When you think about the North Pole, you
don't expect it to go anywhere. And you
certainly don't expect it to change
places with the South Pole. That would
just be wrong. Our magnetic compasses
would all point the wrong way. We'd need
to update our maps. Birds would probably
be horribly confused. And yet, although
they sound like something out of science
fiction, geomagnetic reversals like this
are real. They've happened before. and
the process behind it might be a lot
more dangerous than you'd think. To be
clear, it's not the reversals themselves
that are potentially dangerous. It's the
buildup. During those times, the Earth's
magnetic field, the shield around our
planet that keeps us safe from deadly
solar radiation, will drop to as low as
10% of its current strength, leading one
group of scientists in 2021 to predict
climate shifts and mass extinctions. And
others to describe satellites being
destroyed, electrical grids going
offline, and deadly radiation raining
down on us for hundreds or even
thousands of years.
This is troubling when you consider that
we are a couple of hundred thousand
years overdue for our next geomagnetic
reversal. And based on fluctuations in
the Earth's magnetic field that
scientists are detecting right now, the
buildup to a geomagnetic reversal may
even have begun already,
which begs the question, should we be
worried?
I'm Alex Mccoan and you're watching
Astramm. Join with me today as we
explore the science behind geomagnetic
reversals and find out whether the next
one will be an apocalyptic scenario or
whether it'll lead to nothing more than
a few lost birds. What truly happens
when things go south?
Let's start by trying to understand
where the Earth's magnetic field comes
from in the first place.
It's not a given that our planet would
have a magnetic field. The two planets
flanking us, Mars and Venus, do not have
one. And yet, the Earth does, which is a
good thing, as without one, there is a
very real chance life would not have
been able to arise here in the first
place.
Thanks to the protective cocoon of this
field, deadly solar radiation is
deflected away from the planet's
surface, allowing things to flourish
without all that radiation breaking down
our DNA, causing mutations and cancers.
Scientists are still trying to figure
out all the particulars of why certain
planets have fields and certain others
don't. But the current leading theory is
that the Earth's core acts as a giant
dynamo.
It's a principle of physics that you can
use electrical fields to create magnetic
ones and vice versa. This is the
principle that power plants work under.
Moving a magnet through a coil of wires
causes electrical current to start to
flow as that changing magnetic field
exerts a force on the electrons present
there. But similarly, the motion of
electrons creates a magnetic field to
form imperpendicular circles around the
direction of motion in accordance with
Faraday's law of induction.
But the way this applies to the Earth's
core is a delicate complicated process.
To start with, our core needs to be at
least partially liquid, which
fortunately is true.
Above the solid inner core that lies at
the heart of our planet is a liquid
outer core, where the pressure isn't
quite high enough to keep things in a
solid state. It's very hot in the outer
core, though, 6,000° C at its warmest
point. so hot that it rivals the surface
temperature of the sun, which when
combined with the lower pressure
compared to the inner core, is more than
enough to keep the iron and nickel that
makes it up flowing down there.
The temperature drops as you move away
from the center of the Earth. This gets
circulation going. Hot conductive
material from the warmer deeper regions
of the outer core rises, then cools,
then falls again, creating loops and
currents of flowing material. Our
electrical field starts to be generated.
But if there are many of these flowing
loops, which in theory there would be,
why does Earth only have one north pole
and one south pole? Surely the created
magnetic fields would be all over the
place.
Well, there is thought to be an extra
force at play that takes all these
fields and unifies them, pointing them
in the same direction. This force is
thought to be the corololis effect.
Dynamo theory states that the corololis
effect causes these flows of iron to not
rise and fall as straight lines, but as
spirals.
The spinning of the earth causes them to
gently be spun in turn, creating giant
springs.
As each segment of each spring is
creating a magnetic field in a circle
around it, the net result is that the
inside of these springs creates a solid
unified field that all moves in the same
direction upwards, while the outside
brings that magnetic field looping back
down again and back in to the bottom of
the coil. In short, it creates the
well-known magnetic dipole north and
south that we see today.
However, if there's anything that you
should take away from this, it's that
this process is precarious as it is
based on a lot of liquid iron
essentially just slloshing around which
is not very consistent. Our magnetic
field thus has little fluctuations and
wobbles all the time. We see this in
different ways, but a big one is that
our north pole is constantly moving.
Since scientists began keeping track of
it in 1831, the North Pole has gradually
shifted about 1,100 km, leaving its
original location in Canada and moving
up towards Siberia. Its rate of motion
is also increasing, going from 16 km a
year to roughly 55 km a year. A big
jump.
This might still be akin to just the
momentary wobbles of a spinning top,
though. Yes, it deviates somewhat, but
it always remains roughly upright.
That's a far cry from a complete
reversal.
However, scientists are certain that
such reversals have happened before.
They even have a specific number,
183 times in the last 83 million years.
How do they know? The answer lies locked
in our Earth's surface iron.
When magma erupts from the Earth's
mantle, it can contain small amounts of
iron. As these can move freely in the
molten magma, they tend to orient
themselves in the direction of the
Earth's magnetic field. However,
scientists noticed that there were
layers of geological history where the
iron was pointing one way and layers
where it was pointing in the reverse
direction. Their explanation, the entire
pole of the planet had flipped.
On average, these flips seem to happen
every 450,000 years, although the last
few have only got 300,000year gaps
between them. Comparatively, it's been
750,000
years since the last reversal. You might
think that we're overdue for one, and
some have made that claim. However,
scientists have found that there's
little rhyme or reason to the timing of
these flips. One of the longest gaps
between flips took place in the
Cretaceous period and it lasted 40
million years. The record holder, the
Kman reverse supercron, was 312 to 262
million years ago, 50 million years with
no reversal.
Scientists are still trying to
understand what causes these flips.
However, the current theory is that
something, perhaps some interplay
between the mantle and the outer core
causes a fluctuation in the core
spinning. This disrupts the spiraling
shapes of the core's flow, breaking them
down. The magnetic field of the Earth
stops being unified and generally
becomes a sprawling mess, fighting
against itself. Several poles might
temporarily arise during this period of
shifting magnetic confusion. While in
time things settle down and the spirals
reassert themselves, it seems random as
to which way they will do this. Meaning
about half the time our magnetic north
pole reappears over the geographical
south. This reasserting can take 1,000
to 10,000 years.
All right, but would that really be the
end of the world? Why does this matter?
Well, during that period before the
poles reassert themselves, our Earth's
magnetic field drops to as low as 10% of
its current strength. In theory, this
could leave us much more vulnerable to
all the solar radiation space throws at
us. We could see auroras reaching much
further south during that time. Skin
cancer rates would increase. Our
satellites would find themselves with
not enough shielding. Radiation would
fry their circuits, causing them to
malfunction, shut down, and potentially
even slowly fall from orbit.
Our electrical grid would be much more
vulnerable to solar storms, which could
lead to large segments of the Earth's
population without power. With no
electricity or satellite communication,
it would be a devastating blow to our
global civilization.
It could be worse than that. A research
team from the University of New South
Wales in Sydney even linked one of the
most recent weakenings of the magnetic
field, the Lashamps event, a temporary
800year wobble rather than a full flip
to megapornal mass extinctions in
Australia, including the deaths of
Droaton,
giant Australian wombats, and Procopadon
Goliath, giant kangaroos.
Temporary wobbles like this are known as
geomagnetic excursions rather than full
reversals and they happen over much
shorter time frames. Their transition
periods can last as little as 200 years
rather than 10,000 which can be much
more difficult for species to adapt to.
In their 2021 study, they argued that
there was a spike in atmospheric
radiocarbon levels caused by the
collapse of the Earth's magnetic field,
indicating climate shifts that could
have led to these extinctions. The
timing lines up uncomfortably.
But how real are these risks? Honestly,
it's a mixed bag. A point in our favor
is that other than this recent study,
there is no indication that magnetic
field reversals have ever coincided with
mass extinction events. It seems like
many reversals have come and gone
without affecting animal or plant life
at all. And even in this study, such
mass extinctions seem to have been
limited in scope. There is no claim from
the researchers that this was a global
phenomenon. Other parts of the world
remained unaffected even during the
Lashamps event.
It seems that a perfect storm might have
been in play where specific conditions
over Australia left it more vulnerable
to solar radiation.
In terms of our global society, it's
worth noting that these magnetic changes
would take many lifetimes to complete,
even at their fastest. This would be
slow enough that we could come to terms
with our new reality. If our satellites
don't have enough shielding, we would
have time to build some that were better
protected. If solar radiation becomes a
larger risk, we could remain indoors
more, sun cream might become more
powerful to mitigate the dangers of
cancers if not remove them entirely.
And according to NASA, even if our field
were to significantly weaken, it's not
like we would be left without
protection. Our atmosphere itself can
catch radiation, meaning that we would
remain safe from solar winds and cosmic
radiation, at least to some degree. It
would take far longer than 10,000 years
for our atmosphere's ozone to be
stripped away. But I would be surprised
if there wasn't at least some turmoil,
at least while we adjusted to living
under a reduced magnetic field. Big
changes to how a society operates are
always painful. And this isn't entirely
hypothetical. Did you know the Earth's
magnetic field has been steadily
weakening for the last 200 years? It
would take another 1,300 years for it to
vanish completely. So, there's plenty of
time for it to stop its current downward
trend. And there's no reason to think
this isn't just a temporary wobble. But
on top of that, there is also the South
Atlantic anomaly to consider. A section
of the Earth's magnetic field that is
already showing signs of significant
weakening that covers most of the space
around South America and the neighboring
ocean.
This zone might not influence life on
the ground, but is dangerous enough that
it has fried satellites and threatened
astronauts. A Hubble telescope has to
turn itself off every time it flies
through it. Imagine that. But across the
entire globe, that's what we might
expect while the poles are reversing.
Concerningly, the South Atlantic anomaly
has been growing continuously since we
started keeping track of it, possibly
suggesting the approach of either
another geomagnetic wobble like the
Lashamps event or that a full-blown
reversal is already upon us. If it
happens, it won't likely be something
that ends civilization as we know it.
But if the study about Australian
megapora is correct, it isn't going to
be without impact either. species could
die. Humans will have to accommodate a
very different, more hazardous space
environment.
It's interesting to learn about
geomagnetic reversals and their
potential impacts on the planet. But
while we are not likely to see one
happen in our lifetimes, for the
generations of humanity after us, this
might turn out to be a lot less
hypothetical. They might be seeing it
firsthand.
Think you know Jupiter? Think again. For
decades, scientists argued over what the
core of our biggest gas giant was like.
Was it solid or missing altogether? Then
in 2017, NASA's Juno mission made that
debate irrelevant overnight. The data
from Juno suggested both sides were
wrong and revealed a third option no one
expected. Jupiter's core isn't solid,
but it isn't absent either. It's fuzzy.
And that's a problem because it upends
everything we thought we knew about
Jupiter's formation, its interior, and
even its bizarre magnetic field.
I'm Alex Mccoan and you're watching
Astramm. Join me today as we uncover
exactly what Juno found. Explore how a
fuzzy core could form in the first place
and reveal why this changes how we think
not just about Jupiter, but gas giant
planets everywhere.
For decades, two competing theories
dominated the scientific conversation
around Jupiter's core. Many supported
the gravitational collapse theory which
suggests that Jupiter formed directly
from the collapse of a gas cloud under
its own gravity. This would have
happened in the colder outer reaches of
the solar system before Jupiter migrated
to its current location. In this
scenario, the gas giant would have no
core at all. It would simply be a layer
cake of churning gas all the way
through. But this theory didn't have the
whole scientific community convinced.
Others were almost certain Jupiter's
core was solid, made up of heavy
elements like carbon, nitrogen, oxygen,
magnesium, silicon, and iron. As this
solid core grew larger and larger, its
gravity started capturing more hydrogen
and helium, swirling it together over
millions of years to form the planet we
all recognize today. Intuitively, this
seems to make sense. Our solar system
formation models suggest giant planets
could be created this way since ice and
rock would condense first in the outer
solar nebula, capturing gases in their
gravity as they migrated inward. This
theory, known as the core accretion
model, predicted a dense, well-defined
core with a clear boundary separating
the compact center from the surrounding
layers of gas. To resolve the debate,
early missions to Jupiter all took their
turn trying to discern what lies beneath
the red giant's dramatic atmosphere. By
the 1990s, scientists knew that Jupiter
was rich in heavy elements, implying the
planet was made of more than just
hydrogen and helium. The Galileo mission
also found evidence that Jupiter's
magnetic field must somehow be generated
by liquid metallic hydrogen in its
interior. But if the core is purely
liquid, how did Jupiter form in the
first place? The standard theory of
planetary formation requires a solid
nucleus to start gas capture. If Jupiter
once had such a core but somehow lost
it, how did that happen? Could
everything we know about how gas giants
form be completely misguided?
Despite the successful missions to
Jupiter, the planet structure remained a
mystery. The data gathered wasn't
precise enough to determine whether its
core was solid or diffuse, what it's
made of, or how exactly it generates
such a massive magnetic field. But that
all changed with Juno.
On the 5th of August 2011, NASA's Juno
mission launched from Cape Canaveral in
Florida. Its main objective was to get
closer to the truth of Jupiter's
composition by measuring its
gravitational and magnetic fields with
unprecedented precision. Unlike Galileo,
Juno was purpose-built to map the
planet's gravitational field in great
detail, about 100 times better than
previous maps. When it entered orbit on
the 4th of July 2016, it began tracing a
highly elliptical polar orbit swooping
down within just 4,200 km of Jupiter's
cloud tops. It did this again and again
from several angles, a path that made
this probe incredibly sensitive to tiny
changes in Jupiter's gravity.
But why are we interested in gravity in
the first place? What does that have to
do with figuring out what Jupiter's core
is made of? Well, we've all seen gravity
depicted like this, a perfectly round
cone, the same on all sides. I'm sorry
to tell you, this diagram is a bit of an
oversimplification.
For a planet's gravity to be completely
uniform like this, the distribution of
mass inside it would also have to be
perfectly uniform. In reality, if you
zoom in really close, their
gravitational fields look a little more
like this. Planets are made up of many
different elements and materials, each
with their own masses, densities, and
distributions. These differences are
reflected as tiny, almost imperceptible
variations in a planet's gravitational
field. That's why Earth's gravitational
field is actually slightly different
over mountains than planes and why
scientists are so fixated on mapping
Jupiter's gravitational field with
incredible precision.
As Jupiter's gravity fluctuates, it
causes Juno to speed up or slow down.
The spacecraft is so precise, it can
detect changes in speed as subtle as
0.01
mm/s.
At the same time, Juno is continuously
beaming a steady radio signal back to
Earth, which scientists can decode using
the Doppler effect, where gravity is
stronger, Juno accelerates, and we
perceive a higher frequency wave, while
a deceleration due to weaker gravity
would result in a lower frequency wave.
By repeating this over and over,
scientists can build up a very precise
map of Jupiter's gravitational field,
which directly reflects how its mass is
arranged inside.
While the Galileo mission managed to
paint Jupiter's gravity in very broad
strokes, Juno brought it into razor
sharp focus. And what it revealed about
Jupiter's core caught researchers by
surprise. Turns out both theories about
Jupiter's core were wrong. It seems to
have a core, but it isn't solid like we
thought. It's fuzzy. Instead of a dense,
compact ball, it's dilute, gradually
blending with the hydrogen-rich layers
above it. It doesn't appear to have any
sharp boundaries. It's also much wider
than expected, spanning about half the
radius of Jupiter itself.
The findings quickly sparked a flurry of
questions, including whether our
understanding of how Jupiter formed
needed a refresh in light of this
exciting new data from Juno.
A popular theory soon emerged to explain
this unexpected discovery that Jupiter
once had a solid core to begin with, but
a catastrophic collision in its early
history shattered and scrambled it in
with the surrounding lighter gases to
give us the fuzzy core we see today.
The only problem is our standard model
for how giant planets like Jupiter form
doesn't work without a solid core. So
either Jupiter's fuzziness somehow
developed later on or our models are
wrong. Anyway, for such a dramatic
shattering to occur, the collision must
have been massive, possibly with another
young planet. Scientists speculate that
up to half of Jupiter's core could have
originated from the remains of this
planet. It was a neat enough theory
except for one unexpected hiccup.
A curious team of researchers tried to
model this giant collision using a
supercomput. They wanted to emulate the
exact event that would lead to the
results Juno showed us. So they designed
several possible scenarios of a massive
object colliding with a Jupiterized
planet and ran multiple simulations
varying the size of the Jupiter
protolanet and the angle and speed of
collision. But try as they might, they
couldn't find an event that led to the
fuzzy core Juno showed us. Every time
they tried, the models did the same
thing. The impact would initially rock
the planet to its core, but after a
while, the dense rocky material would
settle back down again, like sediment at
the bottom of a glass. It didn't
dissolve into the rest of the planet. A
sharp boundary would reappear, clearly
separating the core from the outer
hydrogen layers. It didn't fit the Juno
data. So, it was back to the drawing
board.
funnily enough, the next clue in this
puzzle didn't come from Jupiter at all.
It came from its next door neighbor.
Well, that is if you consider 648
million km away next door. We've known
since 2014 that the waves in Saturn's
rings are caused by vibrations inside
the planet. This gives us an insight
into what the planet's core might look
like, similar to how earthquakes let us
study Earth's interior. When researchers
paired Cassini's gravitational field
data with these wave measurements, it
painted a staggering picture. These
observations show that at least some of
Saturn's deep interior doesn't convect.
This is a big deal. Inside a giant
planet like Saturn, heat is constantly
trying to escape. Normally, that happens
through convection. It's what is
constantly happening in Earth's mantle
or when you heat up a soup. Hot fluids
rise to the surface, cool, and then fall
back down, only to be heated up and rise
again. On and on it goes. If Saturn were
fully convective, it would mix heavy
elements throughout its interior. There
wouldn't be a dense central region at
all. The whole thing would be a fully
mixed, homogeneous soup. But if it were
partly stable against convection, we'd
expect to see a gradient of material
with heavier elements concentrated
towards the center and tapering outward.
And that's exactly what the data shows.
Researchers published their findings in
2021, arguing that the only way to
explain Saturn's ring wave data,
gravitational field data, and partial
lack of convection is that it too has a
fuzzy core.
As it happens, Juno data also suggests
large regions of Jupiter may not be
convective. We seem to be slowly
connecting the dots. If Saturn and
Jupiter have fuzzy cores, they likely
stem from a common denominator rather
than a random collision event. Now
scientists are working on a new emerging
theory of how the gas giants came to be.
One in which fuzzy cores are a natural
part of planetary formation. We haven't
arrived at a neat explanation yet. But
it is clear that the old assumptions we
had about the largest planets in our
solar system are incorrect.
Jupiter and Saturn are not made up of
solid core and gas envelope. nor do they
have a completely mixed interior. Their
fuzzy cores are made up of a
compositional gradient with more heavy
elements concentrated in the center
which dissolve out into the gas envelope
without a clear boundary.
This complexity and uneven mixing
challenges our current models for
planetary evolution. Where our old
simplistic model predicted the giants
would cool predictably over time, these
new models don't follow the same
patterns. And the same is true for all
the gas giant exoplanets we've
discovered and studied so far. But in
the meantime, there is one other jigsaw
piece that needs to fit the puzzle
created by Jupiter's fuzzy core. its
weird and wacky magnetic field.
For years, scientists have known that
Jupiter's magnetic field is generated
through a dynamo process in its metallic
hydrogen layer. This layer spans 20 to
60,000 km deep where temperatures can
exceed 30,000 Kelvin and pressures are
millions of degrees greater than on
Earth's surface. Under these extreme
conditions, hydrogen is in a liquid
state. But even more incredibly here,
hydrogen's electrons become deoized or
free flowing. This creates an
electrically conductive metallic state.
Coupled with Jupiter's fast rotation,
this metallic liquid hydrogen creates a
dynamo effect. Though the exact process
of how it's powered remains a mystery.
Whatever it's doing, it's working.
Jupiter has the largest, strongest
magnetic field of any planet in the
whole solar system. Its magnetosphere
spread 7 to 21 times the diameter of
Jupiter, tapering into a tadpole shape
behind it that extends into Saturn's
orbit about 1 billion km away. However,
Jupiter's magnetic field also has some
quirky characteristics. It's much
stronger in the northern hemisphere than
the southern hemisphere. has intense
localized magnetic spots and two
magnetic south poles.
Scientists hoped Jupiter's fuzzy core
might actually explain some of these
strange behaviors. Frustratingly for
them, the opposite turned out to be
true. Jupiter's fuzzy core actually
complicates rather than explains its
magnetic field. Magnetic fields in
planets are usually created by swirling
motions of electrically conducting
material like the metallic liquid
hydrogen in Jupiter's core. However,
Juno data showed that large regions of
Jupiter like Saturn seem to be at least
partially non-convective.
Researchers modeled the fluid dynamics
of Jupiter's interior in two potentially
non-convective regions to see how they
would affect the magnetic field. one in
the upper part of the planet's interior
and the other lower down corresponding
to the dilute core. They concluded that
the upper stable layer helps explain
Jupiter's magnetic field even better
than previous solid core models.
However, the lower region representing
the non-convective dilute core did not
explain Jupiter's magnetic field on its
own. In other words, a completely stable
fuzzy core produces a magnetic field
that's very different from the one we
actually observe. Now, researchers
believe Jupiter's dynamo is more
complicated than originally thought.
It's possible that below the uppermost
molecular hydrogen layer, Jupiter has a
layer of helium which rains down through
the liquid hydrogen like oil passing
through water. Some think this could
have an effect on the magnetic field.
Another theory claims Jupiter's dynamo
doesn't operate in a homogeneous way
like it does on Earth and that instead
the planet's lopsided magnetosphere is
the result of variations in density,
electroconductivity,
or both. But on the whole, no one knows
exactly how this magnetic field is
produced or what role the fuzzy core
plays in its creation.
One thing we do know for certain though
is Jupiter's magnetic field is
responsible for the biggest, brightest
auroras in the solar system. On Earth,
auroras are only visible for a 4 to 6
month window. On Jupiter, they never
stop, covering the poles with a dazzling
display of color, hundreds of times more
powerful and energetic than the auroras
we're familiar with. By stringing
together far UV images from Hubble's
imaging spectrograph, scientists were
able to create these videos of the
auroras in action. Aren't they
spectacular?
Despite Juno's discoveries, Jupiter
keeps its secrets close to its chest. We
still don't know how its fuzzy core
actually formed, nor do we know how
permanent it is. Is the fuzzy core a
stable structure that will endure for
billions of years? Or is it slowly
dissolving into Jupiter's gaseous
layers? What relation does it have to
the metallic hydrogen above it? And the
resulting magnetic field Juno mapped off
as he caused just a natural part of gas
giant formation. We can't say for
certain yet, but one thing's for sure.
Our current models don't show the full
picture. Hopefully with further study,
we'll slowly be able to answer these
questions one by one. Though the more we
learn, the more questions we'll keep
asking. The pursuit of truth is
relentless, and it is also perhaps the
most human thing we can do.
Imagine standing on a quiet hill,
watching the sky burst into a symphony
of colors as the sun peaks above the
horizon. It's a daily spectacle that
many of us take for granted. The warm
hues of orange, red, and pink splashing
across the sky. Yet, this beautiful
sunrise is only the final chapter in the
light's long journey. If we trace the
path of these photons from their end
point in the retina at the back of your
eye through the Earth's atmosphere
across the 150 million km void
separating our planet from its host star
and finally through the varied and
tumultuous layers of that star. We
discover the source of the warmth on
your face and the colors painted across
the sky. The sun's core, a nuclear
engine that has been raging for 4 and a
half billion years. Born in a cosmic
nursery from the remnants of ancient
stars, the glowing sphere of searing
plasma that dominates our sky is the
product of complex forces that have
played out over millennia.
So, let's take a journey back in time,
tracing the origins of the sun,
exploring its intricate layers, and
mapping the elements that make up its
very structure. I'm Alex Mccoan, and
you're watching Astramm. Join me as we
dive into the depths of our sun and
learn what secrets lie behind the
blinding curtain of light and time.
To understand how the sun formed, we
must go back to before our solar system
even existed. About 4.6 billion years
ago. At that time, in a relatively quiet
region of the Milky Way galaxy, a
massive cloud of gas and dust known as a
giant molecular cloud drifted silently
through space. This was no ordinary
cloud. It was immense, possibly spanning
hundreds of light years across with a
mass equivalent to millions of suns.
Within this cloud lay the scattered
remnants of ancient stars that had long
since exhausted their nuclear fuel and
exploded as supernova, casting their
enriched contents into the cosmos. This
stellar debris included a mix of
elements such as hydrogen and helium,
the building blocks of stars along with
heavier elements like carbon, oxygen,
nitrogen, and iron.
The presence of these elements made this
molecular cloud fertile ground for
forming new stars and planetary systems.
However, such a massive cloud requires a
trigger to initiate the cascading
collapse that results in stellar birth.
Scientists believe that this trigger
could have been a shock wave from a
nearby supernova explosion that
compressed parts of the cloud, causing
it to fragment and collapse into regions
of higher density. This collapse marked
the beginning of the pre-olar nebula,
the dense region within the molecular
cloud that would eventually give birth
to our solar system. Some scientists
have even proposed a name for this
hypothetical exploding star, Kowati
Quay. Named after the Aztec goddess of
Earth and fertility, Kati Quay
symbolizes the death and rebirth cycle
where, in this case, the death of one
star conceded the formation of new ones.
As the gravitational collapse of the
giant molecular cloud progressed, it did
not result in a single massive object,
but rather fragmented into multiple
dense clumps. This fragmentation occurs
due to a phenomenon known as genes
instability, named after the British
physicist Sir James Jeans. The genes
length is a critical distance within a
cloud at which the forces of gravity are
balanced with the natural internal gas
pressure that keeps the cloud propped
up. When a defined section of the cloud
exceeds the gene's length, it will
collapse in on itself. Different regions
within the molecular cloud exceed this
genes length at different times due to
variations in density and temperature.
As these regions become gravitationally
unstable, they collapse independently to
form multiple protostellar cores as
opposed to one single massive body.
The protostellar core was the earliest
phase in our sun's life that was
recognizably starlike, crunching itself
into a tighter and tighter sphere by the
ever clenching fist of its own gravity.
The core is surrounded by infalling gas
and dust. As more material accumulates,
the core becomes denser and hotter,
setting the stage for the next phase of
star formation, the protostar.
Once a protostellar core becomes
sufficiently dense and hot, it evolves
into a protostar. The central region has
heated up to the point that it begins to
emit light and heat from the energy
released by gravitational contraction.
But its core has yet to reach the
temperatures required to ignite nuclear
fusion in the core. As the protoar
continues to accumulate material and
grow in mass, the pressure and
temperature in its core increase
dramatically. Our sun developed through
this embryionic state of contraction and
heating for millions of years before
eventually building up its core
temperature to about 10 million° C at
which point hydrogen nuclei began to
fuse into helium. And with that the sun
was born.
At this stage the innate angular
momentum of the surrounding material
that shrouds the infant star generates
rotation. A cloud of this size will
always have some slight rotation.
Nothing in the universe is still. And
conservation of angular momentum
dictates that the cloud must spin faster
and faster as it crunches down into
tighter space, similar to how a spinning
figure skater speeds up as they tuck in
their arms.
Around the equator of rotation, some of
the material is moving fast enough to
stay in orbit. But higher up and lower
down, the momentum is insufficient to
resist the protostar's ravenous pull and
falls helplessly into its jaws. And so
the cloud flattens out into a disc, a
protolanetary disc. This disc is a
cosmic lottery. As it cools and
coaleses, planets, moons, asteroids, and
comets will be relentlessly created and
destroyed. Some material will be robbed
of its momentum and tumble into the sun,
while neighboring matter will go on to
become part of the many bodies that make
up our solar system today.
With its new ability to fuse hydrogen
atoms into helium, the sun could finally
generate energy to push back against the
forces of gravity that sought to squeeze
it further. The energy streaming out of
the fusion reactions created an outward
radiation pressure that balanced the
inward gravitational pull of the gas,
allowing the young star to achieve a
stable state known as hydrostatic
equilibrium. In this state, the star no
longer contracts under its own gravity
and it enters a stable phase of its life
known as the main sequence. This
balancing act between internal pressure
pushing outward and gravity crushing in
is the axis that defines every stage of
the sun and all stars lives. We saw it
during the initial collapse and here as
it settles into a stable main sequence
star and it will be the pendulum that
eventually swings towards its dramatic
death. For now, let's unpick the process
of nuclear fusion and how it's capable
of keeping an object as massive as the
sun stable and steady for billions of
years.
To understand how nuclear fusion occurs
in the sun, we need to examine extreme
conditions present within its core.
Today, temperatures reach around 15
million°
and pressures more than 250
billion times that of the Earth's
atmosphere. In this blazing cauldron,
hydrogen atoms are stripped of their
electrons, forming a plasma composed of
free protons and electrons.
Under such intense conditions, these
protons, normally repelled by their
shared positive electric charges, are
forced into extremely close proximity.
The force that usually keeps them apart
is the culum force, an electrostatic
repulsion between positively charged
particles. It's exactly the same force
that resists as you try to push the same
ends of a bar magnet together.
Overcoming this force is the primary
challenge for nuclear fusion to occur.
Despite the extreme kinetic energy of
protons in the sun's core, most
collisions are still not energetic
enough to overcome the coolum barrier,
under normal conditions, protons need
immense energy to get close enough for
the strong nuclear force to bind them
together. This barrier is so significant
that physicists around the early 1920s
using a classical understanding of how
particles interact with each other
determined that fusion should not occur
at the temperatures and pressures found
in the sun's core. To solve the puzzle,
we needed a scientific model that has
come to explain many of the seemingly
impossible phenomena we observe in the
universe. Quantum mechanics.
The quantum mechanics revolution of the
1920s introduced the concept of
particles behaving both as particles and
as waves. One of these phenomena is
quantum tunneling where particles have a
certain probability of tunneling through
a barrier even when they lack the
classical energy needed to overcome it.
In the sun's core, quantum tunneling
allows a small fraction of protons to
effectively bypass the coolum barrier
without having to climb over it. In the
classical sense, even though these
protons do not have enough kinetic
energy to overcome the electrostatic
repulsion directly, quantum mechanics
gives them a chance to appear on the
other side of the barrier. To visualize
this process, consider a diagram of the
coolum barrier. In the diagram, you will
see a high energy barrier representing
the repulsive electrostatic force
between two protons at varying
distances. The energy needed to climb
over this barrier is represented as a
peak. The calculations of a classical
physicist would require the sun to have
temperatures high in the billions of
degrees C, thousands and thousands of
times higher than the sun's core to
hurdle this barrier. But quantum
mechanics allows for the probability
wave of a proton to tunnel through this
barrier, appearing on the other side
without ever going over the peak. This
tunneling effect is what enables fusion
to occur in stars like the sun despite
the seemingly insurmountable coolum
barrier. Once a proton has tunnneled
through the koolum barrier, it gets
close enough to another proton for the
strong nuclear force to take over. The
strong nuclear force which is far more
powerful than the kulum force operates
only at very short ranges on the order
of phentometers where one phento is
equal to 10 ^ -15 m roughly the size of
a single proton. The strong nuclear
force binds the protons together. But
this is only the first step in a series
of nuclear events known as the proton
proton chain.
The proton proton chain reaction is the
dominant fusion pathway in the sun and
other stars of similar size accounting
for roughly 99% of the sun's energy
production.
It starts with two free roaming protons
combining to form dutyium, a heavy
isotope of hydrogen along with the
emission of a positron and a nutrino.
This step is rare but essential as it
allows the fusion process to continue.
The dutarium then rapidly fuses with
another proton to form helium 3,
releasing a high energy photon, a gamma
ray. In the final step, two helium free
nuclei collide and fuse to form helium
4, releasing two protons and a
significant amount of energy in the form
of radiation.
While the proton proton chain is the
dominant fusion process in the sun,
there is another pathway at play
particularly in stars hotter and more
massive than our sun. This pathway is
known as the CN O cycle, short for
carbon, nitrogen, oxygen. In this cycle,
carbon, nitrogen, and oxygen nuclei act
as catalysts to fuse protons into
helium. The CNO cycle is more efficient
at higher temperatures and only
contributes a small percentage of our
sun's energy output. The energy produced
in these fusion reactions comes from a
small amount of mass being converted
into energy as described by Einstein's
famous equation E= MC².
In the fusion process, the mass of the
resulting helium 4 nucleus is slightly
less than the combined mass of the
original four protons. This missing mass
is not lost, but rather converted into
energy that radiates outward from the
sun. Every second, the sun converts
about 4.3
million tons of its mass into energy.
That's right. The sun is losing mass all
the time. To put this into perspective,
this is the equivalent of the mass of
about 3 million cars being turned into
pure energy every second. This is the
energy that ultimately powers the sun
and provides the light and heat that
reaches Earth.
But before these photons pouring out of
these reactions can reach the Earth and
everything else in the solar system and
beyond, they must first escape the
700,000 km of chaotic solar interior
that lies above them. To truly grasp the
complexity of the sun and its stratified
layers, let's follow a single photon, a
particle of light, from its creation
within a proton proton reaction all the
way to the surface. This journey is
anything but straightforward. In fact,
it will take thousands, if not hundreds
of thousands of years, for this photon
to complete its journey, passing through
several distinct layers of the sun, each
with their own unique properties and
behaviors.
As we've already found out, our photon's
journey starts in the core, a region
that spans about 25% of the sun's
radius, but holds nearly half of its
total mass. And as we've also heard, the
core is incredibly dense at around 160 g
per cubic cm. It's over 20 times denser
than iron. To put that into perspective,
if your phone was made of material that
dense, it would weigh as much as a
heavyduty sledgehammer
for our photon. This means that the
environment is so tightly packed with
particles, it cannot travel far before
being absorbed by a neighboring
particle. Of course, not long later,
that particle will pack the photons's
bags and send it out into the merely of
the core for another particle to catch
and release in some other random
direction. It's a bit like trying to
navigate through a dense crowd where
every few steps you bump into someone
and have to change direction.
This constant interaction of absorption
and remission is what gives the core its
chaotic nature, resulting in a journey
for a photon that is more of a random
walk than a direct path outward. This
random movement of photons is
reminiscent of Brownian motion where
particles suspended in a fluid move
erratically due to collisions with
smaller fastoving molecules. And there
is no preference for the direction that
a photon could fly back out of a
particle that had just absorbed it. In
theory, a photon could make it all the
way to the surface of the sun before
random chance directs it back towards
the core. To add to the complexity, as
photons are continuously absorbed and
remitted, the energy gradually decreases
from gamma rays to x-rays and eventually
to visible light as they move towards
the sun's outer layers.
Understanding the processes occurring
within the sun's core has been a
challenging endeavor for astronomers.
The core is completely obscured by the
outer layers of the sun, meaning we
cannot directly observe it through any
form of light. Instead, scientists have
developed ingenious methods to infer the
dynamics of the roaring inferno below.
One of the key techniques is the study
of helioismology,
the observation of waves rippling across
the sun's surface. Just like
seismologists study earthquakes to
understand Earth's interior,
heliocismologists measure the vibrations
of the sun's surface caused by sound
waves that travel through its interior.
These sound waves are influenced by the
temperature, density, and composition of
the sun's layers, allowing scientists to
construct models of what is happening
deep within.
Solar nutrinos, elusive subatomic
particles that I've talked about in a
previous video, are also released during
the fusion reactions in the sun's core.
Nutrinos interact so weakly with matter
that they can travel straight out of the
sun in just 2 seconds, hardly aware of
the tangle their photon counterparts are
caught up in. For decades, solar nutrino
detectors on Earth measured fewer
nutrinos than predicted by theoretical
models, leading to what was known as the
solar neutrino problem.
It wasn't until scientists discovered
that nutrinos change their properties or
flavors on their journey to Earth that
the mystery was resolved, confirming
both our understanding of particle
physics and the nuclear processes in the
sun's core. Next, the photon enters the
radiative zone, which extends from the
edge of the core to about 70% of the
sun's radius. Here, temperatures
gradually drop from 15 million° to
around 2 million° C. The density of
matter also drops, going from around the
density of gold in the zone's depths to
less than water near the top. The
dominant energy transportation method is
still this frenetic process of photons
skittering through the layer, carrying
their energy on average towards the
surface. And as the density of the
plasma continues to decrease as we move
outward, our photon has slightly more
wiggle room capable of bigger leaps
between interactions. But even here
outside of the core, the sun's material
is still so opaque that even a few
centimeters could block out as much
light as hundreds of meters of water. We
are able to envision such precise models
of the sun's interior because of models
like the standard solar model or SSM. It
is a mathematical framework based on the
principles of hydrostatic equilibrium,
energy conservation, and radiative
transfer. Essentially using our
understanding of how materials and
fluids behave here in our laboratories
on Earth to infer the properties of a
place out of our reach. The SSM models
how energy is passed between particles
in its complex equations, describing how
photons are transported through the
dense plasma. This allows us to
calculate how transparent the solar
material is to radiation at different
temperatures and densities. And from
there we can work out where the
radiative zone ends and the next layer
begins.
This is one of my favorite things about
mathematics. It allows us to explore
environments that we can never visit.
Almost like how quantum tunneling allows
protons to jump over the coolum barrier
and produce the photons we are now
following.
As our photon approaches the upper
boundary of the radiative zone, it
enters the tacoline, a thin transitional
layer where the radiative zone meets the
next layer, the convective zone. The
tacoline is an environment of extreme
contrast where the relative uniformity
of the radiative zone meets the boiling
bubbling convective zone.
The strange conditions in this extremely
thin layer likely plays a key role in
the solar dynamo that generates the
sun's magnetic field. The tacoline is
thought to twist and amplify the
magnetic field, shaping the sunspots and
solar flares that define the star
surface.
Zipping through the thin taco, our
photon arrives at the convective zone.
Stretching out from about 70% of the
sun's radius to just beneath the visible
surface, the photosphere, the
temperatures have dropped to below 2
million°.
Now, the sun's plasma is no longer dense
enough to effectively transfer energy by
radiation. Instead, the plasma becomes
unstable and begins to move in massive
convection currents much like boiling
water in a pot. Hot plasma rises towards
the surface in large cells called
granules. These granules with diameters
of thousands of kilometers surge upward
under their power of buoyancy at speeds
of hundreds of meters/s like a beach
ball that you force below the water
rushing to the surface as it squirms
from under you. The force required to
move this volume of matter against the
sun's gravity is astonishing. Imagine
the force of 10 billion hurricanes and
you'd be just starting to get close to
the energy necessary. This convective
process moves energy much more
efficiently than the radiative zone,
creating turbulent rolling waves of
plasma that churn vigorously.
I have explained these convection cells
and the beautiful hypnotic patterns they
create on the sun's surface in a lot of
detail in this previous video.
This is a significant change in how
energy is transported. While photons
still interact with particles, the
primary mechanism of energy transfer in
the convective zone is no longer the
random absorption and reimission between
particles, known as radiative diffusion,
but rather the movement of hot plasma
rising and cooler plasma sinking. This
convection motion carries the energy
outward more efficiently than in the
radiative zone.
Upon reaching the top of the convective
zone, the photon is carried to the
photosphere, the sun's visible surface.
Temperatures have now cooled to about
5,500°,
and the plasma has thinned enough for
photons to escape without being
constantly reabsorbed. It is from this
thin, roughly 500 km deep layer that the
light we see from the sun is emitted.
Above them lies only the sun's corona
which is itself a fascinating
environment but only around a billionth
of the density of the photosphere and
therefore not much of an obstacle to our
photon. It is incredible with an object
like the sun that many refer to as a
ball of gas can have such a sharp
boundary. But the photosphere is where
our photon finally breaks free,
traveling at the speed of light and
beginning its journey across the
vastness of space.
Our nutrino friend that was created at
the same time, it's long out of the
Milky Way by now.
Since settling into its stable main
sequence phase, nuclear fusion has
altered the strength of the sun's
layers, gradually increasing its
brightness over billions of years. This
is because the fusion process inevitably
leads to changes in the composition,
density, and temperature of the sun's
core, which in turn affects the overall
behavior, and the future of our star.
As hydrogen fuses into helium, hydrogen
gradually depletes in the core and
helium ash begins to build up. Unlike
hydrogen, which readily underos fusion
at the sun's current core temperatures,
helium requires much higher temperatures
to fuse. As the abundance of helium
increases, the core becomes denser.
Helium nuclei are more massive than
hydrogen nuclei. And as more helium
collects in the core, the overall
density increases. At the same time,
because helium is not fusing and
creating energy, it does not contribute
to the outward radiation pressure that
counterbalances the sun's immense
gravitational pull. The result is that
gravity will begin to dominate, causing
the core to contract further.
To prevent collapse under its own
gravity, the sun must increase its core
temperature as helium builds up. The
hotter core turns up the dial on
hydrogen fusion because nuclear fusion
rates are extremely sensitive to changes
in temperature. This increase in fusion
releases more energy, which results in a
brighter star and temporarily restores
the balance between gravity and
radiation pressure. Through this
process, the sun's energy output has
increased by about 30% over its
lifetime. And this trend will continue
for billions of years as long as
hydrogen fusion dominates in the core.
In the radiative zone, the layers have
grown hotter and more opaque. The rising
temperature of the core means more
energetic photons are produced, which
are more prone to interacting with the
surrounding plasma and pinballing
around. As a result, this zone has
become less efficient at radiating
energy outward, trapping photons for
longer before they can continue their
escape. The convective zone has also
expanded slightly over time due to the
increased energy production.
As the sun continues to burn through its
hydrogen fuel over the next 5 billion
years, its core will eventually be left
overburdened with inert helium that can
no longer sustain fusion under its own
pressure. When this happens, the sun
will evolve into a red giant,
dramatically expanding and engulfing its
inner planets, including Mercury and
Venus and possibly the Earth. In this
phase, the core will contract and heat
up until it ignites in a helium flash,
starting the fusion of helium into
heavier elements like carbon and oxygen.
Yet again, swinging the pendulum between
the relentless gravitational hammering
and the resisting forces of energy from
the core. This process will create new
layers and cause the sun to swell even
further before shedding its outer layers
to form a ghostly remnant, a planetary
nebula. The core that remains will cool
and fade, becoming a white dwarf, a
dense earthsized ember of a once raging
fire.
This transformation from a stable star
to a red giant and eventually a white
dwarf is a remarkable and complex
process with many fascinating details
which we will no doubt explore in a
future video.
But ending our journey from the depths
of the sun's ancient past to its modern
interior, let's return to that quiet
hill where we began, watching the colors
of sunrise. I hope the next sunrise you
see becomes that little bit more
special. I hope the pink and orange
photons scattered for one final time on
the molecules of Earth's atmosphere
before streaming through your pupils
will make you think of the incredible
voyage they have endured. Beginning with
a collapse of a colossal cosmic cloud
into an elementb building furnace,
struggling for hundreds of thousands of
years through a melting pot of plasma to
gift you with this beautiful scene. I
hope this exploration has deepened your
appreciation for that daily miracle we
often take for granted. And there's
still so much more to uncover about our
closest star, from the formations it
will undergo to the profound impacts it
will have on our solar systems future.
Thank you for joining me on this journey
through space and time. If you found
this journey as enlightening as our
hosts are, please give the video a like
and fuse it with your own thoughts down
in the comments below. Thanks for
watching.
The universe is full of secrets and some
of the most incredible ones are hiding
just beyond the reach of visible light.
What if I told you that more than 1.5
billion unseen objects from galaxies and
newborn stars to some of the oldest
stars in our entire galaxy are sitting
just out of reach of us cloaked in
cosmic dust.
That's a little frustrating to think
about, isn't it? Until now. That is
because thanks to the European Southern
Observatory's visible and infrared
survey telescope for astronomy, better
known as VISTA, we can finally lift the
veil on these hidden wonders.
For the first time in human history, we
have a pretty comprehensive infrared map
of the Milky Way. one that pierces
through the obscuring fog of space to
reveal an unprecedented view of our
galaxy and what lies beyond.
I'm Alex Mccoan and you're watching
Astramm. Join me today as we appreciate
how this firstofits-kind map was made
and take a look at some stunning images
that reveal previously unknown stars
across our galaxy.
In September 2024, VISTA published the
largest and most detailed infrared
survey of the Milky Way ever undertaken,
encompassing a 13-year period from 2010
to 2023 across 140 nights of
observation. This project has captured
around 200,000 images and generated 500
terabytes of data.
That's the same amount of data as it
would take to stream a 4K video for
nearly 3 years straight. VISTA is part
of ISO's Paranal Observatory located in
Chile with its main focus being to map
large areas of the sky
using Vista's infrared camera. known as
Veram. The team was able to peer through
the dust and gas that permeates our
galaxy and uncover some of the Milky
Way's most hidden places.
Traditional telescopes allow us to view
space in visible wavelengths, which
range between about 380 to 700 nanome.
But VISTA isn't like traditional
telescopes.
Instead of relying on visible light
alone, Vista operates at infrared
wavelengths between 900 and 1,200
nanometers, allowing it to detect
otherwise invisible objects like stars
obscured by dust and called brown
dwarfs, also known as failed stars,
which don't emit enough visible light to
be seen with a traditional telescope.
To get an idea of the difference between
visible and infrared light, take a look
at these two images of the Lobster
Nebula or NGC 6357.
One taken in visible light and the other
with Vista's telescope. We can see that
in the infrared, the dust that obscures
our field of view seems to disappear,
revealing what look like hundreds of
thousands or maybe even millions of
previously invisible stars.
The map was created through Vista
variables in the Via Lakia or VVV
survey. Via Lakia being the Latin name
for the Milky Way and its companion
project, the VVV extended survey or
VVVX.
The data collected from these two
companion projects that make up the
Vista Infrared Survey have already led
to the publication of more than 300
scientific articles.
Unlike other recent space maps, this is
one of the most detailed ones ever made.
It's the first infrared survey to cover
nearly 80% of the Milky Way's luminous
mass and provides the largest infrared
catalog ever made of our galaxy's
central region. It allows astronomers to
study our galaxy in finer detail than
ever before. This survey gives us an
accurate 3D view of the inner regions of
the Milky Way which were previously
hidden by dust. It covers an area of the
sky equivalent to 8,600
full moons and contains about 10 times
more objects than any previously
published infrared map from 2012.
Our Milky Way consists of a central
bulge, a dense, bright, puffed up
collection of stars with a flat disc of
two spiral arms wrapping from the ends.
This image shows the area of our galaxy
that was mapped in the survey. The red
squares mark the central regions of the
galaxy which were observed by the
original survey and then reobserved
again by the extended survey. And the
other square colors show areas that were
only observed as part of the extended
survey. From this image, you can see
that these surveys have focused right on
the central plane of our galaxy,
spanning part of the disc and most of
the nuclear bulge. But what has Vista
revealed?
Argentinian astrophysicist Dante Maniti,
who led the survey project, said, "We've
made so many discoveries, we have
changed the view of our galaxy forever."
And as much as I'd love to talk about
all of them in this video, it's probably
best I stick to some of the highlights.
As part of the survey in 2015, Vista
turned its attention to the star
formation region of Messia 20, also
known as the Trifford Nebula, which lies
about 9,000 lighty years from Earth.
Viewed in visible light in this image,
we can see a beautiful nebula glowing
pink from the emission of ionized
hydrogen and surrounded by a blue haze
of scattered light from young hot stars.
The cloud of gas and dust is obscuring
the star-filled space behind it. Now
look at this second image taken by
Vista's infrared camera.
Peering beyond the clouds reveals a
whole swarm of new stars.
This image not only allows us to see
through the Triid Nebula, but by chance
it revealed objects on the far side of
our galaxy that had never been seen
before. To their surprise, astronomers
identified two faint reened objects as
seafed variable stars. While they appear
in the image to be just behind the edge
of the triid nebula, in reality they are
very distant about seven times farther
than the nebula that once helped to
block them from our view. Seeed
variables are a type of bright star that
is unstable. They brighten and fade over
a period of a few days or a few months
depending on their brightness.
The first variable star we ever
identified in modern times was Omreon
seti also known as mirror. It had been
described as a nova until 1638 when
Johanna's Halwoods observed it getting
brighter and dimmer in a cycle that
lasted 11 months. As for this pair of
newly discovered stars, they are the
only seafed variables that we have
identified so far in this location which
lies beyond the central bulge on the far
side of our galaxy. And they can be
really useful too. You can think of them
as a kind of cosmic yard stick that can
be used up to distances of tens of
millions of light years. If you know how
long the stars pulsation period from
bright to dim is, then you can infer its
absolute brightness as well as its age,
you can compare absolute brightness to
the apparent brightness, that is the
amount of light that reaches Earth. So
you have a measure of how distant the
star is. With a few reference points
like these, we can build up a real
picture of the scale of our galaxy and
beyond.
Looking toward the galactic center, a
team of astronomers and data scientists
found even more candidate seed stars,
655
in fact. They then sorted these into one
of two classes, and found that 35 of
these 655 stars were classical seafs,
the younger of the two. This was really
exciting, especially since the galactic
bulge was thought to contain mostly
elderly stars that are at least 8
billion years old.
Recording their pulsation periods, the
team revealed that all 35 of these seeds
were less than 100 million years old and
some of them may be as young as 25
million years old. To put that in
context, our own son is about 4.5
billion years old. So, the youngest
seafooded has only been around for 0.6%
of our son's lifespan.
The team's exploration of seafoods
culminated in another major discovery.
By mapping the 35 classical seafoods
they found, the team was able to trace a
completely new feature in the Milky Way.
A thin disc of young stars that
stretches right across the galactic
bulge.
buried behind thick clouds. It had
remained unknown in all previous surveys
of the region. In revealing this
structure combined with the discovery of
all the seafoods as I mentioned earlier,
scientists have inferred that there has
been continuous star formation along the
midplane of the galaxy for the past 100
million years. There might also be even
younger seaw feeds that we haven't seen
yet as these stars would be so bright
that they would be saturated in the VV
survey. The fact that we found this thin
disc of young stars within the galactic
bulge is incredible.
We used to think that the galactic bulge
was an ancient feature of our galaxy's
past where exclusively old stars had
formed separately from the stellar disc.
But this finding reveals that things
aren't so black and white and that the
formation of newer stars within the
bulge could be a natural progression of
our galaxy's evolution.
But even more inspiring perhaps is a
discovery by the Vista Infrared Survey
that lies at the ancient heart of our
Milky Way galaxy.
In 2016, for the first time, a type of
ancient star known as Ryre,
another variable star was discovered in
the center of the Milky Way galaxy by a
team led by astrophysicist Dante Maniti
and Rodrigo Andreas Ramos. This type of
star is usually found in globular
clusters, which tend to orbit the outer
regions of the galaxy. A globular
cluster is a tightly packed group of
stars that contains tens of thousands to
millions of stars bound together by
gravity. They're also really ancient,
containing a stellar population that can
be over 10 billion years old. The team
found 12 R Lray stars during the VVV
survey, which suggests that they might
be the remnants of an ancient globular
cluster right at the heart of our
galaxy. This finding also provides
evidence that might help astronomers to
decide between the two competing
theories of how nuclear bulges form.
While some scientists think that the
nuclear bulge forms early in the
galaxy's evolution when multiple smaller
galaxies violently collide, others say
that it forms gradually over time where
gas is funneled inwards to trigger star
formation.
Finding these ancient stars here
suggests that the bulging center of the
Milky Way likely grew through the
merging of primordial globular clusters,
therefore supporting the first theory.
So, not only does it hint at our own
galaxy's beginnings, but it also offers
compelling evidence into how these
galactic bulges might form in other
similar galaxies.
Speaking of ancient stars, Vista was
able to find two new globular clusters
as part of the infrared survey in 2011.
In this visible light image, a known
globular cluster UKS1 can be seen on the
right as a hazy red splotch. This
cluster had been the dimst known
globular cluster until the new
discoveries.
Now compare this same patch of sky, but
this time in vista's infrared light.
Suddenly, we can see what we have been
missing. much more faint than the known
UKS1. We can make out a second globular
cluster, this time in the upper left of
the image, which has been named VVV
CL001.
Another globular cluster, aptly named VV
CL00002,
was found soon after, and this small
faint group of stars may be the closest
known globular cluster to the center of
the Milky Way. Did you know that there
were only 158 known globular clusters in
the Milky Way before these new ones were
found by Vista?
For the survey to identify two more of
these rare stellar objects is quite a
significant accomplishment.
Within this central region of the
galaxy, it's easy for younger stars and
cosmic dust to obscure globular
clusters, especially since their age
prevents them from shining as brightly.
But now that they've been revealed,
these features bring exciting
possibilities for further study. It
could just be an illusion of
perspective. But scientists have
wondered whether VVV CL001 is
gravitationally bound to UKS1.
If this is the case, then they would be
the Milky Way's first known binary
globular cluster pair. We found binary
clusters in other galaxies like in
Centurus A and the large Magelanic
cloud, but scientists think it might be
when these gravitationally bound
clusters collide that we get the most
massive globular clusters like Omega
Centuri.
So studying a binary cluster right in
our own galaxy could produce some
amazing insights into this process. It's
all speculation at the moment, but it's
definitely cool to think about.
In addition to globular clusters, the
VISTA infrared survey identified a
multitude of other types of star
clusters. At least 96 new open or
galactic clusters have been found, which
typically contain fewer, younger stars
and are much more common than the
globular type. Like the globular
clusters, they have been hidden by
cosmic dust. But VISTA's 4.1 m infrared
telescope has lifted the curtain to show
them in all their glory. Take a look at
just a few of these stunning images we
now have of these objects.
One of these open clusters, VV VVV
CL00003,
is much more difficult to make out in
images compared to the tightly packed
globular clusters. Try and see the
density differences in the stars in this
section of the image compared to the
surrounding regions.
It was found by Vista 15,000 lightyear
beyond the Milky Way center and also
happens to be the first of its kind to
be discovered on the far side of the
galaxy.
The sheer scale of this survey is
staggering. Covering a vast region of
the sky and mapping more than 1.5
billion objects, this data has already
led to fascinating discoveries that are
rewriting our understanding of the Milky
Way and beyond. And that's just the tip
of the iceberg. This survey will serve
as a foundation for future telescopes
and observations, which will hopefully
be able to expand on Vista's legacy with
even higher resolution and sensitivity.
We now have the most detailed 3D map
that has ever been made of the Milky Way
structure and objects, one that unveiled
hidden wonders previously beyond our
reach. And scientists are already
uncovering new galactic features and
reshaping our understanding of the
galaxy. With the information from this
groundbreaking infrared survey, as well
as the recent work from ISSa's GIA
mission in visible light, it's an
exciting time to be an astronomer, and
we can expect a flurry of new insights
about our own galaxy and the universe as
a whole. VISTA's infrared observations
have unveiled dozens of hidden star
clusters and millions of previously
unseen stars. They have revealed new
stellar nurseries where stars are born
and they have broadened our
understanding of the formation of our
Milky Way.
Looking at the sky through different
wavelengths has brought about a new era
of galactic exploration, and I can't
wait to see what else astronomers and
data scientists are going to uncover
thanks to Vista's 3D map.
I'm going to preface this video by
saying the universe is a very weird
place for us simple mortals.
Our lifespans are just a blink of an eye
compared to the age of the universe. And
things we expect to be constant like
space and time behave very differently
from what you may initially expect. So
keep this in mind throughout the video.
To answer the question of where the Big
Bang originated, I'm going to have to
provide some context. The leading theory
regarding the beginning of the universe
is the Big Bang theory. And without
going into all the complicated details,
I'll summarize it like this. About 13.7
billion years ago, everything that is in
the universe today was crammed together
into a space the effective size of zero.
At the very beginning, not even atoms
existed. It was just a hot and dense
soup of fundamental particles.
Since the beginning, the universe has
expanded rapidly. As it expanded and
cooled, atoms formed and stars were
born.
Now, the universe's expansion combined
with the constant speed of light has
turned the universe into a time machine.
If we look at any region of space, we
don't see galaxies as they are, but as
they were.
Galaxies we see in the foreground are
much more developed, forming the more
elegant and defined shapes you see here.
That is because we are seeing these
galaxies as they were only millions of
years ago. They've had billions of years
to form since the start of the universe,
and so they look much more mature and
developed.
On the other hand, as we look at more
and more distant galaxies, these
galaxies appear younger.
Galaxies that are billions of light
years away appear as they would have
shortly after the Big Bang because the
light emitted by them has taken that
long to get to us. They look misshapen
and there is a lot of star formation
going on within them. But in reality,
it's important to remember that these
galaxies are just as old as ours, and
they no longer occupy the location where
we can see them. They are probably much
further away now because of the
expansion of the universe.
It is also important to realize that
there is no center of the universe or
conversely that everywhere is the center
of the universe because it doesn't
matter where you are here or a billion
lighty years away everything is
expanding away from you. Everything is
expanding away from everything.
Just as a side note though, gravity
combats the effects of the universe
expanding. That's why superclusters of
galaxies exist
and the universe has a filamentary
structure.
The gravity from galaxies is attempting
to keep clumps of them together even
though the expansion of the universe is
also pulling them apart.
What you end up with are filaments with
empty bubbles or voids in between that
will only get bigger as the universe
expands further.
You may have heard of the term the
Hubble constant. This is how fast the
universe is expanding. Currently thought
to be around 80,000 km/h per million
lighty years. So for a section of space
1 million lighty years across, it
expands by 80,000 km every hour.
A section 100 million lightyear across
would expand by 8 million km every hour.
The current value of Hubble's constant
implies that the entire universe is
expanding faster than the speed of
light. Meaning there is a sphere around
us that we will not be able to see
beyond.
Past this sphere, galaxies are moving
away from us faster than the speed of
light. Meaning light emitted by them can
never reach us.
Everything within this sphere is the
observable universe. Another term you've
probably heard before, we can't see or
detect anything beyond the observable
universe, which is why we don't know if
the universe is infinite or finite.
Even if it is finite, it couldn't have
an edge and would have to loop around
because, well, the universe is just
that. Everything that exists, what would
be beyond the edge of the universe
otherwise?
So, we want to know where the Big Bang
originated. Where in the night sky do
astronomers look to see where the
universe started?
Well, the answer is everywhere.
Because the universe always has been the
whole universe. It has just changed in
size from being very small to very big.
It doesn't have specific coordinates
because it is an explosion of the
coordinate system itself.
And this is what shortly after the Big
Bang looked like, albeit in microwaves.
This is what we call cosmic microwave
background radiation. And you can see it
anywhere you look into space, assuming
you have a space telescope that can
detect microwaves because Earth's
atmosphere is really good at blocking
microwave radiation.
350,000 years after the Big Bang, the
universe was hot. around 2,500°
C.
Even though this heat would have emitted
visible light, we can't see it because
the expansion of the universe has
stretched the wavelengths of
electromagnetic radiation by a factor of
1,000. Meaning the photons no longer
arrive at Earth as visible light, but
rather as microwaves.
So, just like seeing those distant
galaxies billions of light years away
using visible light,
we can see what the universe looked like
before galaxies even existed by
observing these microwaves.
This makes this image effectively the
oldest thing we have ever seen.
Fascinatingly, the slight variations in
the image are the precursors to the
filamentary structure of the universe
you've seen earlier in the video.
We are quite lucky in that there are not
really any bright sources of microwaves
in the universe apart from the cosmic
microwave background radiation, which
means this view is a relatively
uncontaminated view of the universe
350,000 years after the Big Bang. Can we
see beyond that? No, not really.
Before that, atoms were just becoming a
thing and light couldn't travel through
the soup of fundamental particles.
So, the center of the universe is
everywhere and nowhere in particular.
Look at any part of space with a
microwave telescope and you're
effectively looking at shortly after the
Big Bang. Like I said, the universe is
weird.
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