When 15 supernova go off close together,
both in time and proximity, it makes
quite a bang. It should be of no
surprise that such a violent event
should fundamentally transform the
region of space around where it
occurred. Interstellar dust was swept
aside from the forces of those
concurrent blasts, creating a monumental
void of low density matter and a shock
wave that continues to hurtle across the
galaxy to this day at a rate of 6 km a
second. In its wake, plasma reaching 1
million° C in temperature. This
simultaneous Swiss cheesing and heating
up of the interstellar medium is what is
now called a hot bubble and represents
both the end of stars and their
beginning. But this is not some distant
structure that lurks in a far away
corner of the universe. Our solar system
isn't even heading right towards it. We
are in it charging for its point of
origin head first.
Welcome to our local hot bubble. What
scientists now realize is the local
environment that exists around our solar
system. It is a neighborhood we are
still exploring, but its nature is
becoming clearer and clearer. So, what
do we know about the local hot bubble?
How did it form? And what more is there
to be discovered?
I'm Alex Mccoan and you're watching
Astramm. Join me today as we walk in the
aftermath of exploding stars and discuss
how scientists even determined we were
in the heart of a cataclysm to begin
with.
The local hot bubble was not always
something we knew about. First
identified in the 1970s from
observations of low energy X-ray
emissions that were detected over the
entire sky, the local hot bubble was
hypothesized to be a large cavity in the
interstellar medium called a superbubble
filled with tenuous million degree low
density gas. In the 1990s, scientists
found that X-ray emissions could happen
anywhere neutral atoms interacted with
the solar wind. challenging the idea
that the emissions must point to a large
hot bubble. But soon evidence would
reveal that the hypothesis from decades
earlier was indeed correct.
In 2014, NASA confirmed the existence of
the LHB through the diffuse X-ray
emission from the local galaxy mission
known as DXL.
While soft background radiation can come
from other sources like from comets for
example, the mission found that only 40%
of the fog of low energy X-rays came
from within our solar system. This
affirmed that the dominant source was
diffuse X-ray emissions emanating from
the million degree region of
interstellar plasma known as the LHB.
Although this confirmed the bubble,
questions remained about what could
create such a massive void and what
might explain the thousands of
surrounding young stars. The prevailing
answer proved to be both violent and
fascinating.
Recent research suggests that the local
hot bubble was the aftermath of around
15 supernova explosions that occurred
sequentially within a span of a few
million years. erupting in relatively
close proximity to one another.
Scientists estimated that the first of
these massive stellar explosions went
off roughly 14 million years ago, each
expelling enormous amounts of energy,
pushing out the surrounding interstellar
material and heating the remaining gas
to extreme temperatures. Evidence of
these ancient explosions has been
preserved in our Earth's geological
record in deep sea sediment deposits in
the form of a special isotope called
iron 60. This radioactive isotope can
come from a few different sources, but
the most common source of iron 60 is
believed to be supernova explosions.
We know that the source of the isotope
is extraterrestrial because the earth
itself has no way of producing iron 60
on its own and matching deposits have
been found on the moon as well. The
reason that this radioactive isotope is
special is because we know how long its
half-life is. We know that it decays
into cobalt 60, another radioactive
isotope, before it finally decays into
nickel 60, a stable element.
Iron 60 has a halflife of 2.6 million
years and cobalt 60 has a fairly short
halflife of just 5.3 years. Because of
this, when we find a deposit that
contains these elements, scientists can
compare the amounts of iron 60, cobalt
60, and nickel 60 like an elemental
clock to reveal when that material was
deposited on our planet. And luckily for
us, international research teams have
found several such deposits over the
last couple of decades.
In 2016, iron 60 deposits were found in
deep sea crust samples taken from the
Pacific, Indian, and Atlantic oceans,
indicating two distinct spikes in the
radioactive debris that pointed to
several supernova events in the
notsodistant past. And not too far from
our solar system, just 326
light years away, the sample showed a
spike of iron 60 between 3.2 and 1.7
million years ago, and another spike
between 6.5 and 8.7 million years ago.
Nuclear physicist Anton Walner, who led
one of these research teams studying the
deposits, said that the fact that the
more recent debris was spread across 1.5
million years, suggests that there were
a series of supernova that occurred one
after another in close succession.
Astrophysicist Dieter Breitvert who led
a second team of scientists identified a
likely source of these supernova
explosions which would have occurred 196
to 423 lighty years from the sun. These
supernova that created our local hot
bubble may have been part of an aging
star cluster whose surviving members are
now associated with the Scorpius Centura
stellar group. Using the iron 60
deposits, the team was able to trace the
signals of two supernova, one that
happened 1.5 million years ago and the
other 2.3 million years ago as the
result of the deaths of stars that were
8.8 times and 9.2 times the mass of our
sun, respectively.
In fact, our LHB is still growing today,
albeit much more slowly than when the
supernova exploded millions of years
ago. The speed of expansion has
plateaued at about 6 km/s. Now,
according to astrophysicist Katherine
Zucker, in 2022, Zucker authored a
groundbreaking paper that reconstructed
the evolution of our galactic
neighborhood, tracing the chain of
events that created our local hot bubble
and led to the formation of all the
young stars we see nearby today. From
there, they made an incredible
discovery.
Using data from the European Space Ay's
Gaia telescope, Zucker and her team were
able to construct a 3D space-time map
showing that within 500 light-years of
our planet, all of the young stars and
star forming regions reside on the
surface of our local hot bubble. With
these 3D positions and the 3D motions of
the stellar clusters, they traced back
20 million years of star formation
history near our local hot bubble. The
implications were clear that all of the
well-known star forming regions near our
solar system had formed along the outer
edge of the local bubble as it swept up
gas during its expansion.
Stella nurseries are a field we are
learning more about all the time.
particularly as new images are taken by
our telescopes. Here's a spectacular
image of the Chameleon 1 dark cloud, one
of our nearest stellar nurseries, taken
by a dark energy camera on the Victor M.
Blanco 4 m telescope at Cherro Talo
Interamerican Observatory. By studying
the propagation of starlight from within
it, scientists can tease out details
about how stars form, which might help
us better understand the local hot
bubbles impact on our galaxy today. You
might not have seen this particular
image before as new space news is coming
out all the time, but I've talked about
it in my newsletter, which I've recently
launched to help you keep up with all
the breathtaking photos released by our
many telescopes on Earth and in orbit,
or new breakthroughs that reshape how we
understand the cosmos. You should sign
up to never miss the most exciting news,
even if the headlines do, by following
the link in the description below. There
are new editions that come out every
Thursday.
From the local hot bubbles birth 14
million years ago, Zucker and her
colleagues identified four epochs of
star formation on the bubble shell.
Starting about 16 million years ago, we
see the birth of the upper centurus
lupus or the UCL star cluster, followed
by the lower centurus crux or LCC star
cluster.
These formed about 49 light years apart
from one another. And about 14 million
years ago, these stellar populations
were the source of the stars that went
supernova to create our local bubble.
About 10 million years ago, we see the
first of the four star forming epochs
after the formation of the LHB. The
upper scorpius association and older of
stellar populations are born in the
first epoch. 6 million years ago the
second star forming epoch formed Corona
Arralis and the older stars of Taurus.
Then around 2 million years ago, the
stars in Lupus and Chameleon as well as
younger stellar populations of Taurus
and ofucas came to be in the third
epoch. And finally, our present time
falls within the fourth star forming
epoch. We can observe the dense star
forming molecular gas that surrounds the
LHB, which will eventually lead to more
star clusters being born along the
bubble's outer edge.
With all of this stellar creation, you
might be surprised to learn that we are
interlopers.
Our sun did not form inside the local
bubble. In fact, the sun was about 978
light years away when the first
supernova went off in UCL and LCC, only
joining up with the LHP about 5 million
years ago as its path through the galaxy
took it into the bubble. With the
trajectory shown in yellow dots, you can
see our sun's location just before it
entered the bubble. And now, just by
coincidence, our sun happens to be
located near the center of the LHB.
Drifting into the heart of what was once
a raging furnace, scientists became
interested in mapping out the ongoing
temperature within the local bubble. You
might wonder why we're so calm if
temperatures of plasma here can reach 1
million° C.
The key lies in that plasma's density.
Look, this 3D map from Zucker's 2022
publication shows our local hot bubble
in dark blue. The density inside our
bubble is extraordinarily low,
containing about 100 times less hydrogen
than the typical interstellar medium. So
while the temperature of this gas
soarses to around 1 million degrees
Kelvin, giving rise to the diffuse X-ray
emissions we have observed around the
whole sky, we don't have much to worry
about.
Tracking temperatures within the local
bubble has provided more evidence of its
existence. The extended renen survey
with an imaging telescope array, better
known as the E-Resistor X-ray telescope,
has been able to gather the most
detailed all sky survey of soft X-rays
to date. And that data has been used to
map the LHB and our solar neighborhood
in much more detail than before.
launched aboard the joint Russian and
German mission Spectrum Renen Gamma or
Spectre RG in 2019. Data from the E.
Rosita X-ray telescope has allowed a
team of scientists led by the Maxplank
Institute for Extraterrestrial Physics
to create a 3D map of the LHB and
identify a temperature gradient where
the galactic south was slightly hotter
than the galactic north.
This temperature dichotomy could be
explained by supernova explosions in the
past few million years. And by creating
this bubble map, the team also found
that the LHB is stretched out towards
the poles of the galactic hemisphere.
This is because the hot gas in the
bubble expands out in the direction with
the least resistance, which happens to
be away from the Milky Way's galactic
disc. Along with identifying temperature
variations and the shape of the bubble,
the team compiled this and other data to
create an even more detailed map of our
galactic neighborhood. In the new 3D
map, our local hot bubble looks like a
three-dimensional splatter surrounded by
and even overlapping other galactic
structures. These other structures
represent known supernova remnants like
the Gum Nebula shown here in red and
dense molecular clouds shown here in
orange.
With the new data and 3D maps, these
super bubbles seem likely to be common
in our galaxy, creating a Milky Way
that's sort of like Swiss cheese. The
cavities of our Swiss cheese galaxy are
blasted out by gigantic supernova
explosions with new stars forming along
the edges of the holes created by dying
stars. And like Swiss cheese, it appears
that some of these super bubbles may
have tunnels connecting them to other
bubbles or other structures, suggesting
our local hot bubble could be part of an
intricate network of similar features
throughout our galaxy. For example, we
have the Canis Majorus Tunnel, which
lies on the Milky Way's galactic disc
and is believed to connect our local hot
bubble to the Gum Nebula, or another
larger nearby superb bubble. But the 3D
map also revealed another previously
unknown interstellar tunnel stretching
towards the constellation Centurus,
possibly connecting our local bubble to
the neighboring Loop 1 superb bubble.
While these interstellar tunnels are
tantalizing, our current understanding
of them is limited. Nevertheless, these
tunnels of hot gas and bubbles of star
formation shaped by the death of
gigantic older stars has me in awe of
how powerful and interconnected the
evolution of our local galactic
neighborhood really is. He suggests that
stars are not just born and die in
isolation, but that their energetic
output continues to mold the environment
for millions of years after their
demise.
And as our observational tools become
more sophisticated, we are beginning to
uncover the extent of these hidden
structures.
So next time you look up at the night
sky, you might remind yourself that we
are surrounded by crazy patterns. just
like our local bubble in the Milky Way
that was carved out by ancient
cataclysms. And that some of those stars
that you see are actually plastered
along the walls of a supernova blasted
cavity which connects to other parts of
the galaxy through interstellar tunnels.
Wow.
Imagine
for a moment that you're looking out
your window when a singular bright light
suddenly flares into existence in the
sky above you. This dazzling star is as
luminous as the full moon at night,
perhaps brighter, and is even visible
during the day.
If you can see the light, you might
already be in trouble as that unexpected
star is now flooding the atmosphere of
the Earth with a catastrophic dose of
gamma radiation and X-rays, stripping
away our ozone layer and exposing us to
the full fury of the sun's deadly
radiation.
And on its way, jettisoned out at 10,000
to 40,000 km/s,
a cataclysmic wave of stellar matter and
debris hurdles towards our planet. The
dying roar of an exploding star venting
billions of tons of burning mass at us,
ready to sweep across our planet's
surface in a tidal wave of fire. This is
a supernova. or at least it's one
interpretation of what we might see if
one were to occur near us. But how
likely is it for this to actually
happen? What constitutes near us on a
cosmic scale? How close would a
supernova blast have to be before life
on Earth would be threatened? What might
we on Earth actually experience? And
what stars near us have the potential to
detonate in this way?
I'm Alex Mccoan and you're watching
Astramm. Join with me today as I discuss
an event that could be an Armageddon in
our lifetimes or could be nothing more
than a pretty twinkle in the sky.
Let's start with the good news.
Supernova in our galaxy are not that
common. While astronomers observe
hundreds of supernova every year outside
our galaxy, this is mostly a reflection
on how many galaxies there are in the
universe. Closer to home, though, within
our own Milky Way, we likely only see
about 2 to three every century.
This means that the odds of one going
off tomorrow are not that high. But
they're not impossible. And according to
archaeologists, the Earth has likely
been hit by a supernova before in the
course of its 4.5 billion years of
existence. For starters, we exist in an
area of space known as the local bubble,
a relatively sparssely populated region
of interstellar space about 1,000 lighty
years across that is thought to have
been carved out by a supernova
detonation 10 to 20 million years ago,
which our planet would have been around
for. I talk about that in another of my
videos which you can see here.
Scientists have found evidence of
another detonation that happened 2 1/2
million years ago due to a high
concentration of iron 60 and manganese
53 in a particular layer of the
geological record. This supernova
happened far enough away to be harmless
to us. But this might not always be the
case. There are some scientists who
believe that the extinction of woolly
mammoths was caused by a massive piece
of debris from a supernova crashing into
the planet about 13,000 years ago. The
impact site in question had magnetic
sphererals and radioactive potassium 40,
a substance found in supernova ejector.
A smoking gun in the era most mammoths
went extinct. Even before that, mammoth
tusks from 34,000 years ago were found
containing tiny impact craters from
grains of slightly radioactive iron that
had been traveling at 10,000 km/s.
If you can recall, that was one of the
potential speeds supernova explosions
travel at. That can't have been a nice
experience for the mammoths in question.
An astute observer from this might be
able to note an important fact, however.
Evidently, if life began on Earth about
3.7 billion years ago, and we faced
three supernova explosions that have
impacted us in the last 20 million
years, and life is still largely ticking
along, my condolences, woolly mammoths,
if you did die out from one of these,
then supernova as a whole can't be quite
as destructive as my opening
introduction made them out to be. And
that's largely true. Although it is, of
course, a question of proximity. If I'm
1,000 km away from a nuke going off, I
have little to fear. But it's a
different story if one detonates on my
coffee table. And when it comes to
supernova, it turns out that the
universe has relatively large coffee
tables.
To understand the scale of these
explosions, it's necessary to understand
the forces involved, which means we need
to understand a little better about how
supernova happen. It turns out that
there's two main paths stars can take to
get to that explosive grand finale.
Although in each case, it has to be the
right kind of star. For the first path,
resulting in a type 1A supernova, it
usually needs to be a white dwarf in a
binary system that's gradually or
speedily siphoning matter away from its
neighboring star until it reaches a
point of critical mass. This path is not
fully understood, but it's thought that
a white dwarf or a dense star comprising
of mostly carbon in a giant super
diamond core is normally finally
balanced between two powerful opposing
forces. Electron degeneracy pressure and
gravity.
This simply means that atoms usually
object to being squashed too much. Their
electrons like to remain at certain
distances from the nucleus of the atom
and will resist being pushed denser than
this point. But gravity is an incredibly
powerful force that seeks to draw matter
closer, particularly in a dense mass
like a white dwarf, where a section the
size of a sugar cube has the mass of
around a car. And in a binary system
where the white dwarf is absorbing more
and more matter from its neighboring
star, eventually gravity overwhelms
electron degeneracy pressure and the
whole house of cards collapses at once.
Carbon fusion begins. Within a few
seconds, most of the star underos
fusion, forming into heavier elements
and releasing a whole lot of energy as
the matter in the star settles into its
slightly more efficient new
configuration.
How much energy? Around 1 quarter
rotorillion jewels. That's one followed
by 45 zeros. If you claim you knew that
number before, you're almost certainly a
liar.
All of this energy is released in just a
few seconds. So naturally, the star
ejects its entire contents out in all
directions, sending it traveling at 6%
the speed of light and unleashing a
flood of mostly gamma radiation out
across the galaxy. The brightness of
this event is 5 billion times brighter
than our sun and burns for a few weeks
until the ejector has traveled far
enough that the overall energy level has
started to dissipate.
The second type of supernova, type two,
is similar, except instead of involving
a white dwarf, it involves a massive
star, at least five times more massive
than the sun at the end of its lifetime.
These stars are still burning brightly.
And rather than just electron degeneracy
pressure, it's also the heat of fusion
that keeps the star in balance. However,
just like a type 1A supernova,
eventually balance collapses.
This time is because the star runs out
of fuel. And without this additional
fusion energy pushing the stars mass
outwards, electron degeneracy pressure
on its own can't cope with the stars
weight to similar effect. The only
difference is that while some of a
massive star will remain, often
collapsing down into a neutron star or a
black hole, white dwarfs usually vanish
completely.
Either way, the scale of material and
energy released by a supernova is vast.
So vast that unsurprisingly, anything
immediately next to it is not going to
last long. This is an energy powerful
enough to rip apart a star. A planet is
going to have no chance if it's in the
immediate vicinity. Our own sun
thankfully will never go supernova as
it's not massive enough. But if it did,
there is a good chance the Earth would
be either partially or completely
vaporized. its rocky exterior reaching a
boiling point thanks to temperatures 15
times hotter than the surface of our sun
and being whisked away in the weeks of
the supernova's passing.
What is surprising, however, is how
quickly this first wave of devastation
would dissipate with distance. Indeed,
vaporization is realistically not the
largest threat supernova poses. In 2011,
experts from the University of Cambridge
calculated that even planets orbiting
their star at a distance of 15 billion
km, or about 100 times the distance
between the sun and the Earth, would
remain intact and would instead simply
be sent flying out into space now that
there was nothing much left to orbit. Of
course, such a planet's hypothetical
ecosystem would probably have different
problems to worry about. things would
get very cold very quickly. Of course,
even if the crust of a planet itself
remained intact, that doesn't mean that
life on said planet would be
sustainable. Ignoring the light of a
supernova outperforming the brightness
of an entire galaxy sometimes, leading
to blindness for anyone who saw it.
Simply stripping away our atmosphere
would carry problems. High levels of
radiation, even if it didn't affect us
directly, would alter the chemical
composition of our atmosphere, negating
our ozone layer, vastly increasing our
odds of dying of radiation poisoning and
killing off phytolanton in the ocean and
causing mass extinctions as the
consequences of that worked its way up
the food chain. Scientists put this kill
zone to be within 25 light years. Beyond
that, the fury of a supernova begins to
calm as distance causes it to wear
itself out. Although admittedly, the
asteroid that potentially killed the
mammoth came from a supernova that was
250 lighty years away, if it happened at
all, it was likely bad luck. Generally
speaking, we wouldn't notice any damage
from a supernova this far away. Its
radiation levels wouldn't be high enough
to cause mass extinctions. by 500 lighty
years, we'd hardly notice the event at
all other than perhaps seeing a brighter
star in the sky. Which leaves one
important question. Within 300 lighty
years, are there any supernova
candidates we need to worry about?
Thankfully, scientists are fairly
confident that the answer is no. Massive
stars are very noticeable, and the only
two that are at risk of going supernova
are Beetlejuice and Antaris.
Both of those are more than 400 lighty
years away. White dwarfs are a little
trickier thanks to their diminished
brightness. They've been conventionally
hard to spot, making it harder to
predict whether we might be at risk from
them. However, in 2013, ISA's Gaia Space
Observatory released a massive packet of
information in its efforts to map the
stars that allowed scientists to
identify 13,000 white dwarf stars within
326 lightyears of us. Thankfully, in
spite of this large number, scientists
remain confident that none of these are
scheduled to explode anytime soon.
Soon meaning within the next few
hundred,000 years.
Speaking of Beetlejuice, there are some
scientists who predict that this red
giant might detonate much sooner than
that, perhaps within the next few
decades.
Their research works under the
assumption that Beetlejuice has a much
larger radius than previously predicted.
But if it's true, it might mean that we
would get to see a local supernova
within our lifetimes.
Of course, according to some models, we
would have nothing to worry about. The
shock wave traveling out from
Beetlejuice would take some time to get
to us, and even once it arrived, it
would be traveling with less force than
the push of the solar wind. In other
words, it wouldn't be our magnetosphere
or atmosphere that kept us safe. The
protective sheath of the sun's
heliosphere would be enough to keep such
a supernova at bay.
So, there you have it. While supernova
are perhaps some of the largest
explosions in the universe, through some
fortunate stroke of luck, our patch of
galaxy has nothing really to fear from
them. The odds of us being hit by even
the neighboring stars like Beetlejuice
that are scheduled to go supernova are
incredibly small. True, Earth has plenty
of cataclysms of its own, such as
floods, earthquakes, and hurricanes that
can bring devastation to a community in
a heartbeat, and space is still a
dangerous place. But it's nice to know
that of all the things we have to worry
about, we can probably cross planetary
annihilation from supernova off our
list.
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.
[Music]
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 nanm,
allowing it to detect otherwise
invisible objects like stars obscured by
dust and cold 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 VV 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 Triford Nebula, which lies
about 9,000 lightyears 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 Trifid 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
seeded variable stars. While they appear
in the image to be just behind the edge
of the Trifford 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 Omicron
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 seaf 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
seafoods 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 seafs
culminated in another major discovery.
By mapping the 35 classical seafs 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 sea feeds 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 seafoods 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 R Lray, 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 CL00001.
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 CL00001 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 melanic 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 Gaia
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.
Some of you may remember my first video
I ever did on my channel, which was how
big is our solar system if the the sun
was the size of a football or a soccer
ball. Uh, today I'm going to do that
again, but this time I'm going to scale
it down a little bit where the sun is
only the size of 1 millm, like a grain
of sand. We're going to see how big the
solar system is in comparison to the sun
being that big. So, we'll start off
first of all with the sun. I'm going to
put it just by here.
Now, the closest planet to our sun is,
of course, Mercury. And if the sun was 1
mm in diameter, that would mean Mercury
is 4 cm away. So, I'm going to put it
just by there. There's Mercury. So, the
next closest planet to the sun is Venus,
and it is 8 cm away. So,
There we have Venus.
The next one is us on Earth and that is
10 cm away.
[Music]
>> Then we have Mars which is 16 cm away.
The next one we'll mention here is
Sarah's dwarf planet found in the
asteroid belt and that is 30 cm away.
Okay, the next one is Jupiter and that
is 56 cm away.
We're getting far away now. Saturn is 1
m
and 3 cm away.
Coming to the first of the ice giants
now and we find Uranus which is massive
2 m and 6 cm away.
[Music]
The last real planet in our solar system
is Neptune and that is 3 m and 24 cm
away. So,
[Music]
and then we have Pluto which is 4 m and
22 cm. And this is the last thing that
we'll look at in our solar system.
[Music]
At this point, you may be wondering,
"What about the closest star, Alpha
Century?" Well, you're going to have to
follow me a little bit. So, uh, come on.
Let's go.
[Music]
Oh,
[Music]
hey.
[Music]
Heat. Heat. N.
[Music]
Heat. Hey. Hey. Hey.
Heat. Heat.
[Music]
Heat.
[Music]
Heat.
Heat. Heat.
[Music]
Heat. Heat.
[Music]
Heat. Heat.
[Music]
Heat. Heat.
[Music]
Heat. Heat.
[Music]
I know this wasn't really a straight
line, but yes, Alpha Century, if the sun
was the size just 1 mm, Alpha Century is
30 km away, and that's our closest star.
Thanks for watching. This video was in
part made possible by all the astronauts
on Patreon. If you think these videos
add some educational value to the world
and want to give them more stability
than the algorithm, you can become a
paid member on Patreon to contribute
towards their creation. When you join,
you'll be able to watch the whole video
ad free, see your name in the credits,
and submit questions to our team. Just
sign up with the link in the
description. Meanwhile, click the link
to this playlist for more Astramm
content. I'll see you next time.