Uploaded August 2021 | Updated September 2026, 2 hours ago
If you'd like to support me in this adventure of creating a home-made Masters level course for everyone, please consider donating $1/month at patreon.com/spacebutmessier
The famous Science Communicator Carl Sagan once said,
“The cosmos is within us. We are made of star-stuff. We are a way for the universe to know itself.”
Now, He’s not talking about our chakras or releasing positivity into the universe- No, he is literally talking about our physical beings. We are made of star stuff.
In this video of our Astronomy Masters Program, we’ll learn how we, humans, we literally created by far away stars in the universe.
If you haven’t watched my last video on how the universe began, check it out here for a little background on this section.
You see, what Carl Sagan really meant, is that the atoms and molecules that make up your blood and bones, we once at the center of an explosive death of a star across the vast reached of space.
Now, this next part is complicated but we are taking a deeper dive in a later chapter so hold tight. You see, as galaxies formed and matter within galaxies clumped together, their gravity rose, they pulled in more matter and eventually the the pressure was so intense in the center of these clumps that hydrogen, which is what made up almost all of the universe, hydrogen atoms fuses together to form helium. This process is known as nuclear fusion and it produced a lot of energy. Now the balance of the nuclear fusions energy outward and the gravity’s forces pulling inward creates what we know as a star. A huge ball of gas and dust constantly giving off energy (or light and heat) by converting hydrogen to helium.
Okay great, we’ve got hydrogen and helium covered, but are we made of that? Haven’t I heard something about carbon or skin? Like what is my skin made out of?
Hold tight. We are getting there.
You see with stars, we have observed them to have a life cycle. They are born, they live in a balanced state called hydrostatic equilibrium. Basically when the outward nuclear pressure equals the inward force of gravity. Then after millions and billions of years of this balance or equilibrium, they run out of hydrogen to burn. They run out of fuel. They don’t produce any more outward pressure and gravity wins, pulling all of that material to its center and exploding it across space. In fact, The most massive stars die in insanely massive explosions called supernovae. The released matter mixes with other matter floating between the stars in the galaxy, eventually becoming part of new clouds of gas and dust from which new generations of stars can be born. So galaxies are basically cosmic recycling plants, recycling material expelled from dying stars into new generations of stars and planets.
So let’s get back to the question. I’ll give you this freebie. If the early universe only contained hydrogen and helium, how were we, humans, who are made of carbon, nitrogen, oxygen, and iron created? . Where did these other elements come from?
Evidence shows that these massive explosions that occur when a star dies can convert hydrogen and helium to these heavier elements over time. In fact, by the time our solar system formed, about 412 billion years ago, earlier stars had already converted up to 2% of our galaxy’s original hydrogen and helium into heavier elements like carbon and nitrogen. Therefore, the cloud that gave birth to our solar system was made of roughly 98% hydrogen and helium and 2% other elements. This 2% may sound small, but it was more than enough to make the small rocky planets of our solar system, including Earth. On Earth, some of these elements became the raw ingredients of life, elements that when nurtured by our sun and Earth’s growing natural environment, began the series of evolution that ultimately produced human beings.
In short, the metal in the device you are watching this video from was created inside stars that lived and died before the birth of our Sun, and so were you.
Thanks for watching, please subscribe if you haven’t so you don’t miss next week’s lesson and if you are new to the Astronomy Masters Program, stick around and you’ll see a link to the playlist. See ya!
Animations from ESA/Hubble
Here is the throwback to an old haircut about hydrostatic equilibrium: youtube.com/watch?v=pg4PbqKbwiw
If you'd like to support me in this adventure of creating a home-made Masters level course for everyone, please consider donating $1/month at patreon.com/spacebutmessier
The famous Science Communicator Carl Sagan once said,
“The cosmos is within us. We are made of star-stuff. We are a way for the universe to know itself.”
Now, He’s not talking about our chakras or releasing positivity into the universe- No, he is literally talking about our physical beings. We are made of star stuff.
In this video of our Astronomy Masters Program, we’ll learn how we, humans, we literally created by far away stars in the universe.
If you haven’t watched my last video on how the universe began, check it out here for a little background on this section.
You see, what Carl Sagan really meant, is that the atoms and molecules that make up your blood and bones, we once at the center of an explosive death of a star across the vast reached of space.
Now, this next part is complicated but we are taking a deeper dive in a later chapter so hold tight. You see, as galaxies formed and matter within galaxies clumped together, their gravity rose, they pulled in more matter and eventually the the pressure was so intense in the center of these clumps that hydrogen, which is what made up almost all of the universe, hydrogen atoms fuses together to form helium. This process is known as nuclear fusion and it produced a lot of energy. Now the balance of the nuclear fusions energy outward and the gravity’s forces pulling inward creates what we know as a star. A huge ball of gas and dust constantly giving off energy (or light and heat) by converting hydrogen to helium.
Okay great, we’ve got hydrogen and helium covered, but are we made of that? Haven’t I heard something about carbon or skin? Like what is my skin made out of?
Hold tight. We are getting there.
You see with stars, we have observed them to have a life cycle. They are born, they live in a balanced state called hydrostatic equilibrium. Basically when the outward nuclear pressure equals the inward force of gravity. Then after millions and billions of years of this balance or equilibrium, they run out of hydrogen to burn. They run out of fuel. They don’t produce any more outward pressure and gravity wins, pulling all of that material to its center and exploding it across space. In fact, The most massive stars die in insanely massive explosions called supernovae. The released matter mixes with other matter floating between the stars in the galaxy, eventually becoming part of new clouds of gas and dust from which new generations of stars can be born. So galaxies are basically cosmic recycling plants, recycling material expelled from dying stars into new generations of stars and planets.
So let’s get back to the question. I’ll give you this freebie. If the early universe only contained hydrogen and helium, how were we, humans, who are made of carbon, nitrogen, oxygen, and iron created? . Where did these other elements come from?
Evidence shows that these massive explosions that occur when a star dies can convert hydrogen and helium to these heavier elements over time. In fact, by the time our solar system formed, about 412 billion years ago, earlier stars had already converted up to 2% of our galaxy’s original hydrogen and helium into heavier elements like carbon and nitrogen. Therefore, the cloud that gave birth to our solar system was made of roughly 98% hydrogen and helium and 2% other elements. This 2% may sound small, but it was more than enough to make the small rocky planets of our solar system, including Earth. On Earth, some of these elements became the raw ingredients of life, elements that when nurtured by our sun and Earth’s growing natural environment, began the series of evolution that ultimately produced human beings.
In short, the metal in the device you are watching this video from was created inside stars that lived and died before the birth of our Sun, and so were you.
Thanks for watching, please subscribe if you haven’t so you don’t miss next week’s lesson and if you are new to the Astronomy Masters Program, stick around and you’ll see a link to the playlist. See ya!
Animations from ESA/Hubble
Here is the throwback to an old haircut about hydrostatic equilibrium: youtube.com/watch?v=pg4PbqKbwiw
