you know in some sense we're just a
consequence of all of these things being
the way they are right so
maybe this is just where we are supposed
to be because you know the laws of
physics sort of work the way they do and
um we talked much about the variety of
of everything really in certainly you
know from over here to over there and
things in the vicinity of where the sun
and the solar system formed they were
the way they were and life maybe wasn't
necessary consequence of that
I in some sense I like to believe that
because then it becomes reproducible and
we can apply that same argument
elsewhere if it's total chance right
that makes it harder and that's not not
truly satisfying to to a scientist
so it's uh as a consequence
of psychological Evolution which is the
consequence of biological evolution
which is consequence of chemical
Evolution consequence of physical
Evolution whatever whatever disciplines
it's uh turtles on top of turtles
turtles all the way down yes
yeah
I studied some of the most ancient
turtles yes at the very bottom of the
thing
that's right they live for quite a while
yeah they do
well uh thank you for your incredible
work thank you for uh highlighting both
The Human Side and and the Deep
scientific side it's just I'm a huge fan
of you working thank you for everything
you do and thank you for talking today
this is awesome of course it was
wonderful thank you
thanks for listening to this
conversation with Anna for Bell to
support this podcast please check out
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let me leave you with some words from
Douglas Adams in Hitchhiker's Guide to
the Galaxy
far out any Uncharted backwaters of the
unfashionable end of the western spiral
arm of the Galaxy lies a small
unregarded yellow sun orbiting this at a
distance of roughly 92 million miles is
an utterly insignificant little
blue-green Planet whose Aid descendant
life forms has so amazingly primitive
that they still think digital watches
are a pretty neat idea
thank you for listening I hope to see
you next time