07x03 - The Interstellar Mysteries

[bunniefuu]

narrator: interstellar space is
the space between the stars.

interstellar space is vast,
largely unknown,

and largely unmapped.

narrator: now astronomers
are probing this great abyss

and discovering
something remarkable.

interstellar space is busy.

it's filled with activity.

there are rogue planets that
are not attached to a star.

there are cosmic rays, there
are interstellar gas clouds.

thaller: we've even got
high-velocity stars.

all of that is careening
around out there.

narrator: the greatest secrets
in our universe...

interstellar space
is where we came from.

narrator:
...could lie between the stars.

we live in a small solar system

in the suburbs
of the milky way galaxy --

8 planets and more than
180 moons all orbiting the sun.

in our solar system, the sun
is the sheriff of the town.

we do whatever the sun
wants us to do.

narrator:
the sun's influence stretches
more than one light-year

in every direction

and defines the boundary
of our solar system.

someplace out there is a place
where the sun's influence ends

and the other stars' begins.

that's the entrance
to interstellar space.

¶¶

narrator: interstellar space
is the region

between star systems
in our galaxy.

until now, we've known
little about it.

for so long,
we've thought the space

in between the stars
as entirely empty,

but this turns out
not to be true at all.

durda: there's a lot going on
out there,

and it's the forefront
of astronomy.

narrator: one of the biggest
clues about interstellar space

came right to our doorstep.

¶¶

october 2017.

the pan-starrs1 telescope
spots something unusual.

pan-starrs is an observatory
in hawaii,

and it's scanning
large sections of the sky,

looking for things that change.

all of a sudden, there was
this tiny, little visitor

just screaming
through the solar system.

it was going about
200,000 miles an hour.

wadhwa:
it was a much faster object

than what might be expected
for a solar-system object.

and also its trajectory was such

that it seemed like its orbit
was not bound to the sun.

it was totally unlike any other
path, any other trajectory,

any other orbit
in our solar system.

narrator: astronomers reached
an extraordinary conclusion.

it became very clear that, yeah,

this was not
some solar-system object

falling from a long way away.

this was something
that came from another star,

and i think everybody
was pretty amazed by that.

¶¶

narrator: our first known
interstellar visitor

on a fly-by
through our solar system.

it was the very first object
that we had ever discovered

that had originated
outside the solar system.

everything else we've seen --
every comet, every asteroid --

originated within
our solar system.

wadhwa:
a big, mega solid object

entering in
our own solar system,

that's something that, you know,
i can only dream of

but had never thought
it would actually be a reality.

¶¶

narrator: scientists
named the object 'oumuamua,

hawaiian for "a messenger
from afar arriving first."

this thing came from
interstellar space

into our solar system,

and the main question is,
what could it be?

¶¶

narrator: the object's shape
was mystifying.

it's almost sort of shaped
like a cigar.

it's 10 times longer
than it is wide.

walsh:
and this is extraordinary.

there's no object in our
solar system

that we've ever measured
that is this elongated.

narrator:
'oumuamua looked so unnatural,

it sparked
scientists' imaginations.

one of the things to remember
about scientists

is that we're still
human beings.

we have read science fiction.

we have imaginations.

plait: i have to admit,
when i first heard about it,

my first thought is that
it was rama from

an arthur c. clarke story,
"rendezvous with rama."

this is a very
elongated spaceship

that came from another star.

loeb:
it reminded me of some designs

we had for
interstellar space crafts

that have to be much longer
than they are wide

in order to minimize friction
with the interstellar gas.

narrator:
could 'oumuamua be an alien
interstellar spacecraft?

¶¶

astronomers,
including professor avi loeb,

took the idea seriously.

loeb:
we decided to follow this object

using the best telescopes
in the world

and observe whether there is
any radio transmission from it.

narrator: astronomers hunted for
signs of alien communication.

[ static ]

but after eight hours
of listening

across multiple
frequencies, nothing.

sadly, no emissions
were detected.

it's almost certainly
a natural object.

i would bet
all of my money on that.

i was disappointed.

i would've been
much more excited

if we had found evidence
for an alien civilization.

narrator:
no little green men this time.

'oumuamua is a natural object.

but what exactly is it?

at first, observers thought
it might be a comet.

something that's mostly ice
with a little bit of rock.

those are the sorts of bodies

that exist really far out
from the star

and are the easiest
things to eject.

narrator: but a comet passing
this close to the sun

would warm up,

turning the ice into a gas,
forming a vapor trail.

on 'oumuamua, astronomers saw
no sign of this happening.

there was no fuzziness around it

that you would expect
from a comet

as the ice
was turned into a gas.

wadhwa:
it was really mysterious,

and so everybody
who was observing it

thought it was an asteroid.

narrator: as team's track
'oumuamua across the sky,

there was an unexpected twist.

as 'oumuamua passed through
our solar system,

basically, it was falling
in toward the sun,

speeding up immensely
as it passed the sun,

before exiting the solar system

in almost
the opposite direction.

plait: but then something
weird happened.

as it was moving away
from the sun,

it was slowing down
as you'd expect,

but it wasn't slowing down
fast enough.

narrator: 'oumuamua gets a boost
through our solar system,

but how?

so we think the reason
is that it's outgassing.

plait: in other words, it was
emitting a little bit of gas,

and that was acting as
a little bit

of a rocket-motor push on it.

walsh:
it's kind of like a little
jet engine on the surface --

just gives it
a little thrust over time.

narrator: this tiny nudge
reveals 'oumuamua's

true identity.

so, in that case, it is looking
more like a comet.

it's just that that emission
wasn't enough to see.

¶¶

narrator: powered by outgassing,
this interstellar nomad

might travel from star to star,

but figuring out
where in the galaxy

it came from
just got more difficult.

now that we know
'oumuamua has outgassed,

which changes its velocity
and changes its trajectory,

it makes it much harder
to do that.

narrator: 'oumuamua may now be
safely racing away,

but the solar system
faces bombardment

from another interstellar
source f*ring at earth

at close
to the speed of light.

cosmic rays are the b*ll*ts
of the universe,

and they are flooding
interstellar space.

¶¶

narrator: 'oumuamua's surface
tells the story of its journey

through interstellar space.

radebaugh: the interesting thing
about 'oumuamua is its color.

it's actually red.

i'm standing on a surface
that's a nice analogue

for the surface of 'oumuamua.

as you look around,
you see a really dark,

kind of shiny coating
to all of the rocks,

and it extends up the valley

and even onto
the mountains behind me.

narrator: scientists think
'oumuamua's red sheen

comes from tholins,

organic molecules that are
the building blocks of life.

how cool is it that something
came out from some other origin,

passed through
our neighborhood,

and it possessed
some sort of organics?

that could be a possible
gold mine for us.

narrator:
in our own solar system,

distant objects like comets
and asteroids

also carry tholins.

this happens because
their surfaces are bombarded

by cosmic rays
and that changes the nature

of the chemicals on the surface.

so we think the same thing
has happened to 'oumuamua.

it's been out there
in interstellar space

and been bombarded
by cosmic rays over the eons.

narrator: galactic cosmic rays
are high-energy particles

that tear through the universe.

¶¶

interstellar space is filled to
the brim with these cosmic rays.

things like protons and
electrons or perhaps

some heavier,
the more exotic particles

that are literally whizzing
through the universe.

some cosmic rays
can travel as fast

as 99% the speed of light --

incredibly fast,
energetic things.

narrator:
it takes a lot of energy

to accelerate anything close
to the speed of light.

cosmic rays come from
many energetic and powerful

and violent sources
in our universe.

everything that's big and
blasting generates cosmic rays.

narrator:
one of the most powerful
cosmic-ray generators

is the death of a giant star,
a supernova.

¶¶

a supernova is
a really energetic expl*si*n.

it's so energetic
that it can create all kinds

of interesting things.

narrator: when a star runs out
of fuel, it collapses.

the mass of the star
crashes inwards,

triggering a huge expl*si*n.

¶¶

the shock wave slams
into surrounding gas,

amplifying magnetic fields.

plait: if you get a particle
caught in there,

trapped in the magnetic fields
of this gas,

it can bounce back and forth,
be accelerated very rapidly.

it goes ding, ding,
ding-ding-ding-ding.

like that.

narrator: eventually,
the particle moves so fast

that the magnetic field
can no longer hold it.

and, pyew, it gets sh*t out
at very near the speed of light.

narrator: cosmic rays have mass,
and they wreak havoc.

cosmic rays are the b*ll*ts
of the universe,

and they are flooding
interstellar space.

but, thankfully,
we're protected.

¶¶

narrator: cosmic rays from
interstellar space battle

with another superpower --

our own bodyguard
in the solar system -- the sun.

thaller: we think of the sun
as the source of energy

and warmth for earth,
the giver of life,

but it's also
protecting us in ways

you might not be aware of.

narrator: the sun emits a stream
of charged particles

called the solar wind.

the particles hurtle out
past the planets

at more than
a million miles an hour.

but they do eventually
run out of power.

there's this region where
the solar wind grinds to a stop.

it's plowing into this material
between the stars

and eventually slows and stops.

narrator:
the solar wind carries the sun's
magnetic field with it,

forming a bubble
around our solar system.

we call that the heliosphere,
"helio" for the sun

and "sphere"
for this giant magnetic field.

plait: it acts, basically,
like a shield,

protecting us from
these galactic cosmic rays.

if that weren't there,

the radiation levels hitting the
earth would actually increase.

thaller: so, in a real way,
the sun is protecting us

from the dangerous environment
of interstellar space.

narrator:
the heliosphere protects us

from the majority
of cosmic rays,

but some still make it
into the solar system.

fortunately for us, earth also
has its own defense mechanisms.

we have our magnetic field
that can redirect

the lowest energy cosmic rays,
and we have our nice,

thick security blanket
of an atmosphere,

which absorbs most of
the high-energy cosmic rays

before they even get a chance
to reach us here on the surface.

¶¶

narrator: cosmic rays from
interstellar space

can alter dna
and cause diseases.

but without them,
we might not be here at all.

even that tiny fraction
of cosmic rays

that makes it
through our atmosphere

to the surface of the earth

can have a profound influence
on the evolution of life.

narrator:
cosmic rays can damage the dna

that carries
the information of life.

when those molecules
are broken apart,

the atom is altered
by collisions with cosmic rays.

the information carried
is changed.

that's a mutation.

that's what drives
natural selection.

so life and we ourselves
are deeply connected

to interstellar space around us.

narrator:
but interstellar space is also
home to much larger objects,

objects that could wipe
out life all together.

¶¶

narrator:
our solar system races around
the center of the milky way

at 143 miles per second.

at its center, the sun,

just 1 of around 200 billion
stars in our galaxy.

we're not living in
an isolated bubble

all on our own here
in the galaxy.

we're living in a swarm,
a neighborhood of other stars.

narrator: and the movement
of all these stars

can have far-reaching effects
on our solar system.

beyond the planets
and our heliosphere...

lies the oort cloud

right on the border
of true interstellar space.

the oort cloud is the remnants
of the formation

of the solar system --
small, icy, dirty bodies,

aka comets.

narrator:
the comets in the oort cloud

are so far out they're only
weakly bound to the sun.

they spend most their lives
perfectly happy,

orbiting the sun lazily
in their frigid depths,

but every once in a while,
they can be perturbed.

narrator: our sun is moving
through interstellar space,

and so are other stars.

as our sun orbits the galaxy

and encounters
other stellar neighbors,

inevitably,
there is going to be one

that's going to pass through
or near our oort cloud.

narrator:
the gravity of a nearby star

could disrupt the oort cloud...

sending showers of comets

barreling through
the solar system.

some of them could strike earth.

¶¶

¶¶

thaller: comets falling down
into the inner solar system

is something that we really want
to pay attention to,

that could actually be dangerous
to life here on earth.

so one of the things we do
is look out into the galaxy

and see if any stars
are gonna be coming nearby

anytime in the near future.

narrator: with a new space
observatory called gaia,

astronomers keep watch over
millions of neighboring stars

in our galaxy,

tracking their movements
through interstellar space.

so what's the next star
that's gonna pass the earth?

and it turns out we may know.

there's an orange dwarf.

it's called gliese 710.

narrator:
in 2018, new data shows

gliese 710 is on
a collision course

with our oort cloud.

it's gonna kick up
a lot of dirt,

kick up a lot of dust,

and it might be bad news
for the inner solar system.

we might get a lot
of unwanted visitors.

¶¶

narrator: luckily for us,
gliese 710 won't arrive

for another 1.3 million years.

but there are other
rogue stars out there.

all the stars
that you can see in our sky

plait: are in the disc
of the milky way galaxy,

and they tend to be moving
in the same direction

at about 100 miles per second
around the center.

narrator: gaia discovers stars
that follow different rules.

they don't seem to be
moving around

with the motion of the galaxy.

instead, they're actually
flying through space.

plait:
and they are screaming.

these are cannonballs.

they're moving, three, four,
five times faster

than the other stars
in the galaxy,

and they tend to moving away
from the center.

narrator:
these cosmic cannonballs are
known as hypervelocity stars.

what could cause them
to move so quickly?

some of these stars originated
from binary star systems

in which one of the components
went supernova,

removing that gravitational tie
to the other star,

allowing that star to escape

and basically be ejected
through the galaxy

on its own very, you know,
high-speed trajectory.

narrator: some hypervelocity
stars have a darker past.

they're flung from a black hole.

there are trillions of
black holes in the universe.

narrator: there are giant
black holes at the centers

of nearly all large galaxies,
including our own.

and these monsters inflict chaos
on paired stars.

again, you have
a binary system of stars,

and they are orbiting
the back hole

in the center of our galaxy.

when they get too close,

one of the stars falls
into the black hole,

and the other one
is ejected away at high speed.

narrator: these hypervelocity
stars blaze through

interstellar space.

their stellar winds
can bring beauty out of chaos.

a lot of these
hypervelocity stars

that we see are
very massive stars,

much larger and hotter
and more luminous than the sun.

well, as they're plowing
through the material

in between the stars
their wind is expanding

and slamming
into the gas and the dust.

and so what you see
when you look at them

is this beautiful arc,
like the bow wave off of a ship.

and we have images of these,
and they're gorgeous.

these are beautiful,
beautiful patterns.

narrator: hypervelocity stars
paint the canvas

of the universe.

it looks serene,

but interstellar space
can be anything but tranquil.

¶¶

it's no man's land.
it's the wild west.

there are no rules.

you can do whatever you want.

narrator: in the badlands of the
galaxy, outlaws reign supreme.

¶¶

¶¶

narrator: tens of light-years
from the sun,

mysterious objects
lurk in the darkness.

we've only seen a fraction
of the stuff that's out there,

you know, so this is really
the next great frontier.

narrator: in 2016, scientists
spot a tiny source

of infrared light
95 light-years from earth.

¶¶

it's too dim to be a star
and not orbiting a star either.

it can only be a rogue planet.

when we think of a planet,
we think of an object

that's orbiting a star.

in fact, that's the very
definition of a planet today.

well, what if it doesn't
orbit anything?

we call those rogue planets.

¶¶

narrator: the following year,

astronomers take
more detailed images.

they find it's not just
one world but two.

plait:
and that's incredible, right?

there's this object
out in the middle of space.

they're not orbiting stars.

these are rogue planets
orbiting each other.

narrator: planets with 4 times
the mass of jupiter

over 300 million miles apart,

more than 3 times the distance
between the earth and the sun,

they circle each other
once a century.

think about not just
one rogue planet

but a binary rogue planet,

two planets
circling around each other.

they may still be gas giants,
like jupiter,

and if that's the case,
they don't have a surface.

but if they're really old,

they could actually have
had enough time to cool

and maybe they do
have a surface.

we don't really know,
but they would be very dark.

there's no star nearby
to light them up.

narrator: rogue planets drift
in eternal darkness

through the frigid expanses
of interstellar space,

untouched by light
for millions of years.

let's say you found yourself
standing on the surface

of one of these rogue planets.

i mean, it would be
such a bizarre sight.

there wouldn't be a sun.

you know, it would just be
the night sky all around you.

durda: think about the darkest,

moonless night you can possibly
imagine here on the earth.

that's the light level
that you have out there

in interstellar space.

narrator: physicists now believe
there could be billions

of rogue planets in our galaxy,
one for every four stars.

the question is, why do these
rogue planets exist at all?

did they form freely,

or were they somehow cast out
of their solar system?

the answer is probably both.

¶¶

narrator: some rogue planets
formed from lumps of gas

that never quite became stars.

others formed like planets

around a star in solar systems
like our own.

when solar systems are formed,
they're violent places.

sometimes planets just crash
into each other

and become a single object.

but sometimes
there are near misses,

and they'll scatter away
from each other and be ejected.

so these rogue planets spend
almost their entire lives

completely alone.

¶¶

narrator: without a star
to keep them warm,

rogue planets seem to be
an unlikely place for life.

a rogue planet on its own
out in space,

probably not gonna be habitable.

it's cold out there, right?

so if it's the size
of the earth,

it's probably a frozen ball.

narrator: but in 2018,
astronomers announced that life

could be possible
on a moon around a rogue planet.

there are icy moons orbiting
jupiter and saturn

that are heated by the gravity
of the planets they orbit.

it has nothing to do
with the sun.

narrator:
as these moons are warped
by the planet's gravity,

friction generates heat
that keeps the water liquid.

so it's entirely possible
that if a rogue planet

was able to keep its moons
and these moons are icy,

they could have liquid oceans
under their surface.

they don't need a star.

they've got their planet
keeping them warm.

¶¶

narrator: interstellar space
is far from empty.

it's loaded with disconnected
bodies that don't have a home.

you can think of
interstellar space

as almost sort of
a cosmic pinball machine.

you've got high-velocity stars.

you've got rogue planets.

you've even moons that have been
thrown out from around planets.

all of that is careening around
out there.

interstellar space
is more active and alive

than we ever imagined.

as it turns out,
it even has clouds that sing.

¶¶

¶¶

narrator: hundreds
of light-years away,

vast amounts of gas

and dust drift
through interstellar space.

think about all that space
between the stars,

full of gas, dust --

full of the stories about
how stars and planets formed.

we've been missing a lot.

narrator:
scientists call the gas and dust

between the stars
the interstellar medium.

it's the most common stuff
out there in the galaxy.

it's hydrogen atoms, a few
helium atoms here and there.

¶¶

narrator: the interstellar
medium isn't distributed

evenly throughout the galaxy.

it's patchy.
it's clumpy.

and there's some regions
that have more stuff,

and some regions
that have less.

narrator:
the regions with more stuff
are called interstellar clouds.

an interstellar cloud
is really just

a slightly
denser concentration of gas

and possibly dust that we see
scattered across our galaxy.

narrator: interstellar clouds
can stretch vast distances

across the cosmos --

some reaching a million times
the mass of the sun.

you know, it boggles my mind

when i look at these
interstellar clouds

and realize that they're
light-years in size.

¶¶

narrator: interstellar clouds
are more than just clumps

of gas and dust.

they're alive.

scharf: we know that these are
places where stars form,

and they're also places
that are, themselves,

formed by dying stars.

¶¶

narrator: stars form when
an interstellar cloud collapses.

gravity pulls matter together,
igniting the core.

¶¶

but astronomers
don't have a full

understanding of the process.

understanding the shape
and structure of a cloud

like this is important
to understanding

the process
of star formation.

some shapes and structures
just aren't big enough,

in some dimensions,
to allow a cloud to collapse.

everything we can learn
about this sort of thing

really depends on its shape.

so knowing that shape is the key
to understanding it.

narrator: but there's a problem.

when we look out
into the universe,

we're seeing everything
projected onto the sky.

so we may look at the structure
like an interstellar cloud

and have very little
information about its depth.

that's one of the big
challenges for astronomers,

is to decode the full
three-dimensional shape

of these clouds.

narrator: in 2018,
scientists get a breakthrough

in their efforts
to understand star formation.

around 490 light-years
from earth

lies an interstellar cloud
known as musca.

it looks like a thin snake.

durda:
optically, this dark doodle,

if you will,
looks like a dark cloud.

it looks rather two-dimensional,

silhouetted against
the background stars on the sky.

narrator: astronomers
examine musca in infrared,

and discover it's singing.

it vibrates,
and it sets up waves

that move through this cloud,
back and forth.

and these are called
magnetohydrodynamic waves,

which sounds awesome.

narrator: the team converted
the waves into musical notes,

producing musca's song.

¶¶

¶¶

it turns out that,
if you study this,

you can actually determine

the three-dimensional
shape of this cloud

by the way the waves
move through it.

[ string resonating ]

it's a little bit like listening
to the frequency of sound

coming from some instrument
that you don't see,

and trying to reconstruct
what kind of an instrument

that must be.

¶¶

narrator: a low notes tells you
you're listening

to something large,
like a cello,

while a high note represents
something smaller,

like a violin.

and just as different
instruments

make very different sounds,

clouds with different structures
will vibrate in different ways.

they'll "sing" different songs.

durda:
the sounds, if you will,

the frequencies coming
from that cloud,

are a clue ultimately
to its shape and structure.

plait:
and with this musca cloud,

even though it just looks
like a line in the sky,

astronomers were able
to determine its 3-d shape.

and it's not just a filament.

it's actually a disc.

it's like we're seeing
a disc edge-on.

¶¶

narrator: musca is more
of a pancake than a snake.

we've just been looking
at the pancake from the side.

plait: that's amazing.

it's like putting on 3-d glasses
for the first time

and finally seeing depth
in the universe.

¶¶

narrator:
the same technique can be used

to study other
interstellar clouds.

durda: it brings with it a whole
new wealth of knowledge

on the structure and processes
that are going on there.

¶¶

¶¶

narrator: we're discovering
that the interstellar space

in our galaxy is full of stuff,

but something
doesn't quite add up.

it turns out that if we take
all of the matter

we see around
the universe today

and add it up, it doesn't
equal the total amount

that we know must be there.

narrator: 1/3 of the matter
in the universe is missing.

so where is it?

to find it, we have to look
beyond interstellar space

into the dark, mysterious
reaches of intergalactic space.

¶¶

¶¶

narrator: the milky way is one
of trillions of galaxies

in the observable universe.

the milky way galaxy is a disc.

it's about
100,000 light-years across.

it's filled with stars, lots
of planets, and gas and dust.

narrator:
but where does our galaxy end

and the other galaxies begin?

a structure like our galaxy

doesn't really have
a hard edge to it.

it actually becomes less
and less dense,

and it gradually peters out
as you move

into true intergalactic space.

narrator: between the galaxies
are huge gaps --

intergalactic space.

but, like interstellar space,
this region isn't empty.

¶¶

new research reveals, it holds
the answer to a major mystery.

we know how much normal matter
was made in the big bang.

and we can look around us today

and count up all
the normal matter we see,

and the problem is,
they don't equal up.

narrator: there's something
wrong with the galaxies

in our universe --
they're not massive enough.

about 1/3 of the normal matter
in the universe is missing.

there is more normal matter that
is not bound inside of galaxies.

so where is it?

one idea for where this missing
normal matter could be,

is that it's actually
floating outside of our galaxy

in a hot gas.

narrator: scientists suspected
this hot gas

might exist in long strands
between the galaxies,

but the gas is so thin
and diffuse,

it has been hard to detect...

until now.

¶¶

in 2018, astronomers study
a bright distant quasar

called 1es 1553.

a quasar is when
a black hole feeds.

it gives off light,

and we can see it all the way
across the universe.

narrator: the quasar's light
takes over 4 billion years

to reach us,

but observers notice
something unusual.

something is absorbing the light

as it passes
through the universe.

the culprit?

ghostly strands of gas

suspended in the spaces
between galaxies.

these results suggest
that a good fraction

of the normal matter
in our universe

is not enclosed
inside of galaxies.

they don't live
in the city limits.

instead, they live in long,

thin streams that connect
the galaxies together.

¶¶

narrator: heated by shock waves
to millions of degrees,

these strands of gas
could extend

throughout the universe...

and account for the matter

that's been missing
all this time.

¶¶

this opens up
a very interesting question --

has this matter
always been there

and just failed to accumulate
onto the galaxies,

or was it started in galaxies
and gets blown out?

we honestly don't know.

¶¶

narrator: interstellar space,

and now intergalactic space,

are more alive than we thought.

from rogue planets

to singing clouds of gas,

interstellar space
is stranger than fiction.

and we've only just begun
to tell its story.

just because
there's so much we don't

understand
about interstellar space,

it makes it that much
more critical to explore

and try to figure it out.

durda: there's more to find out
about interstellar space

than what we know,

and that's the beauty
of exploration

and the beauty of knowledge,
is it's ever-expanding,

and that frontier
is always there.

plait: who knows what else
is out there?

what else could be lurking out
in the dark,

between the stars?