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

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

00:06 We're made of star stuff

00:08 This term was coined by the astronomer Carl Sagan 50 years ago, and it since made it into pop culture

00:16 But what does that even mean and is it true?

00:19 Let's see what the universe has to say about this

00:23 Welcome to chasing starlights. I am Susanna Randall an astronomer at the European Southern Observatory ESO and

00:29 Apparently I am made of star stuff

00:33 And so are you

00:37 Take a look at your body. You can see that you're made up of skin bones muscles and bones

00:43 And you're made of stars

00:47 Take a look at your body. You can see that you're made up of skin bones muscle if you zoom in with a microscope

00:54 You'll find that we're made up of cells and if you go even deeper zoom in even further

00:59 You'll see that at the atomic level. We're made up mostly of six elements

01:04 hydrogen oxygen carbon nitrogen calcium and phosphorus

01:09 And to tell you where these elements come from I have to start at the very beginning at the big bang

01:15 Big Bang

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

01:28 And what happened after that is basically it expanded and cooled down

01:32 after about 400,000 years the universe had cooled enough for the first stable atoms to form and

01:40 Unsurprisingly, these were the simplest atoms. So we had some helium as well as traces of other elements

01:46 But mostly the universe was made up of hydrogen the simplest of all elements consisting of just one proton and one electron

01:53 So that means my body is made up to 10% of

02:01 Something that comes from the Big Bang and that makes me a lot older than I care to think about

02:07 But you can't make up something as complex as the human body of just helium and hydrogen

02:14 So where do the other more complex elements that make up our body and the rest of the universe come from?

02:21 The first elements in the universe formed diffuse gas clouds called nebulae where stars form

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

02:41 So what happened in the nebula is that there were regions that were a little bit denser than others and these regions started accreting

02:49 more and more mass until they started to collapse in on themselves

02:53 And in the inside of this core the temperature pressure and density increased more and more and more until

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

03:06 Our own star, the Sun, was created exactly this way 4.5 billion years ago

03:14 And since then it's been happily fusing away hydrogen to create helium in its core

03:20 But it's not really making any of the other more complex atoms that our body is made of

03:27 For that to happen we need to wait just a little longer

03:31 When the hydrogen in the core of the star has been used up, things start happening very quickly

03:45 The star enters a new phase of its life called the red giant phase

03:51 The outer envelope of the star expands and cools, hence it becomes a giant

03:56 And the inner part, the core, keeps on contracting until the temperature is high enough for helium to start fusing

04:03 And the helium then creates carbon and oxygen

04:07 So carbon and oxygen were two of the other elements that our body is made up of

04:14 And they make up about 84% in mass of our body

04:19 So the majority of the atoms in my body are actually created deep inside stars in these incredibly hot stellar furnaces

04:28 But wait, that means that the carbon and the oxygen are locked inside the core of the star

04:37 How do they get out?

04:39 Well, as it turns out, even stars don't live forever

04:43 When the helium runs out in the core of the star, if the star is not massive enough to fuse heavier elements, then it stops there

04:51 And stars with a similar mass to our Sun, so low-mass stars, can't make elements that are heavier than carbon and oxygen

04:58 Instead, the carbon-oxygen core slowly cools down

05:02 It's this very dense end product of a star called a white dwarf

05:06 And the outer layers are ejected into space

05:09 They form these beautiful arcs, rings, spirals, shells

05:14 In other words, star stuff

05:17 On the other hand, stars with more than about eight solar masses continue to fuse elements in their core

05:34 And they create heavier and heavier elements, as heavy as iron

05:39 But at some point, even they have to die, and they go out with a bang

05:43 They explode as supernovae

05:46 Fun fact, a supernova occurs roughly every 10 seconds

05:50 So that means that by the time I finish this sentence, a supernova will have gone off somewhere in our universe

05:56 During the supernova explosion, even heavier elements are created

06:02 And these are the really glamorous ones, like gold or platinum

06:07 These are hurled out into space by the explosion, giving us sparkly star stuff

06:14 Ironically, stars need to age and die to form the remaining building blocks of life

06:26 So we have nitrogen, which is important for the synthesis of our DNA

06:32 And we have also calcium and phosphorus, which are important for our bones and teeth

06:38 As it turns out, Carl Sagan was right

06:41 We are literally made up of star stuff

06:44 And the story of stars and their lives is also the story of the elements that make up our body

06:50 We're all part of this grand cosmic cycle

06:56 But before you get too excited, cockroaches are also made up of star stuff

07:02 I don't know about you, but I suddenly feel entirely at one with the universe

07:08 [Music]

07:16 I really hope that you enjoyed this episode of Chasing Starlight

07:20 If you did, please press the subscribe button and also activate the notification bell

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07:29 If you have any comments, please leave them below

07:32 For every episode, we will answer some questions

07:35 [Music]

07:37 [Silence]

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