Are We Really Made Of 'Star Stuff?' Learn About Your Body's Elements

Space.com

Astrophysicist Suzanna Randall explains where the elements in our body come from in this episode of "Starlight" from the European Southern Observatory.   Credit: ESO  Directed by: Martin Wallner, Luis Calçada, Martin Kornmesser Hosted by: Suzanna Randall  Written by: Claudia Sciarma, Jonas Enander, Bárbara Ferreira Editing: Martin Kornmesser Videography: Angelos Tsaousis Footage and photos: ESO/M. Kornmesser, ESO/L. Calçada, Natural History Museum, fermilab, Ted Johansson (Fellingsbro folkhögskola, Sweden), Cosmos: Ann Druyan, Carl Sagan, Steven Soter, ESO/Meingast et al. Music: Johan B. Monell, movetwo, Luis Calçada, videvo Animations & Infographics:  Luis Calçada, Martin Kornmesser, Martin Wallner Web and technical support: Gurvan Bazin and Raquel Yumi Shida Scientific consultant: Juan Carlos Muñoz Mateos, Paola Amico Filming Locations: ESO Supernova  Produced by ESO, the European Southern Observatory

Transcript

00:00We're made of star stuff. We are a way of a cosmos to know itself.

00:07We're made of star stuff.

00:10This term was coined by the astronomer Carl Sagan 50 years ago, and it's since made it into pop culture.

00:17But what does that even mean? And is it true?

00:21Let's see what the universe has to say about this.

00:30Welcome to Chasing Starlights.

00:36I am Susanna Randall, an astronomer at the European Southern Observatory ESO.

00:41And apparently I am made of star stuff.

00:47And so are you. Take a look at your body.

00:50You can see that you're made up of skin, bones, muscle.

00:54If you zoom in with a microscope, you'll find that we're made up of cells.

00:58And if you go even deeper, zoom in even further, you'll see that at the atomic level, we're made up mostly of six elements.

01:05Hydrogen, oxygen, carbon, nitrogen, calcium and phosphorus.

01:11And to tell you where these elements come from, I have to start at the very beginning, at the Big Bang.

01:17In the first few hundred thousand years after the Big Bang, the universe was a dense, hot, gooey plasma.

01:30And what happened after that is basically it expanded and cooled down.

01:35After about 400,000 years, the universe had cooled enough for the first stable atoms to form.

01:41And unsurprisingly, these were the simplest atoms.

01:44So we had some helium as well as traces of other elements.

01:47But mostly the universe was made up of hydrogen, the simplest of all elements, consisting of just one proton and one electron.

01:56So that means my body is made up to 10 percent of something that comes from the Big Bang.

02:05And that makes me a lot older than I care to think about.

02:09But you can't make up something as complex as the human body of just helium and hydrogen.

02:16So where do the other more complex elements that make up our body and the rest of the universe come from?

02:26The first elements in the universe formed diffuse gas clouds called nebulae, where stars form.

02:34In fact, we can still see stars forming in these nebulae today, like in the spectacular image taken by ESO's Vista telescope.

02:42So what happened in the nebula is that there were regions that were a little bit denser than others.

02:48And these regions started accreting more and more mass until they started to collapse in on themselves.

02:55And in the inside of this core, the temperature, pressure and density increased more and more and more

03:01until the temperature was high enough for hydrogen fusion to start and a star was born.

03:09Our own star, the Sun, was created exactly this way 4.5 billion years ago.

03:15And since then, it's been happily fusing away hydrogen to create helium in its core.

03:22But it's not really making any of the other more complex atoms that our body is made of.

03:28For that to happen, we need to wait just a little longer.

03:40When the hydrogen in the core of the star has been used up, things start happening very quickly.

03:46The star enters a new phase of its life called the red giant phase.

03:52The outer envelope of the star expands and cools, hence it becomes a giant,

03:57and the inner part, the core, keeps on contracting until the temperature is high enough for helium to start fusing.

04:04And the helium then creates carbon and oxygen.

04:10So carbon and oxygen were two of the other elements that our body is made up of

04:15and they make up about 84% in mass of our body.

04:20So the majority of the atoms in my body are actually created deep inside stars in these incredibly hot stellar furnaces.

04:33But wait, that means that the carbon and the oxygen are locked inside the core of the star.

04:38How do they get out?

04:40Well, as it turns out, even stars don't live forever.

04:44When the helium runs out in the core of the star,

04:47if the star is not massive enough to fuse heavier elements, then it stops there.

04:52And stars with a similar mass to our Sun, so low-mass stars, can't make elements that are heavier than carbon and oxygen.

04:59Instead, the carbon-oxygen core slowly cools down.

05:03It's this very dense end product of a star called a white dwarf.

05:07And the outer layers are ejected into space.

05:11They form these beautiful arcs, rings, spirals, shells, in other words, star stuff.

05:28On the other hand, stars with more than about eight solar masses continue to fuse elements in their core

05:35and they create heavier and heavier elements, as heavy as iron.

05:41But at some point, even they have to die, and they go out with a bang.

05:45They explode as supernovae.

05:48Fun fact, a supernova occurs roughly every 10 seconds.

05:52So that means that by the time I finish this sentence, a supernova will have gone off somewhere in our universe.

06:00During the supernova explosion, even heavier elements are created.

06:03And these are the really glamorous ones, like gold or platinum.

06:10These are hurled out into space by the explosion, giving us sparkly star stuff.

06:21Ironically, stars need to age and die to form the remaining building blocks of life.

06:28So we have nitrogen, which is important for the synthesis of our DNA.

06:33And we have also calcium and phosphorus, which are important for our bones and teeth.

06:40As it turns out, Carl Sagan was right.

06:43We are literally made up of star stuff.

06:46And the story of stars and their lives is also the story of the elements that make up our body.

06:52We're all part of this grand cosmic cycle.

06:58But before you get too excited, cockroaches are also made up of star stuff.

07:03I don't know about you, but I suddenly feel entirely at one with the universe.

07:11I really hope that you enjoyed this episode of Chasing Starlight.

07:16If you did, please press the subscribe button and also activate the notification bell.

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07:24If you have any comments, please leave them below.

07:27For every episode, we will answer some questions.

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