Across the universe, there are stellar systems
completely unlike our own
containing two stars instead of one.
Our sun isn't so typical after all.
Even the most fantastical imaginings of Sci-Fi writers,
it doesn't even come close to what nature can produce.
These are binary stars,
and they create some of the deadliest
places in the universe.
Any planet that's close by is gonna get cooked.
But some binaries may have an unexpected trick
up their sleeve,
one that transforms our search for alien worlds.
When it comes to the occurrence of life on a planet,
it may very well be that having two stars
could be a lot better than having one.
Imagine living in the light of two suns.
Are we missing out?
Could two stars be better than one?
Captions by vitac... www.vitac.com
captions paid for by discovery communications
Look at our sky.
You see the same solitary sun rising
and setting day after day.
But throughout the galaxy, alien civilizations
could be enjoying twin sunrises and twin sunsets
because they orbit two stars instead of one.
Half the star systems in our galaxy are binary stars.
It appears to be a common root
of stellar formation and evolution.
So, we can't just focus on the single-star systems
and think we have a complete picture.
The complete picture may include planets
orbiting binary stars...
Alien worlds rooted in Sci-Fi fantasies
that have inspired scientists for decades.
If there is one single event that can most link
to why I became a scientist,
it was going to see the original "star wars" movie,
"episode iv," when I was 7 years old.
And I can remember that scene of Luke Skywalker
standing out on the deserts of Tatooine,
and there's a double sunset.
The music swells up, and I can remember my 7-year-old heart
kind of leaping out of my chest.
That's the moment when I realized I wanted
to be an astronomer.
Could two stars be even better than one?
Living on a planet that orbits a binary system
could be really exciting.
Imagine seeing two stars in the sky every day.
That's pretty cool.
But you know what?
Sometimes it can get too exciting.
Some binary systems
are not places for Sci-Fi adventures.
They're horror stories.
In some cases, the interactions between
binary stars get deadly.
The stars can actually turn on each other.
Binary stars are kind of like siblings.
They're born together and they grow up together.
But sometimes one of those siblings can be evil.
This evil sibling is a pulsar.
It starts life billions of years ago
as the big brother in a binary.
But something transforms it into a monster.
When a large star dies, it will end its life
as a supernova with a crazy big explosion.
And a pulsar is what's left behind.
This big brother's death triggers
one of the biggest bangs in the universe.
In the midst of the explosion, the star's core collapses,
crushing material down into a hyper-dense ball.
Rapid rotation and intense magnetic fields
jump start twin beams of deadly radiation,
and the pulsar comes to life.
The pulsar has to be one of the most amazing monsters
that the universe has ever thought of.
They're only about 10 miles across,
and yet they contain the mass of at least the sun
or even sometimes twice the sun.
The pulsar's sibling
is lucky to live through the chaos
of the nearby supernova.
But it now orbits a brother from hell
in a cosmic no-man's land.
Orbiting a pulsar would be a pretty rough experience
for any object in its vicinity.
Pulsars are spitting out tremendous amounts
of lethal radiation from their poles.
It wouldn't be good to live on a planetary system
near a pulsar because you are gonna be pointed
toward a laser of planetary death.
But these death rays can't last forever.
Within a few million years,
the pulsar spins itself to death.
With its evil sibling dead,
can the other star finally live in peace?
Stars, as I tell students, are a lot like people.
As they age, they tend to expand a bit.
For a single star, it can expand and be as big as it likes.
But in a binary, there's a problem.
Now, this is where the story gets really interesting.
See, you've got your companion star that's swelled up
into a red giant.
Some of that red giant material now can get incorporated
back into the pulsar
and spin it up into something called a millisecond pulsar.
The bloated red giant
can't hold on to its outer layers,
and the pulsar begins to feed.
Matter streams into it,
transferring momentum into the pulsar,
spinning it faster and faster
until it rotates hundreds of times a second.
The beams re-ignite.
Our pulsar is back from the dead once more.
They're dying and resurrecting over and over and over again.
It's like a zombie you just can't kill.
The red giant extends the life of its zombie brother
billions of years longer.
We know of hundreds of millisecond pulsars
scattered throughout the cosmos.
A terrifying thought.
But it gets even scarier.
Some of them are alone.
What's happened to their sibling?
Binary stars are ultimately responsible
for the existence of millisecond pulsars.
They only exist because they've sucked the life
out of their companion stars.
The millisecond pulsars that we see that are all alone
may have just gotten rid of the body.
This is PSR j1311-3430,
a rare breed of millisecond pulsar known as a black widow.
Like its spider namesake, it's deadly,
one of the most massive fast-spinning pulsars
in the universe,
spitting out 100 times more radiation than a regular one.
A black widow pulsar is right on the edge of physics.
Any larger and it would be a black hole.
The intense radiation is amazing.
It's hard to fathom that these things exist.
But generally, the rule is the following with the universe,
which is big and old.
If it can happen, it does happen.
The black widow pulsar is the stuff of nightmares.
Its radiation heats the companion star
to over 21,000 degrees Fahrenheit,
more than twice as hot as the surface of our sun.
It is nothing less than stellar annihilation.
Pulsars are already dramatic, energetic events.
Now you're adding in, "hey, let's destroy a star."
Black widow spiders famously eat their mates,
and that's exactly what a black widow pulsar does.
It actually uses the material from its companion star
to spin itself up,
and then it obliterates it completely.
The companion star vanishes,
murdered by its zombie sibling.
It's the ultimate cosmic ingratitude.
Here you have a companion star
that's brought the pulsar back to life after it's died twice,
and now its entire body is eviscerated
by the radiation of the pulsar
without a speck of dust to suggest it was ever there.
These black widow pulsars
are like the assassins of the galaxy.
Not only do they destroy the star,
they get rid of the evidence.
When pulsars are involved,
two stars are much worse than one.
But could the opposite also be true?
Can two stars create an oasis for habitable alien worlds?
Binary stars offer an exciting possibility...
Alien exoplanets orbiting two stars instead of one.
These binary stars are everywhere,
so the universe could actually be something like
what we see in Sci-Fi movies.
The Tatooine sky could be a real thing.
There could be a planet with life and civilization,
and in the sky, there could be two suns.
What would it be like to live on these worlds?
Could two stars be even better for life?
Our home planet orbits a solitary sun
in a safe region where life could evolve.
Today we're familiar with a very stable,
well-behaved star... Our own sun.
And of course we know there's some solar weather.
Sometimes it throws out high-energy particles
that create the northern and Southern lights,
but it's a very reliable star.
It wasn't always that way.
When the sun was much younger, it was more active,
it was more violent.
Our young sun rotated over 10 times faster
than it does today,
causing its magnetic field to twist and tangle,
sending out huge solar flares.
Solar flares can be very bad for
the habitability of a planet,
particularly if you're very close to the star,
and the reason's because solar flares
essentially represent high-energy radiation.
For example, high-energy protons.
They smash into the atmosphere and they can strip away
gas off the atmosphere.
Picture the early solar system...
Flares and solar storms
attack the atmospheres of rocky planets.
Deadly charged particles can rip them away molecule by molecule.
Without an atmosphere, liquid water cannot survive,
and no liquid water means no life.
In the very early stages, our solar system was an awful place.
The sun was young and highly irregular
and emitting lots of energy in our region.
It took a long time, probably 500 million years or so
before the solar system
calmed down enough to imagine
that anything like life could evolve here on earth.
This is a galaxy-wide problem
for planets orbiting one star.
Take Proxima Centauri, the closest star to our sun.
It's a red dwarf,
the most common type of star in the milky way.
And it even has its own planet named Proxima B.
But Proxima Centauri has not treated its planet gently.
If Proxima B has any liquid water,
it would have to be extremely lucky.
Proxima Centauri would have caused
huge amounts of energy to come out,
and it would effectively strip away
Proxima B of any kind of atmosphere or surface water,
thereby removing any chance of there being habitable world.
The only hope we have left for Proxima B
is a strong magnetic field.
This would surround and protect the planet
from the onslaught of violent energy
that comes out of Proxima Centauri,
and that way, there could still be an ocean,
there could be an oxygen-rich atmosphere,
and perhaps habitable environment,
somewhere where life could have started.
But right now for Proxima B, odds are stacked against it.
Earth's strong magnetic field
protects us from the sun's worst outbursts,
allowing liquid water to survive.
But other planets, like Mars and Mercury,
have not been so lucky.
Solar storms blasted their young atmospheres...
Until they became thin and weak,
snuffing out any chances for life.
But could binary systems actually make things easier,
where planets orbit around two stars instead of one?
Young stars can be very violent and chaotic,
but in the system where there are two stars,
the interaction of those stars can slow down their rotation,
and that means that that violence can be slowed down.
These solar storms can be tempered
so they're not as violent, they're not as frequent,
and if any young planet is formed with an atmosphere,
it can keep it.
So, when it comes to the occurrence of life on a planet,
it may very well be that having two stars
could be a lot better than having one.
Gravitational interactions
can slow down the spin of two close sun-like stars,
giving life the chance to develop.
But not just on one world...
On many planets throughout the system.
With two stars in the middle of a solar system,
you have twice the amount of heat,
twice the amount of light,
and that extends the habitable zone
farther out into the solar system.
For planetary scientist Jani Radebaugh,
exploring systems like this would be a dream come true.
To me, it is so thrilling that worlds like this could exist
and that they might even harbor life.
I mean, there could be a Sci-Fi desert planet like this one
with twin suns, my personal favorite and one
that I can't wait to visit, or if we wanted,
we could just hop over to another habitable planet
and find something completely different.
Galactic backpackers could explore
a variety of Sci-Fi landscapes.
Perhaps alien civilizations are already out there,
living on these habitable worlds.
Two suns could create better star systems than one,
but they could also make things chaotic,
shooting entire worlds into space at hyper speed.
what would life be like
on a planet in a binary system?
Could it be better?
Or is planet earth really as good as it gets?
If you're looking for an abode for life in the galaxy,
we tend to, you know, look for a rather cozy existence out there,
but, you know, it's possible that stars can take you
on a bit of a wild ride sometimes.
Over the past decade,
we've observed mysterious objects
hurtling through the galaxy.
Scientists call them hypervelocity stars.
When we say hypervelocity stars,
we're talking some hyper velocities.
They've been observed moving up to 620 miles per second.
You're talking about something the size of a star, the sun,
an octillion tons of mass or something like that
getting flung away way faster than a rifle bullet.
These hypervelocity stars
start off in a binary system,
but something tears them apart... Something big.
In order to create a hypervelocity star,
you need a very intense source of gravitational power.
Well, the most intense source we know of
is the black hole at the center of the galaxy.
This black hole is Sagittarius a-star.
It is supermassive...
Four million times the mass of our sun.
Two stars stray a little too close,
and the enormous gravity of the black hole pulls at them.
But the star closest feels a much stronger tug,
and this binary system gets ripped apart.
It's a little bit like the Olympic hammer throw,
where the hammer is one star in the binary system
and the Olympian is the other star,
with the cord connecting the hammer
being the gravitational tie
between the binary stars.
If you cut that cord, the other star can go flying off
at very, very high speed.
Once the cord is cut,
the binary stars separate forever.
One is trapped in the gravitational grip
of the black hole.
The other is flung out of the galaxy,
becoming a literal shooting star.
But the star may not be alone.
If a planet is gravitationally bound to a star
and that star gets ejected from the system,
if conditions are right,
that planet can hitch a ride with that star.
Where the star goes, the planet goes.
If you're on planet around a hypervelocity star,
you would be the envy of poets and scientists everywhere
because you would have the most breathtaking view imaginable.
You would start at the very center of the galaxy,
you'll have this beautiful view of the supermassive black hole.
Generation after generation
on this hypervelocity planet
would be treated to thrilling new views of the galaxy.
By the time you're done as you're ejected,
you would see the entire milky way galaxy,
everything, and it would recede away from you
as you moved off into space to who knows where.
Hypervelocity planets just go to show
that the universe is way stranger than fiction.
As we learn more about stars and stellar systems,
even the most fantastical imaginings of Sci-Fi writers,
it doesn't even come close to what nature can produce.
This hypervelocity star and planet
go on the journey of a lifetime,
but what about the stranded companion star,
stuck in the center of the galaxy
next to a supermassive black hole?
It, too, could have a planet orbiting it,
but it's a world living on borrowed time.
If there's a planet orbiting the star that gets left behind
by the hypervelocity star,
so the planet is now orbiting
the star that's orbiting the black hole,
that's not probably gonna last very long.
Typically, the little guy... Pew! Gets shot away.
So it's entirely possible that we have hypervelocity
rogue planets, planets without a star
that are shooting out of the galaxy
at high speed, as well.
But it's not a trip you'd want to take.
Because this world is destined to wander
the emptiness of space forever and alone.
The problem with the planet
is that it's no longer bound to a star,
so the outer surface would most likely freeze.
Binary stars
can create weird environments for planets.
You could get an exhilarating view of the galaxy,
or freeze on an icy wasteland.
But astronomers are finding bizarre new systems
where stars are not being torn apart,
they're being driven together,
creating a cosmic event coming soon to our galaxy.
are two stars better than one?
Binary systems are certainly very dramatic.
There's even one that has two stars so close,
they're touching.
KIC 9832227 is a very interesting binary system.
It's what we call a contact binary.
So this means that the two stars are basically in contact,
but they're separate stars.
They share a common atmosphere or envelope.
One's about a third the mass of the sun,
one about 1.4 times the mass of the sun,
and they're rotating around each other every 11 hours.
2017... Scientists from Calvin college
reveal an exciting discovery.
These binary stars are moving even closer together.
They do the math and make a bold prediction.
So, this star is different from all other contact binary stars
we've studied because this one, we believe,
in the next five years is going to merge,
spiral in together, and explode.
But it's a star close enough to us...
Only 1,800 light years away...
That when it explodes, it'd be bright enough
to see with your naked eye.
Two stars crashing together...
An event known as a red Nova.
If this is true, if you really see it,
it would be fabulous,
because not only would it validate
this amazing prediction,
but we have something new to look at in the night sky.
If this comes through, this would just be
the event of my lifetime.
We don't get to predict too many things in astronomy
except, you know,
"a billion years from now, this thing will happen."
So you have to appreciate what this thing is.
These stars are probably billions of years old.
We're just so lucky to be able to see this right at the end
where we just have a few years left...
A few years out of a billion-year life span.
It's an amazing cosmic coincidence
brought to you by the number three.
Before these stars came into close contact,
they may have had a neighbor...
A distant third star that set this all in motion.
Whenever you have three objects,
the gravitational dynamics becomes incredibly complicated.
The third star pulls on the binary
as the two orbit each other,
stretching them out basically into an elongated orbit.
The two stars resist that,
trying to circularize their orbit again.
That back and forth interaction
pushes the third star further away,
pulls the two stars closer.
The stars have been shoved together,
but their story is about to get even weirder.
Matter will stream off the smaller star
until it is too gravitationally weak to hold its position...
Driving their orbits even tighter together,
moving them faster and faster.
Finally, the smaller star will plunge into the larger one,
tearing through it...
And blasting hundreds of trillions of tons of debris
in every direction.
This would be an enormous amount of energy.
Explosion at its peak will be 10,000 times
brighter than the star is today.
This collision will also be an act of creation.
The cores of the two stars will collide and become one,
creating a super hot blue ball of gas,
a newborn star.
Just think about how cool that is.
In the constellation Cygnus, in about five years' time,
a new star is gonna turn on created from two older stars...
An entirely new way of seeing a star being born.
Around the star,
searing-hot gas will expand outwards,
turning red as it cools, becoming the red Nova.
The explosion will create a brand-new light
as bright as the north star in our night sky.
It's just phenomenal that we get this opportunity.
This is what every astronomer wants to do.
We are at a safe distance
from this colliding star duo.
But would we feel the same way if we were on a planet
orbiting this binary system.
This is a very, very energetic event.
Could life survive such an event?
I wouldn't want to be there as the test Guinea pig.
All this energy comes pouring in,
and your atmosphere is likely to be stripped away.
If there are oceans on this world,
they're likely to be vaporized,
and there may be very little left other than rock.
A Nova is nothing you want to fool around with.
Any planet that's close by is gonna get cooked.
It's gonna get sandblasted, and then, you know, there it is.
If that's the kind of place you want to be,
hey, more power to you, but I like earth.
Earth has a good thing going these days
with our single star.
No collisions, no explosions, no drama.
For two stars to be better than one,
we need to find rocky planets in a binary system.
But so far, we haven't, raising the question...
Can they really exist at all?
The Kepler space telescope
has blown the search for alien worlds wide open,
discovering thousands of exoplanets
orbiting single stars.
But finding rocky planets in binary systems
is proving difficult.
We have found planets orbiting binary star systems,
and that's a big leap forward in our understanding
of how the universe works.
Unfortunately, those planets have all been gas giants,
and they're not really good for forming life.
For alien civilizations to exist around two suns,
they need solid ground.
The hunt for the world of our Sci-Fi dreams
has so far been fruitless.
We always have to consider that maybe rocky planets
around binary stars
just don't exist for some reason that we currently don't know.
And that would mean there would be no Tatooine.
Could paired stars make it impossible
for a rocky planet to form.
If you're a planet trying to form around a binary system,
the gravity in the middle is always changing.
Instead of a single star, you have two stars
orbiting each other.
These two infant stars
start a gravitational tug-of-war.
The material between them is pulled in different directions,
making it harder for bits of rock and dust to stick together.
The system seems too chaotic for rocky planets to form.
The complex gravitational interactions
at play destabilize a lot of potential orbits.
There aren't a lot of opportunities for a young planet
that might want to form to find a stable, long-term home
that lasts for billions of years around that binary system.
It's relatively easy to get ejected or consumed
by the stars themselves.
So, why can't rocky planets survive
when gas giants can?
As any good realtor will tell you, it's all about
location, location, location.
We think that rocky planets tend to form close in around stars
where it's nice and warm, but further out where it's colder,
you have the gas giant planets forming.
So, if you have a binary star system,
it's like a gravitational tornado whipping out
all of that rocky material
so that you're only left with the cold stuff,
which can form gas giants further out.
If a two-star system were a city,
the gas giants are out in the suburbs.
A nice, peaceful spot away from the competing gravity
of the two stars.
Perhaps one-star systems are better than two.
Gas giants aren't great for life,
and those are the planets we're finding in these binary systems.
The very reason that we're here could be down to the fact
that we have one star rather than two.
But in 2017,
a discovery around 2,000 light years away
gives us new hope.
So, as we discover new things in the universe,
we tend to give them catalogue names,
which can be very boring
and very difficult to keep track of.
But SDSS 1557 is worth remembering.
We've seen a binary system that is a white dwarf...
Which is the core of a star like the sun
after it's gotten very old,
blown off its outer layers... That's orbited by a brown dwarf,
an object which is sort of on the border
between a planet and a star.
What's most exciting about the SDSS 1557 system
is that we've found rocky debris.
We see the basic materials,
the basic ingredients are there for forming planets.
This is a really exciting discovery
because we've seen the remnants of asteroids
and rocks orbiting about this ancient binary system,
systems that we thought could've never had surviving
rocky-type things around it before.
This binary system is billions of years old,
and through all that time,
the rocky material hasn't been wiped out.
It has survived.
This is a huge stepping stone to finding our rocky planet
with two suns.
The system provides evidence there's rocky material
close in around a binary star system,
so it's a signpost that rocky planet formation
can occur around binary star systems.
The odds might be longer, but it's still possible.
Could there even still be a planet in this system?
There may still be planetary objects around SDS 1557.
We just haven't seen them yet, but they may still be there.
The search is still on.
A rocky planet orbiting two stars could really exist.
So, for those of us hoping for that Tatooine out there,
that planet with the double sunset,
these debris fields actually give us hope.
Maybe the conditions, at least, are right for the formation
of rocky planets around binary stars.
I think it's out there.
I think finding it is more a question of when than if.
As an astronomer, this is a fantastic time to be alive
at the cusp of discovery.
As a science fiction fan, this is a fantastic time to be alive
because the stuff I read as a kid is coming true.
But perhaps the biggest Sci-Fi fantasy
is much closer to home,
because new research is suggesting something stunning...
Our own sun could have a twin.
A new study in 2017 throws into question
our understanding of the sun.
For the first time now, astronomers are able to peer
inside the clouds that form stars,
and the amazing thing is that the evidence is suggesting
that every single sun-like star forms as part of a binary pair.
The scientists study the Perseus molecular cloud,
a stellar nursery around 750 light years from us,
packed with stars just like our sun.
Many of them are in wide binary systems,
traveling in huge orbits around each other
that span centuries or more.
And all of these binaries are babies,
less than 500,000 years old.
The only way to explain these young systems
is that they formed this way... Not alone, but in a pair.
Just based on statistics and our understanding
of what's going on inside these star-forming clouds,
it is highly likely that the sun formed with a twin.
Perhaps 4.5 billion years ago,
our sun burst into life with a sibling.
Could this twin still be out there
in a distant orbit that we haven't seen?
There was an idea that the sun could have a companion,
which was nicknamed Nemesis,
and this thing would've orbited way far out,
way past Neptune in the solar system.
Scientists searched for this Nemesis star,
but they came back empty handed.
We've looked... we've had telescopic surveys of the sky,
including infrared surveys where these types of objects
would be very bright,
and we've swept the entire sky multiple times
and we've seen nothing.
What happened to our sun's sibling is a mystery.
How do we end up with one star as opposed to binary?
We really don't quite understand.
If it doesn't orbit us now,
it may have left our system long ago.
Over time, some of these binary stars
get closer together and stay together,
and others get ripped apart and lose each other entirely.
It's very possible that our sun, at some point,
had a twin that got ejected.
We don't know exactly when
our sister star was torn away.
It could be clear on the other side of the galaxy
from us by now.
But after everything we've seen in binary systems,
we may be much better off without it.
I'm pretty happy with having just one sun,
so I'm fine to live in this solar system.
A binary sunset would be more beautiful,
but only more beautiful if you were alive.
And yet binary stars
don't just bring death and destruction.
They could also create systems
with a series of habitable worlds.
There's so much we don't know about our own environment
and how it compares to other places in the universe.
It seems like we're in a very lucky place.
The sun is very stable, it's a single star,
we're in a nice orbit around it,
but maybe there are places out there that are even better.
We just didn't even know to ask.
It's certainly possible
that two stars are better for life than one,
but until we find these alien worlds,
it remains an open question.
It's hard to say whether we're lucky or unlucky
to be on a planet orbiting a single star.
It's probably a little boring here
compared to what it would seem like
in these binary star systems.
You know, from a romantic, visual perspective,
I kind of wish we did live in a binary star system.
Can you imagine somebody living on a circum-binary planet
and finding an earthlike planet orbiting a solitary star.
Would they think, "oh, how interesting that would be.
Can you imagine having one sunset?
What would that look like?"
I can imagine them asking themselves
the questions we ask ourselves.
So it's just a matter of perspective, you know?
Grass is always greener on the other side of the binary system.
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