ANNA FREBEL: Have you ever wondered
how all the chemical elements are made?
Then join me as we are lifting all the stardust secrets
to understand the cosmic origin of the chemical elements.
We have come to the end of our little journey
where we wanted to explore the origin of the chemical
elements.
[MUSIC PLAYING]
I hope you enjoyed it, and I hope
I could help you to understand that this is actually
not just one origin.
It's a whole process.
And it's a process that's still going on.
So let's summarize what we covered.
Well, we talked a lot about fusion and neutron capture
processes that create all the elements in the first place.
We talked a little bit about where that happens,
I mean the cores of stars, as well as
in supernova and neutron star mergers.
And once these elements are created,
they can then be observed, and they
contribute to the chemical evolution of the universe.
If they are produced in the early universe,
then we can see them in the older stars.
So if produced in the early universe, then
we have this chance of observing clean signatures.
Today, that is not possible anymore,
because chemical evolution has moved on too far.
It's too messy today.
And so, we use the most metal poor stars in order
to detect these clean signatures,
and to work with nuclear physicists
to understand how these processes exactly work,
and in what astrophysical sites that might occur.
So here we have the oldest stars.
And one reason why we can infer that these stars must
be very old, because if there weren't we
wouldn't get these very clean signatures
that were only present at the earliest times.
Now the very fortunate coincidence for us,
is that these older stars actually found in the Milky Way
today, so they are fairly local objects.
And that is a great advantage over very distant galaxies
that are also often used to study the early universe.
We find them in the Milky Way, but we
need the kind of data, of course,
to do a chemical analysis.
And we do that with spectroscopic observations.
And we use the world's largest telescopes for that,
because only they can give us the kind of data quality
that we need in order to measure these tiny little absorption
lines that tell us about the composition of all
the different elements across the periodic table.
And then finally, if we put this all together,
we can determine the chemical composition of our old stars,
and actually we can do so not just of old stars,
but of stars at a variety of ages,
a variety of metal contents.
And that helps us to piece together
how the amount of each metal actually changed with time.
And that's a very exciting prospect.
So that's chemical evolution.
And as I mentioned before, this is an ongoing process.
Much of all the elements are still being produced.
right now.
There's probably a supernova going off right now
as we speak somewhere in the universe
where more elements have been created.
And so, the chemical makeup of the universe is changed again.
So it's continuously changing process.
And that brings us to the end.
So this is really all the star stuff that we are made of.
And while the origin is not entirely
stars, but also stellar remnants, as I mentioned,
supernova and neutron star mergers
should be included in that.
But, yeah, that is really our cosmic origin.
And as humans, it lays in the cosmos, in the cosmic objects,
in a variety of them.
And it takes a whole bunch of processes
in order to unravel that all those stardust secrets.
And one last thing I wanted to mention,
doing this kind of work with all the different elements
has shown pretty clearly that carbon is not only
the most important elements for us humans,
because all lifeforms are carbon based.
It actually turns out, it's also the most important element
in the universe, because at that early time
it needed the carbon to help for the gas
to come together to form small stars in small structures.
And so, I think carbon really plays the most fundamental role
in the universe that we can think of,
because it helps star formation and galaxy
formation, and ultimately planet formation,
and formation of life.
[MUSIC PLAYING]