How Stars Are Formed and Create Galaxies | Big History Project

Summary

This script delves into the cosmic 'Dark Ages' post-Big Bang, a period of uniformity and darkness. It highlights the pivotal role of gravity and matter distribution in the formation of the first stars, which marked a significant leap in cosmic complexity. The emergence of stars introduced light and heat, creating structures from galaxies to superclusters, setting the stage for further complexity and life itself.

Takeaways

• 🌌 The universe was dark and devoid of stars for about 200 million years after the Big Bang, a period known as the Dark Ages.
• 🌑 The early universe was composed mainly of hydrogen and helium atoms, with trace amounts of other elements like lithium and beryllium, and an unknown form of dark matter.
• 🔍 The cosmic background radiation studies revealed an extremely even distribution of matter across the universe, posing a challenge for the emergence of complexity.
• 🌐 The universe's uniformity was disrupted by tiny temperature differences, providing the conditions necessary for gravity to act and create stars.
• 🌟 The first stars formed when gravity clumped together slightly denser regions of the universe, leading to the creation of stars through nuclear fusion.
• 🔥 The process of star formation involved atoms colliding and heating up to extreme temperatures, eventually leading to nuclear fusion and the release of energy.
• ✨ The appearance of stars marked a significant increase in the universe's complexity, introducing light and heat into the previously cold and dark cosmos.
• 🌍 Stars are structured with a core where nuclear fusion occurs, surrounded by layers of plasma through which energy photons slowly make their way to the surface.
• 🌌 Stars are organized into galaxies, with our Milky Way being just one of potentially billions of galaxies in the universe.
• 💫 Galaxies are further grouped into clusters and superclusters, forming large-scale structures held together by gravity, yet still expanding due to the universe's overall expansion.
• 🔑 The Goldilocks conditions for further complexity in the universe are now found primarily in galaxies and around stars, setting the stage for the evolution of more complex entities.

Q & A

What was the Universe like during the Dark Ages after the Big Bang?

During the Dark Ages, the Universe was very simple, cold, and dark, with no stars visible. It was filled with atoms, primarily hydrogen and helium, and a small amount of other elements like beryllium and lithium, as well as dark matter.

Why was the uniformity of the Universe a problem for the formation of complex structures?

The uniformity of the Universe was a problem because it seemed too simple and evenly distributed to allow for the development of complex structures like stars, which are essential for the creation of more complex entities like galaxies and life.

What role did gravity play in the formation of the first stars?

Gravity played a crucial role by magnifying tiny differences in the distribution of matter, causing these areas to clump together and become denser. This process eventually led to the formation of stars as gravity pulled atoms together, increasing their density and temperature until nuclear fusion could occur.

What conditions were necessary for the first stars to form?

The Goldilocks conditions necessary for star formation included a large amount of matter, the presence of gravity, and tiny differences in the distribution of matter throughout the Universe.

How did the cosmic background radiation provide evidence for the uniformity of the early Universe?

The cosmic background radiation showed that matter was extremely evenly distributed across the Universe, with the same temperature, density, and types of atoms everywhere, indicating a high degree of uniformity.

What is the significance of the temperature reaching 10 million degrees in the formation of stars?

At 10 million degrees, protons within the dense cloud of atoms began to collide so violently that they overcame their electrostatic repulsion and fused together, forming helium and releasing a tremendous amount of energy in the process.

What is the 'strong nuclear force' mentioned in the script, and how is it related to star formation?

The 'strong nuclear force' is the force that holds protons and neutrons together in the nucleus of an atom. In the context of star formation, it is the force that holds together the protons after they have fused during the process of nuclear fusion, releasing energy.

How do stars contribute to the increased complexity of the Universe?

Stars contribute to the complexity of the Universe by providing energy in the form of light and heat, creating new structures at various scales, such as galaxies and superclusters, and serving as the birthplaces for heavier elements through processes like nucleosynthesis.

What are star nurseries, and why are they important?

Star nurseries are regions in the Universe where new stars are forming. They are important because they are the sites of ongoing star formation, and they represent some of the most beautiful and active areas in the cosmos.

What is the structure of a star, and how does it relate to the energy production within it?

The structure of a star includes a core where nuclear fusion occurs, producing helium from protons and releasing energy. Surrounding the core is a region where protons are stored and eventually fused. Photons of energy from the core slowly make their way to the surface, taking thousands of years, before being emitted into space.

How do galaxies and superclusters form, and what role does gravity play in this process?

Galaxies and superclusters form as a result of gravity pulling together stars and galaxies, respectively. Galaxies are large structures containing billions of stars, while superclusters are even larger groupings of galaxy clusters, forming vast cosmic webs throughout the Universe.

Outlines

00:00

🌌 The Dark Ages of the Universe

This paragraph delves into the early history of the Universe, following the Big Bang, a period known as the Dark Ages. It lasted for approximately 200 million years and was characterized by an absence of stars, making the Universe cold, dark, and seemingly inhospitable for life. The content describes the composition of the Universe at that time, dominated by hydrogen and helium atoms, with traces of other elements like lithium and beryllium. It also mentions dark matter, although its role was minimal. The uniformity of the cosmic background radiation is highlighted, indicating an even distribution of matter. The paragraph sets the stage for the emergence of stars, which are crucial for the Universe's evolution towards complexity.

05:01

✨ The Birth of Stars and Cosmic Complexity

The second paragraph focuses on the formation of the first stars and their significance in increasing the complexity of the Universe. It explains how slight variations in the cosmic background radiation's temperature allowed gravity to act on these differences, leading to the clumping of matter and the eventual creation of stars. The process involved atoms colliding and heating up to the point where they could no longer hold onto electrons, forming a plasma state similar to the pre-cosmic background radiation era. As the temperature in these dense regions rose to 10 million degrees, protons fused, releasing vast amounts of energy in a process akin to an H-bomb. This energy output created a counterbalance to gravity, stabilizing the structure and leading to the birth of a star. The paragraph also discusses the hierarchical structure of the Universe, from stars to galaxies and superclusters, emphasizing the role of stars as catalysts for further complexity and the ongoing process of star formation observable in star nurseries.

Keywords

💡Dark Ages

The 'Dark Ages' in the context of the video refers to the period approximately 200 million years after the Big Bang when the Universe was devoid of stars and was extremely dark and cold. This term is crucial to the video's theme as it sets the stage for the narrative of the Universe's evolution from a simple, uniform state to one that eventually becomes complex and filled with stars.

💡Cosmic Background Radiation

Cosmic Background Radiation is the remnant thermal radiation from the early Universe, which was released about 380,000 years after the Big Bang. It is a key concept in the video as it provides evidence for the uniform distribution of matter in the early Universe, which is essential to understanding how stars and structures later formed.

💡Hydrogen

Hydrogen is the most abundant element in the Universe, with one proton per atom. In the video, it is mentioned that about 75% of the atoms in the early Universe were hydrogen. Hydrogen plays a central role in the formation of stars, as it is the primary material that undergoes nuclear fusion to produce energy in stars.

💡Helium

Helium is the second most abundant element in the Universe, with two protons per atom. The video mentions that about 25% of the atoms in the early Universe were helium. Helium is also a product of hydrogen fusion in stars, highlighting its importance in the evolution of the Universe.

💡Dark Matter

Dark Matter is a hypothetical form of matter that does not emit or reflect light and is detectable only through its gravitational effects. The video briefly mentions dark matter but notes its limited role in the narrative of star formation. It is a significant concept in cosmology, contributing to the overall mass and gravitational interactions in the Universe.

💡Goldilocks Conditions

The 'Goldilocks Conditions' refer to the just-right conditions necessary for certain phenomena to occur, neither too extreme in any direction. In the video, these conditions are related to the formation of stars and the emergence of complexity in the Universe, such as the right temperature, density, and distribution of matter.

💡Gravity

Gravity is one of the four fundamental forces in the Universe and plays a starring role in the video's narrative. It is the force that causes matter to clump together, leading to the formation of stars and larger structures. The video explains how gravity magnified tiny temperature differences in the early Universe, setting the stage for star formation.

💡Nuclear Fusion

Nuclear Fusion is the process by which atomic nuclei combine to form a heavier nucleus, releasing a significant amount of energy. In the context of the video, nuclear fusion occurs in the cores of stars where hydrogen atoms fuse to form helium, providing the energy that makes stars shine.

💡Stars

Stars are celestial bodies composed of gas that undergo nuclear fusion at their cores, emitting light and heat. The video focuses on the emergence of the first stars as a critical step in increasing the complexity of the Universe, transforming it from a dark and uniform state to one filled with light and structure.

💡Galaxies

Galaxies are vast systems of stars, dust, and dark matter bound together by gravity. The video mentions that stars are gathered into galaxies, such as our Milky Way, which contains billions of stars. Galaxies are a key structure in the Universe, forming larger-scale structures and contributing to the overall complexity.

💡Superclusters

Superclusters are the largest known structures in the Universe, composed of galaxy clusters held together by gravity. The video describes superclusters as part of the large-scale structure of the Universe, highlighting the role of gravity in organizing matter on the grandest scales.

Highlights

The Universe was dark and cold for about 200 million years after the Big Bang, known as the Dark Ages.

Atoms were evenly distributed in the early Universe, with mostly hydrogen and helium, and traces of beryllium, lithium, and boron.

Dark matter was present but played a minor role in the early Universe's story.

Cosmic background radiation studies reveal the uniform distribution of matter in the early Universe.

The uniformity of the early Universe posed a problem for the emergence of complex structures like stars.

The first stars appeared due to the Goldilocks conditions of matter, gravity, and small differences in matter distribution.

Tiny temperature differences in the cosmic background radiation allowed gravity to start forming stars.

Gravity magnified small density differences, leading to the formation of stars through a runaway process.

At the center of dense clouds, atoms began colliding violently, heating up and eventually fusing to form stars.

Stars lit up when the core temperature reached 10 million degrees, initiating nuclear fusion.

Nuclear fusion in stars releases energy, as seen in hydrogen bombs, and counteracts the force of gravity.

The appearance of stars marked the second major threshold of complexity in the Universe.

Stars transformed the Universe from a uniform state to one filled with billions of glowing bodies.

Stars are still forming today in star nurseries, visible through telescopes.

Stars introduced new structures at various scales, from individual stars to galaxies and superclusters.

Galaxies, like our Milky Way, contain billions of stars and are part of even larger structures.

Gravity forms clusters of galaxies and superclusters, creating a cosmic web throughout the Universe.

The expansion of the Universe is observable at the supercluster level, where they move apart from each other.

Stars are key to the emergence of further complexity in the Universe, acting as 'cold campfires'.

The Goldilocks conditions for complexity are found in galaxies and around stars, guiding the next steps of cosmic evolution.

Transcripts

DAVID CHRISTIAN: We've all looked up at the stars at night

and wondered about them.

But, could you imagine what it would feel like

if you looked up at the stars and you saw nothing?

No stars at all?

Well, that's what it was like for about 200 million years

after the Big Bang.

As the Universe expanded,

it got colder and colder

and darker and darker

and, frankly, less and less like a place

that might produce things like you and me.

Astronomers call this part of the Universe's history

the Dark Ages.

During the Dark Ages,

you had a lot of atoms

flowing through space.

You had... about 75 percent of them were hydrogen,

with one proton;

about 25 percent, most of the rest, were helium,

with two protons, and there was a tiny sprinkling

of beryllium, of lithium--

lithium's got three, beryllium's got four protons--

and, finally, boron.

There was also stuff

that astronomers call dark matter,

quite frankly, because they don't understand what it is.

But it doesn't seem to play

much of a role in the story, so we're going to ignore it.

The whole Universe was really very, very simple.

We know this because of studies

of the cosmic background radiation

that was released, you remember, about 380,000 years

after the Big Bang.

What that shows is that matter was distributed extremely evenly

through the Universe.

Everywhere you looked,

you seemed to have the same temperature,

the same density, the same types of atoms.

Really, everything was uniform.

And that's a real problem.

Because it seems as if the Universe

was just too simple, too uniform

for anything interesting to happen.

How could you produce you and me from such a Universe?

Well, we actually know how this happened,

and the key players in all of this are stars.

So what we're going to do in this unit

is we're going to focus on how the first stars appeared.

We'll see throughout this course

that more complex things seem to appear

when you have just the right Goldilocks conditions

for their appearance.

Not too hot. Not too cold.

Not too big. Not too small.

Not too close together. Not too far apart.

You get the idea.

So what were the perfect Goldilocks conditions

for creating just a bit more complexity

in the early Universe?

Well, it turns out that those conditions

were scattered all through the Universe.

The crucial things you needed were:

first, lots of matter;

secondly, gravity;

and third,

tiny differences in the distribution

of that matter.

And they were all there.

Recent studies of the cosmic background radiation,

using special satellites such as the WMAP satellite,

have shown that, in fact, there were tiny differences

in the temperature of the cosmic background radiation.

Some regions, for example, were just a thousandth

of a degree hotter than other regions.

Now, this was just enough for gravity to get to work.

And what gravity could do was to magnify those differences

and turn them into something much more interesting.

And so this is what happened:

gravity began to get to work on those differences,

and eventually it created stars, something entirely new.

So let's see how this works.

Gravity, you'll remember,

is one of the four fundamental forces,

and it's the star of this part of the story.

As Newton showed,

gravity is more powerful where there is more stuff

and when things are closer together.

To give an example,

the gravitational pull of the Earth

is extremely powerful on you,

but if you move away out into space,

it suddenly gets much, much weaker.

So now let's move back to the early Universe

and think how this force might have worked.

Remember, there are some areas that are just slightly hotter

and slightly denser than others.

In those areas, gravity was just slightly more powerful.

So what it did was it clumped those areas together.

As they clumped together, they got denser,

so the power of gravity increased

and they began to clump even further together.

Gravity increases,

so the whole thing is clumping a bit like a runaway train.

Now, this gets faster and faster and faster.

And now what happens

is at the center of each of those clouds of atoms,

atoms begin to bang into each other

really violently,

and they begin to heat up, particularly at the center,

where there are the most atoms.

Now notice something.

So far our story has been about a Universe that's cooling down.

Suddenly, we're talking about an area of the Universe

that's beginning to heat up for the first time.

Eventually, the temperature reaches about 3,000 degrees.

Now, that temperature should sound familiar.

It's the temperature at which atoms

can't hold together anymore,

because protons can't hold on to electrons.

So what happens is you recreate

the sort of plasma that existed before the creation

of the cosmic background radiation.

Now, the temperature in the cloud keeps rising

until eventually, it reaches 10 million degrees.

And something spectacular happens at that temperature.

Protons start banging together so violently

that they overcome the repulsion of their positive charges,

and they fuse together, and are now held together

by the "strong nuclear force."

As that happens, there is a huge release of energy

as some of their matter is turned into pure energy.

This is very similar to what happens in an H-bomb.

So now, at the center of the cloud,

we have a sort of furnace

that's pushing back against the force of gravity

and that stabilizes the whole thing.

And now what's happened

is a star has lit up.

And that star is going to shine

for millions or billions of years.

We've now crossed our second major threshold

of complexity in this course.

From about 200 million years after the Big Bang,

the Universe starts filling up with stars--

billions and billions and billions of them.

And the Universe is now a much more interesting place.

Instead of the sort of uniform mush that we saw

before the appearance of the first stars,

we now have a Universe that's filled with stars.

It's not just that it's more interesting

to look at, stars are much more important than that.

Our Universe is filled with these sort of

glowing batteries that emanate light and heat.

It's a much more interesting place.

In fact, astronomers can see stars still forming today;

it's a process that's still going on.

They find them in star nurseries.

They're some of the most beautiful places

you can see in the heavens.

And, in fact, it's worth going onto the Hubble website

or looking through a telescope at some of these star nurseries

because they are amongst the most beautiful sights

you can see in the sky.

Stars increased the complexity of the Universe in another way.

They gave it new types of structure

at many different scales--

from the level of the stars themselves

to galaxies, to superclusters.

So let me try and describe these structures one by one.

Let's begin with the stars.

Stars themselves have a very clear structure.

At the center, you've got protons

that are at an extremely high temperature, as we've seen,

and they're fusing to form helium nuclei.

Just around the center, around the core,

you have a sort of store of protons

ready to be fused eventually when they sink down

into the center.

Now, photons of energy and light from the center

slowly work their way through the plasma,

taking sometimes thousands of years,

until eventually they reach the surface

and then they flash out into space.

So stars have a lot of structure,

but stars themselves

are gathered together by gravity into a much larger structure.

We call these galaxies.

Our Milky Way is our galaxy.

It contains perhaps 100 billion, some say 200 billion, stars.

It's absolutely huge.

And there may be 100 billion galaxies

in the entire Universe.

But structures exist at even larger scales too.

Gravity gathers galaxies together

into what are called clusters.

Our local group is a cluster like that.

It contains about 30 galaxies, including Andromeda

and the Magellanic Clouds,

both of which you can see with the naked eye.

Gravity can even hold clusters together

to form what are called superclusters.

These scatter through the Universe

in huge webs and sort of chains.

But beyond that, gravity is too weak

to hold superclusters together.

And it's beyond the level of superclusters

that you begin to see finally what Hubble saw.

You begin to see whole superclusters

moving apart, and there, at that scale,

you can see the expansion of the Universe.

Now, let's summarize.

We'll see throughout this course

that complexity builds on complexity.

Now we've got stars, and stars are going to be the key

to later forms of complexity.

Most of the Universe was then, and still is,

cold, dark, empty,

and from our perspective, very, very boring indeed.

But with stars, you have something

like campfires in Antarctica:

lights that light up a cold Universe.

And we'll see that from now on,

the Goldilocks conditions for further complexity

are to be found, not throughout the whole Universe,

but in galaxies, and above all, around the stars,

those cold campfires.

That's where our story is going to go now.