Welcome back to Cosmos in a Pod, Space,
and Astronomy series, episode 14.
Today, we're going deep, deep into the Milky Way galaxy,
our cosmic home.
That's right.
We'll be journeying through billions of years
from the Milky Way's formation to its ultimate fate,
uncovering fascinating facts
and some mind-blowing concepts along the way.
It'll be a wild ride.
Buckle up. Yeah.
Okay, let's rewind all the way back to the Big Bang,
roughly 13.8 billion years ago.
Yeah.
Where does the story of the Milky Way even begin?
So it all starts with these tiny fluctuations,
little, little tiny fluctuations
in the density of dark matter and gas
just moments after the Big Bang.
Think of them like little seeds
scattered across the vastness of space.
Gravity gradually pulled these seeds together,
causing them to grow and merge,
eventually forming the first galaxies,
including our own Milky Way.
So from these tiny irregularities,
something as immense as the Milky Way emerged.
It's hard to wrap my head around that.
These early building blocks, what were they like?
Yeah, so these were proto-galaxies,
swirling clouds of mostly hydrogen and helium,
the leftover ingredients from the Big Bang.
Okay.
Imagine this cosmic dance
with these proto-galaxies constantly colliding and merging,
creating larger and more complex structures.
So the early universe was a pretty wild and chaotic place
with these proto-galaxies just bumping
and grinding into each other.
Yeah.
I'd imagine things were pretty hot and explosive back then.
Absolutely, you're right.
Within these proto-galaxies, the very first stars ignited.
These were the population thousand stars,
massive giants composed purely of hydrogen and helium.
These stars lived fast and died young,
ending their lives in spectacular supernova explosions.
Supernovae, I remember learning about those in school.
They're like cosmic fireworks, right?
But they're more than just pretty lights, aren't they?
Precisely.
Supernovae are essential for creating the elements
that make up, well, everything we know, including ourselves.
When these massive stars explode,
they forge heavier elements like carbon, oxygen, and iron
and scatter them across space.
These elements become the building blocks
for future generations of stars and planets
and ultimately life itself.
Wow, so we literally owe our existence
to those ancient exploding stars.
That's incredible.
Okay, so we had these mergers creating a larger galaxy,
but how did the Milky Way get its iconic spiral shape?
That's a great question.
About 10 billion years ago,
gravity and the spinning motion of all that gas and dust,
it caused the Milky Way to flatten out into a rotating disk.
Think of it like spinning pizza dough.
It spreads out and becomes thinner as it spins.
This disk is where the action is.
It's full of gas and dust,
the perfect ingredients for forming new stars,
including our own sun.
So the disk is like the bustling heart of the Milky Way,
a cosmic nursery for stars.
What about those mesmerizing spiral arms?
They're so prominent in images of spiral galaxies.
What even creates them?
Yeah, those spiral arms, they aren't fixed structures,
but rather waves of density
that move through the galaxy's disk.
Think of it like a traffic jam in space.
Okay.
As these waves pass through, they compress gas and dust,
triggering bursts of star formation.
This is why spiral arms appear so bright.
They're filled with young hot stars.
So it's not just a beautiful design,
it's a dynamic process
that's constantly shaping the galaxy.
That's fascinating.
Now, we can't forget about the central bulge,
that bright, dense region at the heart of the Milky Way.
What's happening in there?
The central bulge is like a time capsule,
home to some of the Milky Way's oldest stars,
formed early in the galaxy's history.
It's a dense and crowded region,
and at its very heart lies a monster.
Oh.
Supermassive black hole called Sagittarius A.
A black hole.
Now, that's what I call a plot twist.
Tell me more.
Sagittarius A is a gravitational giant
with a mass equivalent to about four million suns.
While we can't see it directly,
its immense gravity affects the motion of stars
and gas all around it.
So this invisible monster is essentially controlling
the galactic center,
pulling the strings of the entire region.
You got it.
Its influence is profound.
It plays a key role in the evolution
of the galaxy as a whole.
So we've got this bustling disk where stars are forming,
the majestic spiral arms,
and this enigmatic central bulge
with its supermassive black hole lurking within.
But the Milky Way doesn't stop there, does it?
There's more to explore beyond the disk, right?
You are absolutely right.
Surrounding the disk in the bulge
is a vast spherical region called the Galactic Halo.
It's like a giant invisible bubble
encompassing the entire Milky Way.
What's out there in this halo?
Is it just empty space?
No, not at all.
The halo is home to ancient stars,
some of the oldest in the Milky Way,
as well as globular clusters,
tightly packed groups of thousands
or even millions of stars.
Wow.
These objects provide valuable clues
about the galaxy's early history,
acting like cosmic fossils,
preserving remnants of the Milky Way's past.
So the halo is like a treasure trove of ancient relics,
offering glimpses into the Milky Way's
long and eventful history.
Now, I've heard about this concept of galactic cannibalism.
Is that something that the Milky Way has engaged in?
Indeed.
The Milky Way, it didn't reach its current size
by simply existing peacefully.
It has a history of merging with
and absorbing smaller galaxies over billions of years.
So the Milky Way has been on a cosmic shopping spree,
gobbling up its smaller neighbors.
You could say that.
And we can actually see evidence
of this galactic cannibalism
in the form of stellar streams.
These are long, ribbon-like trails of stars left behind
as dwarf galaxies are torn apart
by the Milky Way's gravity.
It's like the Milky Way leaves a trail of cosmic crumbs
behind after its galactic feast.
What about our galactic neighbors, the Magellanic Clouds?
Are they also destined to be consumed by the Milky Way?
That's a very real possibility.
The Magellanic Clouds,
they're currently orbiting the Milky Way,
but their fate is uncertain.
It's a cosmic dance with these gravitational forces at play,
potentially leading to their eventual merger
with our galaxy.
So the Milky Way might continue to grow and evolve,
adding to its already impressive collection
of stars and gas.
Okay, so let's recap.
We have this magnificent barred spiral galaxy
with its distinctive spiral arms,
the center bulge housing a supermassive black hole,
and this vast halo surrounding it all.
But where do we fit into this grand cosmic picture?
Where's our little solar system located
within this vast structure?
Our solar system resides in the Orion Arm,
a relatively minor spiral arm
located about 26,000 light years from the galactic center.
It's a relatively quiet and calm region,
which has been beneficial
for the development of life on Earth.
So we're tucked away in a peaceful corner of the Milky Way,
far from the chaos of the galactic center.
That's good to know.
Now, to put things into perspective,
how big is the Milky Way exactly?
The Milky Way is a true behemoth.
It spans about 100,000 light years in diameter.
To put that into perspective,
if you could travel at the speed of light,
it would still take you 100,000 years to cross our galaxy.
It contains hundreds of billions of stars.
Some estimates put it at its highest 400 billion,
along with countless planets, moons, asteroids,
and vast clouds of gas and dust.
Those numbers are mind-boggling.
It makes you realize just how small and insignificant we are
in the grand scheme of things.
So we're just one tiny planet orbiting one star
among hundreds of billions in this vast galaxy.
And the Milky Way itself is just one of countless galaxies
in the observable universe.
That's right.
It's a humbling realization
that puts our everyday worries into perspective.
Now let's talk about the Milky Way's ultimate fate.
What does the future hold for our galaxy?
In about 4.5 billion years,
the Milky Way is on a collision course
with our nearest major galactic neighbor,
the Andromeda Galaxy.
A galactic collision.
That sounds like something out of a science fiction movie.
It's certainly a dramatic event,
but it's not as catastrophic as you might imagine.
The distances between stars are so vast
that individual stars colliding is unlikely.
Instead, it'll be more of a galactic merger.
The gravitational forces will reshape both galaxies,
eventually creating a new, larger elliptical galaxy,
often nicknamed Milcomeda.
Milcomeda, I love it.
It's like a cosmic mashup,
the ultimate blend of two galaxies.
So the Milky Way, as we know it,
will cease to exist,
but it'll be reborn as part of this new giant galaxy.
It's a reminder that the universe
is constantly evolving and changing.
Exactly.
And this collision is just one chapter
in the Milky Way's long and eventful story.
Well, this deep dive has already been incredibly insightful.
We've journeyed through the Milky Way's formation,
explored its structure,
and even glimpsed its ultimate fate.
But I know there's still so much more to uncover.
Are there any lingering mysteries about the Milky Way
that scientists are still trying to solve?
Absolutely.
Despite all we've learned,
there are still many unanswered questions about our galaxy.
For example, we're still trying to understand
how Sagittarius A,
that supermassive black hole at the center,
actually formed.
Another big mystery is the nature of dark matter.
This mysterious substance seems to make up
a significant portion of the Milky Way's mass,
but we still don't know what it is.
So even with all our technological advancements,
the Milky Way still holds many secrets.
It seems like there's always more to learn and explore.
That's the beauty of science.
It's a continuous journey of discovery,
and the Milky Way is a vast and complex laboratory
full of wonders waiting to be revealed.
Well, this has been an absolutely mind-blowing start
to our deep dive into the Milky Way.
We've covered so much ground,
from the galaxy's formation
to its eventual merger with Andromeda.
Join us for part two of our Milky Way exploration,
where we'll delve into the mysteries of dark matter,
uncover the secrets of exoplanets,
and explore the ongoing research
that's pushing the boundaries of our understanding
of our cosmic home.
Until then, keep looking up
and never stop questioning the universe.
I'll see you there.
All right. Bye.
Bye.
Welcome back to our cosmic journey through the Milky Way.
Last time, we talked about the Milky Way's impressive size,
its dramatic history of galactic cannibalism,
and its future collision with Andromeda.
This time, we'll delve into some of the more mysterious
aspects of our galaxy, starting with dark matter.
You mentioned earlier that dark matter makes up
a significant portion of the Milky Way's mass,
but we can't see it or directly detect it.
It sounds like something straight out
of a science fiction novel.
It is.
It's one of the biggest mysteries in astrophysics.
It's fascinating and a little bit spooky
to think about all that unseen matter just out there.
So how do we even know it's there if we can't see it?
Well, we can infer its presence
through its gravitational effects.
So imagine you're watching a merry-go-round spinning.
OK.
You notice that the horses on the outer edge
are moving much faster than you'd expect,
based on the visible structure of the merry-go-round.
That would suggest there's some unseen mass,
some hidden force providing the extra gravity
to keep those horses from flying off.
That's a great analogy.
So we see stars and gas moving faster
than they should in galaxies, including the Milky Way,
indicating there's something massive out there that we can't see.
What could this mysterious dark matter be?
That's the million dollar question.
Scientists have proposed many theories.
Some believe it's made up of exotic particles,
unlike anything we've ever detected before.
Others propose it could be tiny black holes,
or other objects that don't emit light.
The search is ongoing, with experiments and observations
around the world and in space trying to unravel
the secrets of dark matter.
It's incredible to think that something so fundamental
to the universe remains such a mystery.
Speaking of mysteries, let's shift gears a bit
and talk about another fascinating topic.
Exoplanets.
These are planets that orbit stars outside our solar system,
and it seems like we're discovering new ones all the time.
How do we find these exoplanets, considering they're so far away
and often overshadowed by the brilliance of their host stars?
It's a remarkable feat of scientific ingenuity.
There are a couple of clutter methods.
One is called the transit method.
So imagine you're watching a distant star
and a planet passes in front of it,
blocking a tiny bit of its light.
We can detect this dip in brightness
and use it to infer the presence of a planet.
So it's like a miniature eclipse, but on a cosmic scale.
That's amazing.
Precisely.
Another method is called the radial velocity method.
As a planet orbits a star, its gravity tugs on the star,
causing it to wobble slightly.
We can detect this wobble by carefully measuring
the star's light spectrum, revealing the presence
of an unseen companion.
So by carefully observing the light from distant stars,
we can indirectly detect the presence
of planets orbiting them.
It's like deciphering a secret code hidden within starlight.
Exactly.
And these techniques have revealed a truly astonishing
diversity of exoplanets.
We've found gas giants larger than Jupiter,
rocky planets like Earth, and everything in between.
We've even found planets orbiting two stars,
like something out of Star Wars.
Wow.
That's incredible.
Makes you wonder what other strange and wonderful worlds
are out there waiting to be discovered.
Now back to the Milky Way.
How many exoplanets do we think are
out there in our own galaxy?
Based on our current understanding,
it's estimated that there could be more planets than stars
in the Milky Way.
So potentially hundreds of billions of planets
in our galaxy alone.
That's mind boggling.
Do we think any of these planets could be habitable,
like Earth?
That's a question that drives a lot of current research.
The search for habitable exoplanets
is one of the most exciting areas of astronomy.
We're looking for planets in the habitable zone
of their stars, the region where conditions might be just right
for liquid water to exist on the surface, which
is considered a key ingredient for life as we know it.
It's thrilling to think that there could be other worlds out
there with oceans, continents, and maybe even
some form of life.
It makes you feel a little less alone in the vastness of space.
It certainly does.
The possibility of finding life beyond Earth
is one of the most profound questions
humanity has ever asked.
This deep dive into the Milky Way has been incredible.
It's humbling to learn about the sheer scale and complexity
of our galaxy, and to realize how much
we still don't know.
But as you said earlier, that's the beauty of science.
It's a journey of discovery.
And the Milky Way provides an endless frontier
for exploration.
Join us for the final part of our Milky Way deep dive,
where we'll discuss some of the ongoing research
and future missions that are poised
to revolutionize our understanding
of our cosmic home.
Until then, keep looking up and never stop
questioning the universe.
Welcome back to the final part of our deep dive
into the Milky Way.
We've explored the galaxy's dramatic history,
uncovered the mysteries of dark matter and exoplanets,
and contemplated the Milky Way's eventual merger
with Andromeda.
Now let's turn our attention to the present and future.
What are some of the ongoing research efforts and missions
that are expanding our understanding
of this incredible galaxy we call home?
Well, there are so many exciting projects underway.
One that stands out is the Gaia mission,
a space observatory launched by the European Space Agency.
It's creating a 3D map of the Milky Way
by measuring the positions, distances, and motions
of over a billion stars.
A billion stars?
That's an astronomical amount of data.
How does Gaia even begin to collect all that information?
Gaia is equipped with incredibly precise instruments
that allow it to pinpoint the locations and movements
of stars with remarkable accuracy.
It's like having a cosmic GPS, mapping out the stars
with incredible detail.
That's incredible feat of engineering.
What kind of insights are we gaining from all this data?
Gaia's data is revolutionizing our understanding
of the Milky Way's structure, evolution, and history.
We're learning about stellar streams,
those remnants of ancient galactic mergers,
and gaining a clearer picture of how dark matter is distributed
throughout the galaxy.
So it's like piecing together a giant cosmic puzzle,
revealing the intricate workings of the Milky Way.
You mentioned earlier that scientists are still
trying to understand the nature of dark matter.
Are there any missions specifically focused
on solving that mystery?
There are many experiments around the world
and in space dedicated to detecting and characterizing
dark matter particles.
These experiments use a variety of techniques
to try to capture these elusive particles,
hoping to shed light on their properties and origins.
It's like a cosmic detective story,
with scientists searching for clues
to unlock the secrets of this invisible substance that
permeates the universe.
Now, I can't let you go without asking about the James Webb
Space Telescope.
It's been making headlines with its stunning images
of distant galaxies.
What role is it playing in our understanding of the Milky Way?
The James Webb Space Telescope is a game changer
for astronomy.
It's powerful.
Its powerful infrared capabilities
allow it to see through dust clouds,
revealing hidden regions of star formation within the Milky
Way.
It's also providing us with unprecedented views
of the galactic center, giving us
a closer look at the supermassive black hole lurking
there.
Wow, it's amazing to think that we can now
observe these cosmic phenomena with such clarity.
With all these incredible missions and research efforts,
it seems like we're entering a golden age of astronomy.
Absolutely.
We're living in an exciting time for anyone
who's ever looked up at the night sky
and wondered about our place in the cosmos.
With each new discovery, we're gaining a deeper understanding
of the Milky Way, our cosmic home.
This deep dive has been an incredible journey.
It's reminded me of the vastness and beauty of the universe
and the importance of continuing to explore and ask questions.
Thank you for joining us on this cosmic adventure.
We hope you've enjoyed exploring the Milky Way with us.
And remember, the universe is full of wonders
waiting to be discovered.
So keep looking up, stay curious,
and don't forget to follow and subscribe to Cosmos
and a pod for more explorations of the universe.