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MIKE ROWE:
Our universe is at war.
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The universe is a very violent
and deadly place.
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ROWE: Entire galaxies
fight to the death.
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OLUSEYI: Talk about clash of
the Titans.
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It doesn't get more titanic
than this.
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It's a slaughter.
It's a massacre.
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ROWE: Only
the strongest survive.
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If a galaxy wants to stay alive,
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it has to feed on
other galaxies.
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ROWE: Our own galaxy
also fights for survival.
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We are facing
the ultimate destruction
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of the Milky Way Galaxy.
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ROWE: These battles are
how galaxies live,
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grow, and die.
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These collisions got us to
where we are today,
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and they're going to determine
the future of the universe.
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♪♪
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♪♪
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In 2018,
astronomers used the Gaia
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space telescope to map
our Milky Way Galaxy.
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They tracked the movements of
a billion stars,
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and they found that some
behave very strangely.
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When astronomers were
mapping stars in our galaxy,
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they found a whole bunch that
we're on similar
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but very strange orbits.
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Most stars of the Milky Way
are orbiting in a sort of
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regular pattern, but these stars
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at the center, they're in
these highly elongated orbits.
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Coming in from very far,
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swinging around the center of
our galaxy, and then going back
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out again, a little bit
like a comet does.
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ROWE: This group of
stars plunges
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wildly through
the center of our galaxy.
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When you track their direction
and speed on a chart,
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you get a shape that looks
a bit like a sausage.
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This doesn't sound
very science-y,
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but this sausage is really
what the stars look like
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if you look at the shapes
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of their orbits
in a certain configuration.
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ROWE: What sent so many
stars on such a strange path?
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It must have been a huge event.
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We think these stars are
the result of a past
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cosmic collision.
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ROWE: They are casualties
from an enormous battle between
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the Milky Way
and a foreign galactic army.
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BULLOCK: They don't move
like stars in the Milky Way,
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because they're not
from the Milky Way.
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These stars are
actually alien stars.
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They're invaders from outer,
outer space.
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ROWE: The attackers left
their mark on the Milky Way.
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We find similar battle scars
on galaxies across
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the universe.
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Our models of galaxy
information are still
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pretty uncertain.
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We still don't really
understand how galaxies got to
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where they are, how we go from
the Big Bang to the Milky Way.
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ROWE: Wars between galaxies
have profound consequences, for
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the winners,
the losers, and for us.
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What we're learning is that
these galactic battles have had
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a huge impact on what
the universe looks like today.
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THALLER: Our understanding
of galaxies has changed
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entirely in the last
few decades.
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We understand now that every
big galaxy like the Milky Way
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started from many smaller
things colliding,
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changing each other
as they went.
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ROWE:
Nearly 10 billion years ago,
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the sausage stars were part of
a foreign galaxy.
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It was on a collision course
with our home, the Milky Way.
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We call this invading army
the Sausage Galaxy,
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or Gaia-Enceladus.
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PLAIT: The galaxy that
we fought probably had
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about 50 billion stars,
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so we're talking about
something that is a significant
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fraction of the size of
the Milky Way.
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ROWE: Gaia-Enceladus
was a tough opponent,
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but the Milky Way
was 20 times its mass,
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and that makes
a huge difference.
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When galaxies interact
with each other,
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size definitely matters.
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The bigger galaxies are gonna
dominate over the smaller ones,
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ripping them apart and
essentially consuming them.
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Galaxy interactions
are all about bullies.
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The bigger you are,
the badder you are.
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SUTTER:
When two galaxies collide,
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it's like two massive armies
marching towards each other.
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These galaxies aren't fighting
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with knives or spears
or guns or even nuclear bombs.
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They're fighting with something
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much more powerful --
Gravity itself.
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ROWE: Each galaxy contains
billions of stars and planets
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and a supermassive black hole,
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millions of times
the mass of the sun.
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That's a lot of
gravitational firepower.
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SUTTER: As these galaxies
approach each other,
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you can get tidal effects --
The same way that the moon can
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raise tides on one side of
the Earth and the opposite side,
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one galaxy can stretch another
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galaxy along
a certain direction.
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ROWE: As Gaia-Enceladus
advanced towards us,
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our galaxy's superior
gravity grabbed
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hold of the smaller galaxy.
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As it approached, the gravity
from the Milky Way
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would have stretched it out.
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ROWE: Gaia-Enceladus was
distorted but not defeated.
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The battle was just beginning.
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It would have passed
through our galaxy,
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maybe orbiting a couple of
times before being torn
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apart by our gravity.
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ROWE: The Milky Way's
gravitational power
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ripped Gaia-Enceladus apart
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and captured billions of
its stars.
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Eventually, most of those
stars would have
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then settled down into
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the disk of the Milky Way
and become a part of it.
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Little galaxy try
to take on the Milky Way --
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You're gonna get
what's coming to you.
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ROWE:
Despite winning the battle,
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the Milky Way suffered
serious damage.
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The collision
with the Sausage Galaxy
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left a scar on the Milky Way.
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And when we look near
the center of our galaxy,
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we see a bulge that's left
over from that collision.
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ROWE: The Milky Way isn't
the only galaxy scarred by war.
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Across the universe,
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rival armies made up of
billions of stars slug it out,
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leaving behind distorted
and damaged casualties of war.
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HOPKINS:
There's a million different
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sub-categories of them.
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There's tadpole galaxies
that have long tails,
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longer than our own galaxy.
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There are things like
Arp-Madore 2026, where you see
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this eerie, glowing face,
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two big eyes looking right at
you from across the universe.
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There are galaxies that looked
like they might have collided
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with one another and blown
holes through each other.
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ROWE: These battle scars
give us important clues
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about one of the biggest
mysteries in astronomy --
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How galaxies develop and grow.
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But there's a problem.
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We can't watch
these battles in real time.
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The scale of galaxies is huge.
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They're hundreds of thousands
of light years across.
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It's going to take them millions
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or billions of years
to come together.
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So it's like looking at
one frame
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from a really energetic
fight scene in a movie.
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ROWE: By piecing these
snapshots together,
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astronomers can build up
a detailed picture of past
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conflicts and discover how
these battles transformed
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galaxies over billions of years.
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We have pictures of
isolated galaxies,
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we have pictures of
interacting galaxies,
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and we have pictures of
aftermath galaxies.
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ROWE: And that's helped us
discover something alarming.
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The Milky Way faces yet
another attack from
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an enemy armed with
an enormous secret weapon.
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Will our solar system
survive the onslaught?
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ROWE: Across the universe,
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galaxies are at war,
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Their main weapon --
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Gravity.
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It tears the combatants into
weird and wonderful shapes.
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Our galaxy didn't
escape the mayhem.
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It's peppered with battle scars.
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The overall shape
of the Milky Way
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is a flat disk of stars and gas.
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Except recently, we have found
out that at the edges,
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it's actually warped a little
bit like the brim of a fedora.
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The stars actually dip down
below the plane on
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one side and dip above it
on the other.
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ROWE: We think the attacker
was one of our satellites,
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a galaxy that orbits
the Milky Way like the moon
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orbits the Earth.
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It's called the Sagittarius
Dwarf Galaxy.
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From looking at how
the stars move in the Milky Way,
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we suspect that
the Sagittarius Dwarf Galaxy has
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actually crashed through
the Milky Way a few times on
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its course of its orbit
around the galaxy.
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BULLOCK: It came in
about six billion years ago,
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hit the disk hard about two
billion years ago, and crashed
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again about a billion years ago.
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PLAIT: And our gravity has
pulled it out into a gigantic,
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looping stream of stars that
is moving in and out
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of our Milky Way.
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ROWE: The war is not over.
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The insurgent galaxy
will return.
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When galaxies interact,
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often they're caught in this
huge cosmic dance
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where they revolve around
each other a few times,
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or they even crash through
each other and then come
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back around.
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The Sagittarius Dwarf Galaxy
looks like
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it's crashing in with ever
increasing frequency.
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ROWE: A new skirmish could
take place in the next
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100 million years.
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So should we be worried
about these attacks?
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SUTTER: Because the Sagittarius
Dwarf Galaxy is so small
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compared to the Milky Way,
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it will do some damage at
the beginning,
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but because we're so massive,
we can absorb the impact.
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I mean, this galaxy,
it's looking for a fight,
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but it's also 10,000 times
smaller than us.
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So this is gonna be
no sweat at all.
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ROWE: So far, the Milky Way
has been victorious.
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But the danger isn't over.
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We are surrounded by enemies.
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SUTTER: Our local
neighborhood of galaxies
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has three major galaxies,
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but up to 50 smaller ones.
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All these galaxies are
potential troublemakers.
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Each one of these could be
armies that rise up against us.
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The two most famous
galaxies that orbit
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the Milky Way are the Large
and Small Magellanic Clouds.
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These are two independent
dwarf galaxies that you can
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see in the night sky from
the Southern Hemisphere.
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ROWE: We thought the Large
Magellanic Cloud orbited
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our galaxy at a safe distance
of 160,000 light years.
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We thought it would
stay that way,
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and we thought it was harmless.
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Now, a new discovery shows
we were wrong on all counts.
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The new factor that changed our
view of the Magellanic Cloud
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is we found out
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it has a lot more
dark matter than we thought.
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ROWE: Dark matter,
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the most mysterious stuff
in the universe.
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A dark matter is literally
what it sounds like.
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It's matter that we cannot see.
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00:12:30,750 --> 00:12:32,884
But it has gravity and can
affect objects
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that we can see.
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ROWE: Adding in this extra
dark matter makes the Large
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Magellanic Cloud at least
twice a massive as predicted.
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So its gravity is double
what we thought.
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It's secretly been gathering
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00:12:53,172 --> 00:12:57,442
allies, has been gathering
dark matter on its side,
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and now it's a much bigger
threat than we thought before.
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00:13:02,414 --> 00:13:04,249
So it's not just
going to orbit us.
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It's gonna collide
with the Milky Way.
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ROWE: Moving at nearly
a million miles an hour,
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the Large Magellanic Cloud
will not swing past us.
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It will attack.
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00:13:17,630 --> 00:13:19,998
The large Magellanic Cloud is
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1/10 the mass of the Milky Way.
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00:13:23,469 --> 00:13:26,304
That's enough to make
a pretty big punch.
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ROWE:
In about 2.5 billion years,
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it will smash into our galaxy.
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SUTTER: It's gonna plow through
the disk of the Milky Way,
247
00:13:39,318 --> 00:13:40,819
it's gonna blow a cavity.
248
00:13:40,920 --> 00:13:43,621
It might even damage
our spiral arms.
249
00:13:45,991 --> 00:13:49,327
ROWE: Earth sits in one of
those spiral arms.
250
00:13:51,597 --> 00:13:54,365
Could our planet become
collateral damage?
251
00:13:55,835 --> 00:13:58,436
If the Large Magellanic Cloud
passes through the plane
252
00:13:58,537 --> 00:14:01,239
of our galaxy near our location,
253
00:14:01,340 --> 00:14:03,308
that can have dire consequences.
254
00:14:05,010 --> 00:14:07,078
ROWE:
The gravitational clash between
255
00:14:07,179 --> 00:14:09,147
the invader on the Milky Way
256
00:14:09,248 --> 00:14:12,350
could hurl stars and
planets out of our galaxy.
257
00:14:14,220 --> 00:14:16,087
Earth could be one of them.
258
00:14:17,723 --> 00:14:20,525
HOPKINS: Our planet's very
close to its own star,
259
00:14:20,626 --> 00:14:23,828
so the odds are that you'll
just get ripped out
260
00:14:23,929 --> 00:14:25,096
along with your star,
261
00:14:25,197 --> 00:14:28,132
so we'd be moving along with
the sun even as the sun gets
262
00:14:28,234 --> 00:14:30,869
jettisoned from our galaxy.
263
00:14:30,970 --> 00:14:33,705
PLAIT: And it'll move off out
into intergalactic space.
264
00:14:33,806 --> 00:14:35,506
And that's not terrible.
265
00:14:35,608 --> 00:14:37,375
I mean, it's not gonna
get destroyed,
266
00:14:37,476 --> 00:14:38,710
but it's a little lonely.
267
00:14:42,014 --> 00:14:44,482
ROWE: Our view of the night sky
268
00:14:44,583 --> 00:14:45,984
would radically change.
269
00:14:47,586 --> 00:14:50,455
OLUSEYI: We'd be able to see
much more of the Milky Way,
270
00:14:50,556 --> 00:14:54,225
especially if we got kicked up
above the plane of the galaxy.
271
00:14:54,326 --> 00:14:56,794
We'd be able to see
the whole shebang.
272
00:14:56,896 --> 00:15:00,531
Just look at any image of
a spiral galaxy.
273
00:15:00,633 --> 00:15:03,768
They're gorgeous.
Now imagine seeing your night
274
00:15:03,869 --> 00:15:07,338
sky filled with
a face-on spiral galaxy.
275
00:15:07,439 --> 00:15:09,908
[scoffs] That would be like
waking up to my face
276
00:15:10,009 --> 00:15:12,810
every morning -- spectacular.
277
00:15:12,912 --> 00:15:15,546
[laughs]
278
00:15:17,449 --> 00:15:19,951
ROWE: If we were unlucky,
279
00:15:20,052 --> 00:15:21,619
our home planet could have
280
00:15:21,720 --> 00:15:25,023
a close encounter with
an invading star.
281
00:15:25,124 --> 00:15:28,927
PLAIT: The odds are very low
that another star
282
00:15:29,028 --> 00:15:30,728
will pass close by the sun,
283
00:15:30,829 --> 00:15:32,764
but those odds aren't zero.
284
00:15:32,865 --> 00:15:34,565
It could happen
that another star
285
00:15:34,667 --> 00:15:36,734
passes close enough
to affect the planets.
286
00:15:36,835 --> 00:15:38,503
And if that were to happen,
287
00:15:38,604 --> 00:15:43,541
it could upset the delicate
balance in the solar system.
288
00:15:44,576 --> 00:15:47,779
OLUSEYI: We don't know where
the Earth could end up.
289
00:15:47,880 --> 00:15:49,847
It might find its way
into the sun.
290
00:15:49,949 --> 00:15:50,982
You just don't know.
291
00:15:51,083 --> 00:15:52,850
Or there might just be a rain
292
00:15:52,952 --> 00:15:55,386
of comets into
our inner solar system.
293
00:15:55,487 --> 00:15:57,922
MINGARELLI: Our own planet
might be flung out,
294
00:15:58,023 --> 00:16:01,225
in which case, this would be
a death knell for all life
295
00:16:01,327 --> 00:16:02,560
on Earth.
296
00:16:02,661 --> 00:16:05,263
I'm not someone who is like
a doom and gloom person,
297
00:16:05,364 --> 00:16:07,165
but, like, that would be insane.
298
00:16:08,500 --> 00:16:10,068
OLUSEYI: You don't know
what's gonna happen,
299
00:16:10,169 --> 00:16:13,338
but most of the options are bad.
300
00:16:13,439 --> 00:16:16,641
ROWE:
All these nightmare scenarios
301
00:16:16,742 --> 00:16:18,476
will extinguish life.
302
00:16:22,114 --> 00:16:24,983
Earth might survive,
but our cosmic
303
00:16:25,084 --> 00:16:27,618
zip code will take
a severe beating.
304
00:16:29,221 --> 00:16:31,422
SUTTER: The Milky Way Galaxy
is bigger than
305
00:16:31,523 --> 00:16:32,623
the Large Magellanic Cloud,
306
00:16:32,691 --> 00:16:35,426
so we are gonna win,
[exhales heavily]
307
00:16:35,527 --> 00:16:37,328
but it's gonna hurt us
for a long time.
308
00:16:39,031 --> 00:16:40,598
ROWE: The Large Magellanic Cloud
309
00:16:40,699 --> 00:16:42,667
will leave our galaxy battered,
310
00:16:42,768 --> 00:16:45,737
bruised,
but ultimately undefeated.
311
00:16:45,838 --> 00:16:49,741
But there's a far bigger
threat looming
312
00:16:49,842 --> 00:16:51,576
over the Milky Way.
313
00:16:51,677 --> 00:16:54,612
It's gonna face an opponent
that it can't defeat.
314
00:16:55,981 --> 00:16:58,182
ROWE:
Will this mega collision be
315
00:16:58,283 --> 00:17:00,585
the Milky Way's last stand?
316
00:17:11,630 --> 00:17:13,131
ROWE: For billions of years,
317
00:17:13,232 --> 00:17:16,234
the Milky Way conquered
galaxy after galaxy,
318
00:17:16,335 --> 00:17:19,837
tearing its smaller rivals
to pieces.
319
00:17:21,106 --> 00:17:24,075
But our galaxy is about
to meet its match.
320
00:17:27,112 --> 00:17:31,082
In the not-too-distant future,
galactically speaking,
321
00:17:31,183 --> 00:17:34,819
a much, much larger battle
is due for the Milky Way.
322
00:17:36,522 --> 00:17:38,923
ROWE: A battle
with a local superpower,
323
00:17:40,225 --> 00:17:41,526
the Andromeda Galaxy.
324
00:17:43,095 --> 00:17:46,731
We thought this huge galaxy
might wound us in the future.
325
00:17:48,167 --> 00:17:51,702
Now, recent evidence reveals
it's going to make
326
00:17:51,804 --> 00:17:54,472
a full-scale assault.
327
00:17:54,573 --> 00:17:58,109
We've known for a long time
that Andromeda is heading
328
00:17:58,210 --> 00:18:00,378
more or less toward us,
329
00:18:00,479 --> 00:18:02,847
but we didn't know exactly
in what direction.
330
00:18:02,948 --> 00:18:04,549
But in recent years, we've been
331
00:18:04,650 --> 00:18:06,651
able to pinpoint
this a lot better.
332
00:18:06,752 --> 00:18:10,354
And, uh, yeah, it's --
It's heading right for us.
333
00:18:13,092 --> 00:18:16,160
ROWE: Data from the Hubble
Space Telescope shows
334
00:18:16,261 --> 00:18:20,164
two galaxies will collide in
about four billion years,
335
00:18:23,001 --> 00:18:26,871
and it will be
a monumental battle.
336
00:18:26,972 --> 00:18:30,875
This collision that is coming,
and it is coming, is not gonna
337
00:18:30,976 --> 00:18:33,411
be anything like the Milky Way
has experienced before
338
00:18:33,512 --> 00:18:35,613
in its 10-
or 12-billion-year history.
339
00:18:35,714 --> 00:18:38,316
This is a galaxy of
comparable size.
340
00:18:38,417 --> 00:18:42,720
This is two heavyweight prize
fighters coming at it.
341
00:18:42,821 --> 00:18:46,924
ROWE: Warriors with the same
gravitational firepower.
342
00:18:47,025 --> 00:18:50,795
Simulations suggest
a clash of the Titans.
343
00:18:50,896 --> 00:18:53,331
BASRI: Each of them with half
a trillion stars in them.
344
00:18:53,432 --> 00:18:55,900
That sounds like a pretty
spectacular collision.
345
00:18:57,970 --> 00:19:00,905
ROWE: Fights between
equally matched galaxies
346
00:19:01,006 --> 00:19:03,508
are rare and messy.
347
00:19:03,609 --> 00:19:05,576
When the battle kicks off,
348
00:19:05,677 --> 00:19:08,579
there will be no good news
for either side.
349
00:19:10,749 --> 00:19:13,384
PLAIT: When the Andromeda Galaxy
and the Milky Way Galaxy
350
00:19:13,485 --> 00:19:14,852
start to get close,
351
00:19:14,953 --> 00:19:16,521
they're gonna start
affecting each
352
00:19:16,622 --> 00:19:17,688
other profoundly.
353
00:19:17,789 --> 00:19:20,057
Tendrils of stars are gonna be
thrown out.
354
00:19:20,159 --> 00:19:23,961
Gas is gonna be thrown out.
355
00:19:24,062 --> 00:19:26,564
ROWE:
It won't be a single impact.
356
00:19:26,665 --> 00:19:29,600
Gravity will send
the two opponents
357
00:19:29,701 --> 00:19:32,436
into a spiraling dance of death.
358
00:19:34,606 --> 00:19:36,874
PLAIT: The first pass is
actually not a direct hit.
359
00:19:36,975 --> 00:19:39,677
They're gonna swing past
each other, in fact.
360
00:19:39,778 --> 00:19:42,180
And at this point,
their gravitational
361
00:19:42,281 --> 00:19:43,781
interaction is gonna
slow them down,
362
00:19:43,882 --> 00:19:46,017
and they're gonna come
back toward each other.
363
00:19:46,118 --> 00:19:49,654
ROWE: The galaxies will
collide and fly apart again,
364
00:19:49,755 --> 00:19:54,292
inflicting more and more
damage with each clash.
365
00:19:54,393 --> 00:19:56,928
If you were to go
outside and look up,
366
00:19:57,029 --> 00:20:00,031
you could see the disk of our
galaxy getting ripped apart
367
00:20:00,132 --> 00:20:02,300
by tidal interactions
with Andromeda.
368
00:20:05,971 --> 00:20:09,307
ROWE: The two beautiful
spiral galaxies
369
00:20:09,408 --> 00:20:11,709
will tear each other apart,
370
00:20:11,810 --> 00:20:16,347
leaving one vast
elliptical galaxy.
371
00:20:18,283 --> 00:20:21,352
PLAIT: The fate of
the Andromeda, Milky Way
372
00:20:21,453 --> 00:20:24,689
battle is that they will merge.
373
00:20:24,790 --> 00:20:28,392
This is going to be
one gigantic galaxy.
374
00:20:31,463 --> 00:20:32,730
OLUSEYI:
And that presents a problem.
375
00:20:32,831 --> 00:20:34,498
What are we gonna
call this new galaxy?
376
00:20:34,600 --> 00:20:37,568
Of course, my nerd colleagues
have come up with
377
00:20:37,669 --> 00:20:40,504
names like Milkomeda,
Andromeway.
378
00:20:40,606 --> 00:20:42,740
Whatever, those are corny.
379
00:20:42,841 --> 00:20:44,875
We should just call it Hakeem.
380
00:20:50,949 --> 00:20:53,484
ROWE: With a trillion stars,
it will be
381
00:20:53,585 --> 00:20:56,420
one of the biggest galaxies
in the universe.
382
00:20:58,957 --> 00:21:00,124
OLUSEYI: In the Hakeem Galaxy,
383
00:21:00,225 --> 00:21:02,260
things gonna be completely new.
384
00:21:02,361 --> 00:21:05,663
First off, it's gonna be
a really good-looking galaxy.
385
00:21:05,764 --> 00:21:07,498
Let's get that straight
from the get-go.
386
00:21:07,599 --> 00:21:12,637
Second, it's gonna be powerful,
and I'm talking powerful.
387
00:21:12,738 --> 00:21:14,372
This may be the most remarkable
388
00:21:14,473 --> 00:21:16,574
galaxy in the history
of the universe.
389
00:21:19,111 --> 00:21:23,080
ROWE: Milkomeda, or Hakeem,
if you prefer,
390
00:21:23,181 --> 00:21:26,550
will become the undisputed boss
of our cosmic neighborhood.
391
00:21:26,618 --> 00:21:30,121
It's calm appearance concealing
392
00:21:30,222 --> 00:21:31,789
a history of violence.
393
00:21:34,826 --> 00:21:37,962
It's the result of a complete
war zone of mergers over
394
00:21:38,063 --> 00:21:39,230
the course of billions of years,
395
00:21:39,331 --> 00:21:42,333
many galaxies crashing
together, fully reconfiguring
396
00:21:42,434 --> 00:21:44,502
each time and slowly, you grow
397
00:21:44,603 --> 00:21:48,172
this smooth, placid,
big blob of stars.
398
00:21:50,242 --> 00:21:53,077
ROWE: After billions
of years of warfare,
399
00:21:53,178 --> 00:21:56,147
our galaxy will finally
be peaceful.
400
00:21:58,750 --> 00:22:02,586
But before it's honorable
discharge, Milkomeda
401
00:22:02,688 --> 00:22:04,755
may produce one final,
402
00:22:04,856 --> 00:22:07,625
devastating act of war.
403
00:22:07,726 --> 00:22:11,896
Imagine World War II,
and then all of a sudden,
404
00:22:11,997 --> 00:22:14,865
one of the sides comes
up with the Death Star.
405
00:22:14,966 --> 00:22:16,500
That's what
we're talking about here.
406
00:22:19,071 --> 00:22:21,405
ROWE:
A weapon of cosmic destruction.
407
00:22:21,506 --> 00:22:28,179
♪♪
408
00:22:37,789 --> 00:22:40,024
ROWE: When giant galaxies clash,
409
00:22:40,125 --> 00:22:43,094
the battles are spectacular
and destructive.
410
00:22:46,264 --> 00:22:50,401
The victors steal huge numbers
of stars and vast amounts
411
00:22:50,502 --> 00:22:55,272
of gas as fuel
for the ultimate super weapon.
412
00:22:57,342 --> 00:23:00,211
The special weapon
that these monster galaxies
413
00:23:00,312 --> 00:23:03,447
have is a giant Death Ray,
414
00:23:03,548 --> 00:23:08,419
a jet of material racing across
thousands of light-years.
415
00:23:10,822 --> 00:23:13,524
ROWE: These huge outbursts
of energy blast out
416
00:23:13,625 --> 00:23:16,694
of the center of
the colliding galaxies.
417
00:23:16,795 --> 00:23:20,030
They produce more energy
in one second than
418
00:23:20,132 --> 00:23:25,169
the sun will in its entire
10-billion-year lifetime.
419
00:23:25,270 --> 00:23:27,204
We call them jets.
420
00:23:28,974 --> 00:23:33,144
These incredibly powerful jets
aren't just brief features.
421
00:23:33,245 --> 00:23:36,380
They can be sustained
for millions of years,
422
00:23:36,481 --> 00:23:38,549
and they can maintain
their structure
423
00:23:38,650 --> 00:23:41,485
for thousands of light-years.
424
00:23:41,586 --> 00:23:43,454
It's like turning on
a garden hose
425
00:23:43,555 --> 00:23:45,856
in Chicago and using it to water
426
00:23:45,957 --> 00:23:47,591
a garden in London.
427
00:23:49,561 --> 00:23:52,563
ROWE: Exactly what triggered
these jets was a mystery.
428
00:23:52,664 --> 00:23:57,101
Then, in June 2018,
astronomers in Hawaii captured
429
00:23:57,202 --> 00:24:00,337
something stunning --
A jet forming
430
00:24:00,439 --> 00:24:02,840
during a galactic collision.
431
00:24:05,410 --> 00:24:07,578
The team found something
really incredible.
432
00:24:07,679 --> 00:24:11,015
They found two galaxies that
were in a cosmic collision
433
00:24:11,116 --> 00:24:14,318
and actually found an active
jet in one of these galaxies.
434
00:24:14,419 --> 00:24:16,754
It was the first time anything
like this has been discovered.
435
00:24:20,325 --> 00:24:23,961
ROWE: When galaxies collide,
the clash drives huge clouds
436
00:24:24,062 --> 00:24:27,465
of gas and dust towards
their centers.
437
00:24:27,566 --> 00:24:31,168
The supermassive black holes
start to feed.
438
00:24:33,371 --> 00:24:35,573
The gas that was in
those galaxies starts to
439
00:24:35,674 --> 00:24:39,376
funnel toward the black hole
and then fall upon it.
440
00:24:39,478 --> 00:24:42,012
ROWE: Not all this gas
ends up inside
441
00:24:42,113 --> 00:24:44,148
the supermassive black hole.
442
00:24:44,249 --> 00:24:46,650
Powerful magnetic fields carry
some of
443
00:24:46,751 --> 00:24:49,487
this matter to the poles
444
00:24:49,588 --> 00:24:52,723
and blast it out
in tight, narrow jets.
445
00:24:52,824 --> 00:24:55,759
A super weapon is born.
446
00:24:55,861 --> 00:24:57,761
This discovery helps
us understand
447
00:24:57,863 --> 00:25:01,832
how giant elliptical
galaxies form.
448
00:25:01,933 --> 00:25:05,503
Knowing that mergers of spiral
galaxies can cause
449
00:25:05,637 --> 00:25:07,204
these jets helps us put together
450
00:25:07,305 --> 00:25:09,807
a complete picture of
how these huge elliptical
451
00:25:09,908 --> 00:25:11,408
galaxies might be formed.
452
00:25:14,412 --> 00:25:18,215
ROWE: The discovery doesn't
answer all our questions.
453
00:25:18,316 --> 00:25:19,617
There's another mystery.
454
00:25:19,718 --> 00:25:21,952
How did the super giant
galaxies that
455
00:25:22,053 --> 00:25:25,055
dwarf the Milky Way get so big?
456
00:25:25,156 --> 00:25:29,360
Our Milky Way Galaxy is big-ish.
457
00:25:29,461 --> 00:25:31,529
It's -- it's slightly
bigger than average,
458
00:25:31,630 --> 00:25:33,864
but IC 1101, for example,
459
00:25:33,965 --> 00:25:37,635
is more than 50 times larger
than our home galaxy and has
460
00:25:37,736 --> 00:25:42,006
more than a trillion, with a T,
a trillion stars in it.
461
00:25:42,107 --> 00:25:47,177
The biggest galaxies make
the Milky Way look like an ant.
462
00:25:47,279 --> 00:25:50,881
These galactic giants
pose a problem.
463
00:25:50,982 --> 00:25:53,484
There hasn't been enough time
since the birth of
464
00:25:53,585 --> 00:25:57,721
the universe
for them to become so large,
465
00:25:57,822 --> 00:26:00,090
even by conquering
smaller galaxies.
466
00:26:00,191 --> 00:26:03,227
When we look into
the distant universe,
467
00:26:03,328 --> 00:26:06,530
we see something very strange
that we don't quite understand.
468
00:26:06,631 --> 00:26:09,600
We see enormous galaxies
that existed just
469
00:26:09,701 --> 00:26:11,502
a billion years
after the Big Bang.
470
00:26:11,603 --> 00:26:14,638
And even though these cosmic
collisions help explain how
471
00:26:14,739 --> 00:26:16,006
galaxies get bigger,
472
00:26:16,107 --> 00:26:18,943
they don't quite explain
everything about how galaxies
473
00:26:19,044 --> 00:26:20,077
grow over time.
474
00:26:20,178 --> 00:26:22,346
So we still have a big mystery
on our hands here.
475
00:26:26,217 --> 00:26:29,787
ROWE: So in 2019,
an international team
476
00:26:29,888 --> 00:26:32,356
investigated a very large galaxy
477
00:26:32,457 --> 00:26:35,392
over 300 million
light-years away.
478
00:26:35,493 --> 00:26:39,597
We call it NGC 6240.
479
00:26:39,698 --> 00:26:43,100
MINGARELLI: NGC 6240 was being
studied because
480
00:26:43,201 --> 00:26:45,769
it had two supermassive
black holes in it.
481
00:26:45,870 --> 00:26:48,071
Now the galaxy itself
looked like it
482
00:26:48,139 --> 00:26:50,140
had been disturbed,
like something had happened.
483
00:26:50,241 --> 00:26:53,711
They thought that potentially
it had had a recent merger.
484
00:26:59,284 --> 00:27:01,251
ROWE:
They were expecting to see two
485
00:27:01,353 --> 00:27:05,255
supermassive black holes
in the galaxy's heart.
486
00:27:05,357 --> 00:27:08,258
As the researchers peered
through the layers of gas
487
00:27:08,360 --> 00:27:12,429
and dust, they discovered
something surprising.
488
00:27:12,530 --> 00:27:14,698
What we found was staggering.
489
00:27:14,799 --> 00:27:17,368
We found not two but three
490
00:27:17,469 --> 00:27:20,237
supermassive black holes
lurking in the center.
491
00:27:26,611 --> 00:27:27,811
ROWE:
It's the first time we found
492
00:27:27,912 --> 00:27:32,416
a galaxy with three
supermassive black holes,
493
00:27:32,517 --> 00:27:35,986
evidence of
a three-galaxy pile up.
494
00:27:36,087 --> 00:27:40,124
This galaxy is an active
battlefield of
495
00:27:40,225 --> 00:27:46,096
not two but three armies
colliding at once,
496
00:27:46,197 --> 00:27:47,931
and because there are three
armies involved,
497
00:27:48,033 --> 00:27:50,167
there are three galaxies
involved with
498
00:27:50,268 --> 00:27:53,504
three times as much mass,
three times as many stars,
499
00:27:53,605 --> 00:27:56,206
three times as much material,
and three times as
500
00:27:56,307 --> 00:27:58,475
much violence.
501
00:27:58,576 --> 00:28:01,445
ROWE: This three-way battle
may explain how
502
00:28:01,546 --> 00:28:06,250
the largest galaxies
got so big so fast.
503
00:28:06,351 --> 00:28:08,118
MINGARELLI:
It could be that galaxy mergers
504
00:28:08,219 --> 00:28:11,121
are more frequent than
what we thought previously,
505
00:28:11,222 --> 00:28:14,725
and therefore,
galaxies become more massive
506
00:28:14,826 --> 00:28:16,860
faster than previously expected.
507
00:28:18,897 --> 00:28:21,031
ROWE: In the past,
galaxies may have
508
00:28:21,132 --> 00:28:24,401
battled and collided
more often than today.
509
00:28:24,502 --> 00:28:28,238
Back then, galaxies were more
densely packed together.
510
00:28:29,808 --> 00:28:33,310
Our universe is expanding
as it ages, which means in
511
00:28:33,411 --> 00:28:35,412
the past, all the galaxies in
512
00:28:35,513 --> 00:28:37,915
the universe were
closer together,
513
00:28:38,016 --> 00:28:40,017
and that means they had
greater chance for their
514
00:28:40,118 --> 00:28:41,618
gravitational interactions to
515
00:28:41,720 --> 00:28:43,921
pull them together
and smash them together.
516
00:28:46,591 --> 00:28:49,593
ROWE:
The early universe was at war.
517
00:28:49,694 --> 00:28:52,629
Conflicts between galaxies
were common.
518
00:28:52,731 --> 00:28:56,200
They collided frequently
and grew quickly.
519
00:28:57,769 --> 00:29:01,805
But not every galaxy profited
from the carnage.
520
00:29:01,906 --> 00:29:04,675
Some brave galaxies
took on the big guns
521
00:29:04,776 --> 00:29:06,744
and nearly died as a result.
522
00:29:21,526 --> 00:29:24,161
ROWE: When galaxies fight,
the big get bigger.
523
00:29:24,262 --> 00:29:28,398
More mass means more gravity,
the vital ingredient
524
00:29:28,500 --> 00:29:29,633
for victory.
525
00:29:31,803 --> 00:29:36,006
But galactic conflict doesn't
always result in growth.
526
00:29:36,107 --> 00:29:39,777
A strange new astronomical
object had
527
00:29:39,878 --> 00:29:41,245
scientists confused.
528
00:29:44,415 --> 00:29:46,717
MINGARELLI: They just looked
like stars from the ground.
529
00:29:46,818 --> 00:29:50,154
However, with the advent of
Hubble and beautiful
530
00:29:50,255 --> 00:29:51,955
space-based telescopes,
531
00:29:52,056 --> 00:29:56,059
it was possible to look at
these stars again and actually
532
00:29:56,161 --> 00:29:58,028
discover that
they were galaxies.
533
00:30:03,268 --> 00:30:04,635
HOPKINS: They're kind of crazy.
534
00:30:04,736 --> 00:30:09,807
They're a huge number of stars,
but crammed into an incredibly
535
00:30:09,908 --> 00:30:12,009
tiny space
on an astrophysical scale,
536
00:30:12,110 --> 00:30:16,446
something 500 times smaller
than our Milky Way Galaxy.
537
00:30:16,548 --> 00:30:20,384
ROWE: We call them
ultra-compact dwarf galaxies,
538
00:30:20,485 --> 00:30:21,819
or UCDs.
539
00:30:23,254 --> 00:30:25,756
HOPKINS: You might imagine
the difference between
540
00:30:25,857 --> 00:30:29,960
the Milky Way Galaxy
and a UCD as
541
00:30:30,061 --> 00:30:33,263
the difference between
a cloud and a rock,
542
00:30:33,364 --> 00:30:36,700
where the rock is just
the same kind of material,
543
00:30:36,801 --> 00:30:39,236
but compressed to just
incredibly high densities
544
00:30:39,337 --> 00:30:41,572
compared to some fluffy
gaseous thing.
545
00:30:44,576 --> 00:30:46,844
ROWE: What are these
strange galaxies?
546
00:30:46,945 --> 00:30:49,546
They seem to break
all the rules.
547
00:30:49,647 --> 00:30:52,983
To find out,
astronomers zoomed in to
548
00:30:53,084 --> 00:30:54,685
a particularly dense,
549
00:30:54,786 --> 00:30:57,321
ultra-compact dwarf galaxy
550
00:30:57,422 --> 00:31:00,724
called M60-UCD1.
551
00:31:01,993 --> 00:31:05,963
M60-UCD1 is
300 light-years across.
552
00:31:06,064 --> 00:31:07,998
It's tiny.
It's a pinpoint compared to
553
00:31:08,099 --> 00:31:09,433
our enormous galaxy.
554
00:31:09,534 --> 00:31:13,003
Our galaxy has 200 or more
billion stars in it.
555
00:31:13,104 --> 00:31:16,373
And M60-UCD1
only has 140 million.
556
00:31:16,474 --> 00:31:20,377
But they're packed into this
incredibly tight volume.
557
00:31:20,478 --> 00:31:22,679
ROWE: The night sky
inside the galaxy
558
00:31:22,780 --> 00:31:25,549
would look very different
from our own.
559
00:31:25,650 --> 00:31:28,018
PLAIT: On Earth, when you look
at the night sky,
560
00:31:28,119 --> 00:31:30,354
you see a few thousand stars.
561
00:31:30,455 --> 00:31:32,756
But if you were in M60-UCD1,
562
00:31:32,857 --> 00:31:35,092
you wouldn't just see
a few thousand stars.
563
00:31:35,193 --> 00:31:38,195
You would see hundreds of
thousands of stars
564
00:31:38,296 --> 00:31:40,998
in the night sky.
That would be amazing.
565
00:31:47,505 --> 00:31:49,273
ROWE:
As the astronomers look deeper
566
00:31:49,374 --> 00:31:51,909
into the heart
of this tiny galaxy,
567
00:31:52,010 --> 00:31:55,212
Things got even weirder.
568
00:31:55,313 --> 00:31:58,916
They found a supermassive
black hole much bigger
569
00:31:59,017 --> 00:32:01,285
than expected.
570
00:32:01,386 --> 00:32:05,822
It actually has a black hole
that's bigger, five times bigger
571
00:32:05,924 --> 00:32:07,157
than the black hole at
the center of
572
00:32:07,258 --> 00:32:09,192
our Milky Way Galaxy.
573
00:32:09,260 --> 00:32:12,796
PLAIT: When we see supermassive
black holes inside of galaxies,
574
00:32:12,897 --> 00:32:16,199
they tend to scale with
the size of the galaxy itself.
575
00:32:16,301 --> 00:32:19,970
A bigger galaxy has a bigger
supermassive black hole.
576
00:32:20,071 --> 00:32:22,205
Why does such
a tiny little object
577
00:32:22,307 --> 00:32:25,742
have such an oversized
central black hole?
578
00:32:25,843 --> 00:32:27,945
ROWE:
The only possible explanation?
579
00:32:28,046 --> 00:32:32,683
This tiny galaxy
was once much larger.
580
00:32:32,784 --> 00:32:35,752
These galaxies might have
begun their lives as, in fact,
581
00:32:35,853 --> 00:32:37,821
much bigger galaxies.
582
00:32:37,922 --> 00:32:40,290
And that what we see today,
it was really just the very
583
00:32:40,391 --> 00:32:43,293
central, densest part
of a much larger galaxy
584
00:32:44,963 --> 00:32:48,298
ROWE: Based on the size of
its supermassive black hole,
585
00:32:48,366 --> 00:32:51,301
M60-UCD1 may once
586
00:32:51,402 --> 00:32:54,304
have contained many
billions of stars.
587
00:32:54,405 --> 00:32:57,708
Something captured them,
588
00:32:57,809 --> 00:33:00,777
and we don't have to look far
to find the aggressor --
589
00:33:00,878 --> 00:33:03,080
A nearby super galaxy with
590
00:33:03,181 --> 00:33:07,718
lots of gravitational
firepower -- M60.
591
00:33:07,819 --> 00:33:11,321
M60 is a monster.
It has a trillion stars in it.
592
00:33:11,422 --> 00:33:12,689
It's bigger than the Milky Way,
593
00:33:12,790 --> 00:33:14,558
and we're pretty big.
594
00:33:14,659 --> 00:33:17,995
ROWE: The battle was not
a full-on frontal assault.
595
00:33:18,096 --> 00:33:23,367
M60 raided its smaller
opponent, capturing its troops.
596
00:33:23,468 --> 00:33:26,670
SUTTER: This is more of
a stealthy guerrilla hit and run
597
00:33:26,771 --> 00:33:28,271
where we're gonna move in,
598
00:33:28,373 --> 00:33:30,907
pick off some of your troops,
and then get out
599
00:33:31,009 --> 00:33:33,510
before you even notice.
600
00:33:33,611 --> 00:33:36,646
MINGARELLI: All that's left
from one of these drive-by
601
00:33:36,748 --> 00:33:38,015
galaxy interactions
602
00:33:38,116 --> 00:33:41,385
is this supermassive black
hole with a fraction
603
00:33:41,486 --> 00:33:43,453
of its original stars.
604
00:33:43,554 --> 00:33:48,358
ROWE: The conflict
devastated M60-UCD1.
605
00:33:48,459 --> 00:33:51,962
Over 98% of its stellar army
were captured
606
00:33:52,063 --> 00:33:54,431
and became prisoners of war.
607
00:33:54,532 --> 00:33:57,734
SUTTER:
It used to be a big galaxy,
608
00:33:57,835 --> 00:34:00,203
but it suffered
one too many defeats.
609
00:34:00,304 --> 00:34:02,606
And now it's a --
It's a fallen empire.
610
00:34:02,707 --> 00:34:05,075
PLAIT: We can frame this battle
611
00:34:05,176 --> 00:34:09,079
between M60 and M60-UCD1
as just a battle.
612
00:34:09,180 --> 00:34:11,314
But in fact, it's a slaughter.
613
00:34:11,416 --> 00:34:13,417
It's a massacre.
614
00:34:13,518 --> 00:34:17,554
SUTTER: These small galaxies get
all their troops removed,
615
00:34:17,655 --> 00:34:19,322
but the HQ,
616
00:34:19,424 --> 00:34:21,458
the supermassive
black hole remains,
617
00:34:21,559 --> 00:34:24,294
but it doesn't have
any troops left.
618
00:34:24,395 --> 00:34:28,031
ROWE: Eventually, M60 will
conquer its battered opponent,
619
00:34:28,132 --> 00:34:32,569
destroying what's left of
the compact galaxy.
620
00:34:32,703 --> 00:34:34,304
PLAIT: It'll get ripped apart
even further,
621
00:34:34,405 --> 00:34:36,506
and more and more stars
will be consumed
622
00:34:36,607 --> 00:34:37,974
by the bigger galaxy.
623
00:34:38,076 --> 00:34:41,578
So chances are this little
dwarf is eventually going to
624
00:34:41,679 --> 00:34:45,515
be pulled apart and become
a part of M60.
625
00:34:45,616 --> 00:34:48,718
ROWE: In the great game
of galactic warfare,
626
00:34:48,820 --> 00:34:50,687
losing can be catastrophic.
627
00:34:50,788 --> 00:34:53,023
For weak and small galaxies,
628
00:34:53,091 --> 00:34:55,492
resistance is futile.
629
00:34:57,728 --> 00:35:00,530
Pillaged for resource is by
their more powerful opponents,
630
00:35:00,631 --> 00:35:03,333
they slowly become
burnt-out wrecks.
631
00:35:06,003 --> 00:35:11,007
But some peaceful galaxies
face an equally terrible fate.
632
00:35:11,109 --> 00:35:12,909
They starve to death.
633
00:35:24,088 --> 00:35:26,223
ROWE: Cosmic wars are vicious.
634
00:35:26,324 --> 00:35:29,192
They destroy many galaxies,
635
00:35:29,293 --> 00:35:33,463
but violent conflicts can also
give galaxies new life.
636
00:35:35,366 --> 00:35:36,266
Case in point,
637
00:35:36,367 --> 00:35:40,570
galaxy NGC 4485.
638
00:35:41,706 --> 00:35:44,407
HOPKINS: NGC 4485 has a nickname
of the two-faced galaxy,
639
00:35:44,509 --> 00:35:45,742
like the Batman villain,
640
00:35:45,843 --> 00:35:48,612
because it has two
different halves of the galaxy
641
00:35:48,713 --> 00:35:50,080
doing completely
different things.
642
00:35:50,181 --> 00:35:53,150
Half of the galaxy is sort of
old and calm
643
00:35:53,251 --> 00:35:54,517
and relatively quiescent,
644
00:35:54,585 --> 00:35:57,454
whereas half of it appears to
be undergoing a sort of
645
00:35:57,555 --> 00:36:00,423
fireworks display
of new star formation.
646
00:36:01,826 --> 00:36:04,060
ROWE:
Why are new stars only born
647
00:36:04,162 --> 00:36:06,329
in one half of this galaxy?
648
00:36:08,432 --> 00:36:09,733
We found a clue on the edge of
649
00:36:09,834 --> 00:36:14,504
a photo taken by
the Hubble Space Telescope.
650
00:36:14,605 --> 00:36:18,441
It was evidence of an attack
by another galaxy.
651
00:36:18,543 --> 00:36:22,179
We think that another galaxy
passed through it just off
652
00:36:22,280 --> 00:36:24,814
center in a way
that strongly perturbed
653
00:36:24,916 --> 00:36:27,751
the gas on one half
of the galaxy.
654
00:36:29,887 --> 00:36:32,522
ROWE: The two-faced
galaxy skirmish gave it
655
00:36:32,623 --> 00:36:34,090
a gravitational jolt,
656
00:36:34,192 --> 00:36:37,093
forcing clouds of gas together.
657
00:36:37,195 --> 00:36:40,263
When we think of galaxies,
we think of stars,
658
00:36:40,364 --> 00:36:42,032
and of course,
galaxies are made of stars.
659
00:36:42,133 --> 00:36:44,367
But, of course,
gas is the stuff that
660
00:36:44,468 --> 00:36:45,702
stars are made of.
661
00:36:48,172 --> 00:36:49,873
ROWE: When two galaxies collide,
662
00:36:49,974 --> 00:36:51,741
the gravitational
duel can trigger
663
00:36:51,876 --> 00:36:54,077
a huge burst of star formation.
664
00:36:58,349 --> 00:37:00,650
You need something
to give a galaxy a push,
665
00:37:00,751 --> 00:37:03,486
and that's exactly what
a galaxy collision does.
666
00:37:03,588 --> 00:37:06,823
BASRI: And when gas clouds
collide, they compress.
667
00:37:06,924 --> 00:37:10,093
And when they compress,
you get knots in them that can
668
00:37:10,194 --> 00:37:12,696
compress more and form stars.
669
00:37:14,732 --> 00:37:16,533
So you can think of
these collisions as very
670
00:37:16,634 --> 00:37:17,767
violent events,
671
00:37:17,868 --> 00:37:21,171
but ultimately, it can
breathe new life into a galaxy.
672
00:37:21,272 --> 00:37:25,308
ROWE: But the spoils
of war don't last long.
673
00:37:25,409 --> 00:37:28,445
SUTTER: In the short term,
the victor galaxy can
674
00:37:28,546 --> 00:37:31,948
come out glorious with --
With so many new stars.
675
00:37:32,049 --> 00:37:35,352
But this celebration is
short-lived, because that round
676
00:37:35,453 --> 00:37:40,991
of star formation quickly uses
up the material available.
677
00:37:41,092 --> 00:37:44,127
If a galaxy wants to stay
alive, it has to feed on
678
00:37:44,228 --> 00:37:46,162
other galaxies.
679
00:37:46,264 --> 00:37:50,066
ROWE: So galaxies constantly
need to raid new targets,
680
00:37:50,167 --> 00:37:52,602
and that raises
an important question.
681
00:37:52,703 --> 00:37:55,538
What happens if there's
a galaxy just alone in space?
682
00:37:55,640 --> 00:37:58,675
Nothing else is colliding with
it, sort of a pacifist galaxy.
683
00:38:00,244 --> 00:38:03,346
ROWE: The poster child for
these peace-loving galaxies
684
00:38:03,447 --> 00:38:06,216
is NGC 1277.
685
00:38:07,518 --> 00:38:11,321
STRAUGHN: NGC 1277 is
a very peculiar galaxy.
686
00:38:11,422 --> 00:38:15,925
It's pretty big,
and its stars are extremely old.
687
00:38:16,027 --> 00:38:18,461
HOPKINS: It basically hasn't
formed new stars in the last
688
00:38:18,562 --> 00:38:19,963
10 billion years,
689
00:38:20,064 --> 00:38:23,300
so it's kind of the veterans
home of galaxies.
690
00:38:24,368 --> 00:38:26,770
ROWE: NGC 1277 lives in a rough
691
00:38:26,871 --> 00:38:29,506
part of the cosmos called
the Perseus Cluster.
692
00:38:30,875 --> 00:38:35,011
Thousands of other galaxies
surround NGC 1277,
693
00:38:35,112 --> 00:38:38,181
and they are all
ready for a fight.
694
00:38:38,249 --> 00:38:40,016
So you might ask,
why hasn't it had
695
00:38:40,117 --> 00:38:43,119
encounters with other galaxies
that might rejuvenate it?
696
00:38:44,622 --> 00:38:47,691
ROWE: The answer,
once again, is gravity.
697
00:38:47,792 --> 00:38:53,229
NGC 1277 sits inside this
massive galaxy cluster
698
00:38:53,331 --> 00:38:54,564
that has a ton of mass,
699
00:38:54,699 --> 00:38:56,900
and if you look at its
position, it's fairly near
700
00:38:57,001 --> 00:38:58,468
the center of the cluster.
701
00:39:00,805 --> 00:39:03,506
ROWE: The combined gravity
of thousands of galaxies
702
00:39:03,607 --> 00:39:06,109
pulls on NGC 1277,
703
00:39:06,210 --> 00:39:10,513
accelerating it to
two million miles an hour.
704
00:39:13,250 --> 00:39:14,984
STRAUGHN:
And so it has spent the last
705
00:39:15,086 --> 00:39:17,654
few billion years traveling
faster and faster.
706
00:39:17,755 --> 00:39:19,889
Until now, it's almost
at its fastest pace.
707
00:39:22,793 --> 00:39:24,227
HOPKINS:
It's very hard for gravity
708
00:39:24,328 --> 00:39:26,763
to catch it or catch one of
its neighbors
709
00:39:26,864 --> 00:39:30,734
and bring them together to
merge with each other.
710
00:39:30,835 --> 00:39:34,471
ROWE: NGC 1277 has no chance of
711
00:39:34,572 --> 00:39:37,574
grabbing new gas
to make new stars.
712
00:39:37,675 --> 00:39:43,279
It's dying. All that has left
are old red stars.
713
00:39:43,381 --> 00:39:46,649
SUTTER: When it comes
to galaxies, red is dead.
714
00:39:46,751 --> 00:39:49,152
No new stars means no big stars,
715
00:39:49,253 --> 00:39:52,922
no blue stars,
just small dim red dwarfs.
716
00:39:57,962 --> 00:40:01,765
ROWE: Galaxies that don't
fight just fade away.
717
00:40:01,866 --> 00:40:03,466
THALLER: And at that point,
the history of
718
00:40:03,567 --> 00:40:05,502
the universe becomes
really kind of boring.
719
00:40:05,603 --> 00:40:08,171
All the stars will simply
start to die out.
720
00:40:08,272 --> 00:40:09,739
Eventually,
there will be the last
721
00:40:09,840 --> 00:40:11,341
star formed in the Milky Way,
722
00:40:11,442 --> 00:40:13,877
with no new galaxy bringing
fresh material.
723
00:40:13,978 --> 00:40:17,046
Without galaxy collisions,
the universe dies.
724
00:40:17,148 --> 00:40:24,120
♪♪
725
00:40:24,221 --> 00:40:27,090
ROWE:
Galactic battles mix things up
726
00:40:27,191 --> 00:40:29,526
and replenish gas supplies,
727
00:40:29,627 --> 00:40:33,530
and our own galaxy
has reaped the benefits.
728
00:40:33,631 --> 00:40:38,401
Our Milky Way Galaxy
fought a massive battle,
729
00:40:38,502 --> 00:40:41,805
but that battle may have been
necessary to build
730
00:40:41,906 --> 00:40:44,908
solar systems like the one
we live in right now.
731
00:40:48,779 --> 00:40:51,381
ROWE: Clashes with
the Sagittarius Dwarf Galaxy
732
00:40:51,482 --> 00:40:54,517
occurred at the same time
the sun formed.
733
00:40:56,086 --> 00:40:58,321
BULLOCK: It's possible
that we owe our very
734
00:40:58,422 --> 00:41:02,792
existence to the collision with
the Sagittarius Dwarf Galaxy.
735
00:41:02,893 --> 00:41:05,695
TREMBLAY: Maybe the gas
that ultimately gave rise
736
00:41:05,830 --> 00:41:07,764
to the birth of our solar system
737
00:41:07,865 --> 00:41:10,066
once came from
another galaxy entirely.
738
00:41:12,369 --> 00:41:16,339
ROWE: So galactic wars are
both creative and destructive.
739
00:41:17,641 --> 00:41:21,244
Galaxies are built
from collisions,
740
00:41:21,345 --> 00:41:24,280
galaxies survive
from collisions,
741
00:41:24,381 --> 00:41:29,052
and galaxies can also die
from collisions.
742
00:41:29,153 --> 00:41:30,987
Far from being
destructive events,
743
00:41:31,088 --> 00:41:32,689
colliding galaxies may be
the reason
744
00:41:32,790 --> 00:41:34,123
that you and I are here.
745
00:41:37,127 --> 00:41:39,529
ROWE: Intergalactic warfare
has revolutionized
746
00:41:39,630 --> 00:41:44,334
our understanding of how
galaxies live and die.
747
00:41:44,435 --> 00:41:47,804
Ultimately, it's these galaxy
mergers that are one of
748
00:41:47,905 --> 00:41:50,173
the great engines
of all structure growth
749
00:41:50,274 --> 00:41:52,008
in the universe.
750
00:41:52,109 --> 00:41:55,245
OLUSEYI: These collisions
got us to where we are today,
751
00:41:55,346 --> 00:41:58,314
and they're gonna determine
the future of all the universe.
60131
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