B1 Intermediate 1 Folder Collection
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Have you ever wondered how all the chemical elements are made?
Then join me as we are lifting all the star dust 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.
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. Wel,l 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, namely in the cores of stars as well as in
supernovae and in 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 oldest stars, so if produced in the early universe, then we have a chance of
observing clean signatures. Today that is not possible anymore because chemical
evolution has moved on to far. It's too messy today. So we use the most metal
stars in order to detect these clean signatures and work with nuclear
physicists to understand how these processes exactly work and in what
astrophysical sites they 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 they 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 oldest
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 a Milky Way but we
need special 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 with 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.
That's a very exciting prospect, well, that's chemical evolution! 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 a continuously changing process and that brings us to
the end. This is really all the star stuff that we are made of and, well, the
origin is not entirely from stars but also a stellar remnants, and as I mentioned
supernovae and neutron star managers should be included in that but, yeah,
that is really our cosmic origin for us humans -- it lays in the cosmos, in the
cosmic object, in a variety of them and it takes a whole bunch of processes in
order to unravel all those star dus 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 life forms 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 and small structures and so I think carbon really
plays the most fundamental role in the universe that we can think of because it
helped star formation and galaxy formation, and ultimately planet
formation, and formation of life.
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Ep. 11: Summary

1 Folder Collection
林宜悉 published on March 30, 2020
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