WEBVTT

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ANNA FREBEL: Have
you ever wondered

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how all the chemical
elements are made?

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Then join me as we are lifting
all the stardust secrets

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to understand the cosmic origin
of the chemical elements.

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We want to talk about the cosmic
origin of the chemical elements

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today.

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In order to understand where
the elements come from,

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we need to consider two
different components--

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one is nuclear physics
and one is astrophysics.

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When the nicely
combine, when we want

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to understand where the
chemical elements come from,

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and so let's look at
that in more detail.

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We have the nuclear
physics part.

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And we have astrophysics.

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And on the nuclear
physics side, we

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have two things that we want
to consider or learn about,

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namely how the light
elements are formed,

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light elements up to iron.

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And they are formed in
fusion processes in stars.

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Fusion processes.

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And so this is one.

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And then we have
also lots and lots

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of elements on the
periodic table that

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are heavier than iron.

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So how are the heavy
elements formed?

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That would be heavier than iron.

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And so they are made
in what's called

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a neutron-capture processes.

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And that's a really neat way
of making big heavy nuclei.

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And so these two
parts here together

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really explain how most of the
elements in the periodic table

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are made.

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And there are a
few extra processes

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that we will not consider.

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But this gets us almost there.

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Then we have the astrophysics,
because this is basically

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a lot of theory.

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And we need to put
this to the test.

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And one test that
the universe offers

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us is investigating
chemical evolution.

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Chemical evolution is that
the successive build up

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of heavy elements in
the universe with time,

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with cosmic time, over the
last 13.8 billion years.

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And we can observe
stars at different times

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and thus trace the signatures of
these nuclear sort of processes

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here and reconstruct how the
nuclear physics operated.

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That works particularly
well at early times

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when the universe was
a much less messy place

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than it is now.

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And so the second
portion here is

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going to be the oldest
stars because they

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are the tool for us
to really figure out

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how the elements were made
first in the universe.

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That allows us to again
obtain clean signatures

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of these processes there.

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And that's a very exciting and
timely avenue for us to study.

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And together with
the older stars,

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comes the concept of
stellar archeology.

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And that sort of
encompasses how we

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use stars that are still
available and shining today

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to study the early universe
when everything got started.

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And in order to study chemical
evolution with old stars,

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we actually need to use a
scientific method called

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spectroscopy.

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So we're also going to look
at spectroscopy and how

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that works, observing all the
little stellar little rainbows.

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And because we do that
with big telescopes,

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we're also going to look at what
it's like to use big telescopes

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and observing.

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Because all of
this work is based

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on astronomical observations
with the largest

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telescopes, mostly in Chile.

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And I will explain all these
different parts one by one.

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And then in the end,
we're going to put it

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all together to understand
the origin of the elements.

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