All language subtitles for BBC.The.Sky.at.Night.2017.Ep.05.Into.the.Dark.Zone.1080p.HDTV.x264.AAC.MVGroup.org

We've been observing the planets
with telescopes

for hundreds of years and sending
probes out into space for over 50.

So you might have thought that
our cosmic neighbourhood would be

pretty well explored.
But the truth is,

we've only just
scratched the surface.

The reality is
that most of the Solar System
still remains a mystery.

Once you head out beyond Neptune,
you enter a realm that was,

until recently,
almost completely unknown.

Yet we now know that it's full
of extraordinary objects.

So tonight we're going to explore
this unknown area.

We're going to venture out
into this dark zone.

Since Pluto's relegation
to dwarf planet status,

the planets of the Solar System
now end at Neptune.

And if you think
that all the exciting stuff

happens between there and the Sun,
you're totally mistaken.

We now know that that dark realm
beyond Neptune's orbit is filled

with a vast number
of strange icy bodies.

And, as we've discovered them
over the last couple of decades,

it's become clear
that they play a critical role

in the evolution
of the whole Solar System.

Tonight, from
the Observatory at Herstmonceux,

we'll explore the incredible objects

that we're finding
in the outer Solar System.

Some are on uniquely
baffling orbits,

while others spin
surprisingly rapidly.

And Marcus du Sautoy investigates
the surprising mathematical laws

that govern these objects, and how
they reveal that our Solar System is

potentially on the brink
of catastrophic instability.

This group of strange new worlds
needed a name,

and we call them
the Trans-Neptunian Objects.

But to understand the role
they play in the Solar System,

you really have to see them
in context.

Let me paint you a picture
of our Solar System.

At the centre, we have
our local star, the Sun.

Then, the inner planets.

Mercury, Venus,

Earth, which of course we're on,

and then, a little beyond, Mars.

Then we move on
to the outer planets.

Jupiter, Saturn.

Over here is Uranus.

And way over here is Neptune.

4.5 billion kilometres
away from the sun.

Now, the images of the planets
aren't drawn to scale,

but the distances from the Sun
are about proportional.

Except this isn't the outer edge.

Not by a long way.

Because beyond is the realm of
the Trans-Neptunian Objects.

Most are in a region
called the Kuiper Belt.

Pluto, for instance, is here.

One called Haumea is here.

Another, called Eris, sits here.

And some are even further out,

or in strange orbits outside
the plane of the Solar System.

The Kuiper Belt alone is huge,

some 16 billion kilometres wide.

It forms a flat disc, lying
in the same plane as the planets.

And within it are hundreds
of thousands of new objects,

maybe millions.

Trans-Neptunian Object hunter
Michelle Bannister has been using

some of the most powerful telescopes
in the world

to search through this dark zone.

She tells Chris about some of
her most exciting discoveries.

Well, the outer Solar System is
a fascinating and interesting place,

but what's been found recently?

Well, we've just wrapped up one
of the largest surveys ever made

of the outer Solar System, and we've
been able to double the number

of Trans-Neptunian objects orbiting
outside Neptune, that are known,

that have really well understood
orbits.

We've been able to discover
more than 800 icy worlds,

little objects about 50 to maybe
300 or so kilometres in size,

most of them,
that orbit beyond Neptune.

These are leftover pieces,
planetesimals,

from the formation and evolution
of the giant planets.

Just very excited, I've got

a picture of one of
your discoveries here.

This goes by the delightful moniker
of 2015RR245.

So RR245, it's a lot bigger than
some of these others.

This is bright,
this is really bright,

and when we found it,

it's moving across the sky
over three hours

in these three images
you see here,

really slowly,
and because it's bright and slow,

that means it has to be
very far away.

It turns out
it's about 700km across.

It's one of the 20 largest dwarf
objects in the outer Solar System.

So, what's a world like this
actually like? What's it made of?

What would it be like to be there?

What you probably would see
is a surface of complex ices.

Definitely water ice.

On Pluto, we know that
water ice makes mountains.

So here maybe you'd see terraces

and small mountains
of some water ice.

You'd also see
reddish layers on the surface.

And that's because RR245 is probably
large enough that it has

some of the complex molecules
that form on icy surfaces over time,

from hydrocarbon molecules
being bombarded

by the slow rain of cosmic rays.

So, I've got a picture
of one of my favourites.

This is an artist's impression
of Haumea,

which is one of the first
to be discovered.

Yes, it was discovered back in 2003,

and we now know a lot more about
this wonderful icy world,

this is one of the strangest objects
in the outer Solar System.

It's shaped in this elongated way,
like a rugby ball,

cos its spin axis is actually here.

So it's spinning like this,
and it spins every 3.9 hours or so.

That's really fast.
These are big things.

It's one of the fastest things
in the Solar System, spinning, yeah.

This is spinning so fast
that the solid rock itself

that makes up most of this object
is actually flowing out,

and that gives it
this elongated shape.

How are they arranged?
Some of them are in a flat disc,

so they have round orbits
that are flat.

These are probably the ones
that have changed the least

since the formation of the
Solar System in the Kuiper Belt.

Then you have ones
where their orbits have been

dynamically changed,
so they're actually excited,

they have tilted orbits
out of the plane of the System.

Not a whole lot, but, you know,
a few tens of degrees.

What are the big new discoveries
still lurking out there?

There's some fun indications that
we could have another dwarf planet

out beyond Neptune,
that we haven't yet found.

This could be as big as
a Mars-sized object,

and this ties into an object

that was found
about a year and a half ago now,

by a different survey in Hawaii.

And this object,
it actually orbits perpendicular

to the plane of the Solar System.
Oh, is it called Niku?

It's called Niku.
OK, I was going to talk to you.

There's Niku in all its glory. Yes!

I have to say,
it doesn't look like much.

It's got charisma. All right,
we'll go to the theory.

There you go, there's the theory.

We've watched this object move
across the sky for several years,

and therefore able to do
the computation of its orbit

and show this orbit is strange.

So, this is Jupiter, Saturn, Uranus,
Neptune, all in a plane,

and the Earth would be in this plane
as well. Right.

But this object orbits perpendicular
to the plane of the Solar System,

and this is a mechanism
that we don't have a clear idea yet

of how to form orbits like this.

You can make a comet
that goes way out,

and then comes back in
on such a perpendicular orbit,

but making something that's
relatively small and close...

This dips in amongst the giant
planets, and then zips out as far as

the Kuiper Belt. Except the Kuiper
Belt's over here, it's, you know,

in a nice, relatively even disc.

Nothing does this
in the Kuiper Belt.

Every time I talk to anyone
who studies the outer Solar System,

I end up with more questions,
so I hope you find more things,

I hope you come back
and tell us about them.

Thank you very much. Thank you.

The more we peer in
to this dark zone beyond Neptune,

the more mysteries we discover.

For most of astronomical history,

these Trans-Neptunian Objects
have been hidden

from even the most powerful
telescopes,

and that's why they've never got
the attention they really deserve.

But these days,
are they so impossible to spot?

To find out,
we set Pete Lawrence a challenge -

to try and see a Trans-Neptunian
Object using amateur equipment.

I've been given tough challenges
on The Sky At Night before,

but this one has to be up with
some of the hardest I've ever had.

These objects are, after all, tiny,
dark and a long, long way away.

But I've decided
to try and observe Haumea.

The reason I've chosen
that particular one

is that it's really well placed
at present.

It's actually located
just between the midpoint,

or just south of the midpoint
between the stars

Arcturus and Muphrid,

and both of those stars are
in the constellation of Bootes.

I know the exact position of Haumea
because I've looked it up

on the JPL Horizons
Ephemeris Generator.

That's a free online resource.

And I can tell you, it's pretty
faint, it's about magnitude 17.6,

which is about 36,000 times fainter

than the faintest star
you can see with the naked eye.

To attempt this observation,
I'm using my 130mm telescope,

with a DSLR camera
and my laptop to process the images.

We are trying to capture this
very close to the June Solstice,

so the sky is still really bright.

In fact, the threshold of brightness
is too high, really,

to pick out anything really faint.

It's a little bit frustrating
because I'm confident

that under darker skies,
for instance, later in the year,

I'd be able to make this work.

I did have an inkling this was going
to happen, so a month ago,

I did dial into a remote telescope
set-up in New Mexico.

This is a commercially available
telescope

that anyone can book time with
on the internet.

The one I'm using
is actually smaller than mine,

but the skies in New Mexico
are fantastically dark.

And these are the results.

Well, looking at the New Mexico
results, they're much clearer,

those dark, transparent skies
have really worked for us.

But how am I going to find Haumea
amongst all those stars?

Well, I'm going to use
a classic technique

which is known as the blink method.

So, the blink method works
like this.

The object I'm looking for
will move over a period of days.

So if I take a picture on one day
and then wait a few days,

take another picture,

and then I align the stars
between those two pictures,

and then blink between them,

anything that moves should
stand out like a sore thumb.

This is the same technique
that was used in the 1930s

by Clyde Tombaugh to spot Pluto.

And these are the images
he took over a week

that eventually revealed
Pluto's existence.

Hopefully, that same technique
should work for me.

And there it is! I can see it,

I can see the dot moving
backwards and forwards.

Now, that represents the movement
of Haumea over six days.

So the blink method has worked.

That's incredible, isn't it?
I mean, that's an object which is

just a few hundred kilometres
across,

and about 7.5 billion
kilometres away.

That's amazing!

If you'd like to try and spot
a Trans-Neptunian Object,

we've put some information
about the positions of Haumea,

Makemake and Niku on our website.

And please do drop us a line
to let us know how you do.

It's not just our instruments
that have improved.

We now get much more information
about objects in deep space

from missions like New Horizons.

Three, two, one...

We have ignition and lift-off of
Nasa's New Horizons spacecraft...

Nasa's space explorer, New Horizons,
reached Pluto in 2015,

and it's still exploring, venturing
deeper into the Kuiper Belt.

It revealed new information about
both Pluto and its moon, Charon.

It found unexpected warmth on Pluto

and a mysterious dark red area
on Charon's North Pole.

Maggie spoke to New Horizons
team member Carly Howett

from her base in Colorado, for the
latest updates on these mysteries,

and to see where they're going next
in this dark zone.

Hi, Carly, good to see you again.
Yeah, you, too. Good to be here.

Now, last time we spoke,
it was incredibly exciting,

because New Horizons had
just flown past Pluto.

So what have been the most
exciting findings so far?

So, I think there's two
that really jumped out for me.

One is actually to do with Charon.

So, Charon, of course,
is Pluto's biggest moon.

It's most of the same size as Pluto,

it's very large indeed,
compared to its orbital parent body,

and so we didn't know
it had a red pole.

And so there was a lot of work
that's gone into

trying to understand
what's going on.

And now, after two years
of analysis,

Carly's team think
they finally have an answer.

Charon is stealing
Pluto's atmosphere,

which is freezing at its poles,
then turning slowly red.

So, we think that Charon's poles are
red because they're sort of nabbing

some of Pluto's atmosphere
as it's being lost,

which I think is phenomenal.

But this process happens
incredibly slowly.

So, Pluto has
a very thin atmosphere,

and so you end up with
about 1.5 millimetres

per million Earth years. Whoa!

So this process is not something
that's happening overnight,

this is a very, very slow process,
and it tells you, really,

that Charon's surface must be
incredibly stable.

There's not an overturning,
there's not a change in the surface,

because otherwise that reddening
couldn't have happened.

But there's also talk
that Pluto has a heat source.

Has that been confirmed?

The origins of that is
that there's these shapes

that have very discrete boundaries,

and what we think is,
they're like lava lamps,

so they're getting heated
from the bottom,

slowly the material is rising up,
and then falling back down again.

Now, there's two ideas,

one is that the energy source
from that is from the interior

and it's leftover radioactive decay.

If it's radioactivity,
wouldn't it have decayed long ago?

So, we think that, actually,
there's enough remnant radiation,

because you just don't need enough,
you just need a little bit.

We're still trying to figure out
whether it's just purely sunlight,

whether sunlight's enough to drive
it, or whether we do need

to sort of invoke extra radiation,
um...sort of a superpower

for Pluto, for radiation to allow
this convection to happen.

But we certainly don't need
a lot of heat for it to happen,

a few degrees is all that's needed.

We've got all these
fantastic results,

but what's next for New Horizons?

New Horizons is still busy, we found
another target for it to visit.

It's got a very catchy name
of 2014 MU69,

and this is a very small object

that's located in the Kuiper Belt.

We think it's never been heated up,
so again, it's this sort of remnant

of the early Solar System.

Which is, again, important
in order to understand

our own Solar System
formation theory.

It hasn't been modified since

basically the dawn of our Solar
System, so it's very exciting.

So, we're observing
things en route,

but our next target we reach
on the 1st of January in 2019.

So, there's going to be quite a lot
of scientists that are going to be

very sober on New Year's Eve 2018.
THEY LAUGH

So, Carly, what have we learned
from its journey?

Oh, we've learned so many things.

I think we've learned that
this region of space is not boring,

it's not dead.
Activity is happening,

there's variation
across different targets.

This is a region of space
that really wasn't known

very much at all,
and it's completely revolutionised

our understanding of these targets.

Well, Carly, thank you
for talking to us again,

and we look forward to getting the
latest results as they come through.

Thanks for your time.

Most of the Trans-Neptunian Objects

are leftovers from the origins
of the Solar System.

This means they contain important
clues as to how it evolved.

Scientists believe they've played
a significant part

in the Solar System's
most turbulent period,

a time when the orbits of
the planets changed dramatically,

and they suggest there's a chance
that this might happen again.

To understand how
such relatively small objects

play such an important role,

you need a very particular tool...

mathematics.

Marcus du Sautoy explains.

For a mathematician like me,
what's so fascinating

is that the planets,
the Moon, the stars, all move

through the night sky following
very strict mathematical rules.

And this idea is perfectly captured
by this thing here.

It's called an orrery.

An orrery is a model of the planets
revolving around the sun

that runs on one of the most
beautiful mathematical systems,

clockwork.

Mathematics describes the clockwork
nature of the way the planets move

around the Sun
with such remarkable detail

that we're able to make predictions
about where the planets will be

into the future
with pinpoint accuracy.

This is because of
Newton's theory of gravity -

a mathematical equation that shows
how objects attract each other

through gravitational force.

Crucially, this means that as
the planets and other objects move,

they can influence each other
in ways that can be very profound.

Let's suppose this metal ball
is a planet orbiting the Sun.

Let's set it off on its orbit.

I'm going to use this magnet

to represent the influence
of a second planet.

So I should be able to give a kick

to the stable orbit
of this first planet.

There, see, we're starting
to influence the orbit

of the first planet
in quite a dramatic way.

When one object or planet
affects another via gravity,

we call it perturbation,

and it's an influence which has had
a major effect on the Solar System.

And over the years, we've used
the mathematics of perturbation

to solve some of the great mysteries
of the Solar System.

For instance, in the 19th century,

the predictions of the position of
Uranus were discovered to be wrong.

And mathematicians guessed
this could actually be due

to another planet
perturbing the orbit of Uranus.

And within 20 years, they found it.

It was named after
the Roman god of the sea,

Neptune.

Mathematics doesn't just help us

to predict where objects will be
in the future,

it also helps us to understand the
very structure of the Solar System,

how it evolved
and how it might eventually end.

And many believe that
the Trans-Neptunian Objects

are evidence of this mathematics
at work,

because of my second
mathematical principle -

resonance.

This is a Barton pendulum,

and it shows how,
under certain circumstances,

a regular pattern can
powerfully influence another

through something called resonance.

I've got a series of pendulums
hanging from a string here,

and I've got a driver pendulum.

And when I set this off,

the energy is going to get
transferred to the other pendulums,

but they're not all going
to react in the same way.

LANGUID PIANO MUSIC PLAYS

What we see is that these two
pendulums are swinging much more

than the others, and this is
because they're in resonance.

Resonance occurs when a pendulum
absorbs the momentum easily

from the driver
and relates to its length.

And some lengths
work better than others.

So, here, the length of the string
is the same as the driver,

and this one is in a 2:3 ratio.

Amazingly, the same thing can happen
with the planets and the moons.

The gravitational attraction
as they orbit means that,

under certain circumstances,
they can begin to resonate.

So they kind of get locked in,
creating a regular pattern.

For instance,
Pluto resonates with Neptune,

orbiting twice
for Neptune's three times.

And the Trans-Neptunian Objects
resonate too.

Although this resonance seems
to create order and balance,

it's not guaranteed, because,
as with any finely balanced object,

it's easy for it
to become destabilised.

Which brings us on
to another mathematical subject

called chaos theory.

Roughly speaking, the idea reveals
how a small change in the present

can have dramatic implications
for the future.

Consider this pendulum here.

If I set it off, then it does
exactly what you'd expect it to do.

If I now add a magnet to the base,
then it perturbs the orbit.

It's still pretty predictable,
but it's beginning to wobble.

But now, if I add
two more magnets to the base,

the orbit becomes
wildly unpredictable.

More accurately,
what mathematicians mean by chaos

is that a small change
in the starting position

can cause a completely different
outcome

for the trajectory of the pendulum.

What we've come to realise
in the last few years

is that our Solar System has
much more in common

with this chaotic pendulum
than we ever imagined.

Far from being
stable and predictable,

it's actually unstable and chaotic.

And a small wobble of a tiny object
could theoretically change

the whole structure
of the Solar System completely.

But how about this for a thought?

Scientists now believe that chaotic
disturbances have already played

a critical role in the history
of our Solar System.

In particular, they suggest
there may have been

a chaotic resonance catastrophe
around 4.5 billion years ago.

As well as messing with the planets,

this might also finally explain

the weird orbits, spins
and positions

of the Trans-Neptunian Objects.

To find out more,

Chris met up with Marek Kukula
of Greenwich Observatory.

So what's the story?

What did happen
4.5, 5 billion years ago?

Well, the most popular model
for what might have happened is

called the Nice model.

It's named after
the Observatoire de la Cote d'Azur,

down in Nice in France, where
the model was first come up with,

in 2005, I think.

And the idea here is
that the giant planets -

Jupiter, Saturn, Uranus
and Neptune -

were all in very neat orbits, but
closer to the Sun than they are now,

and beyond them was
this very thick, dense Kuiper Belt,

very different to the one
that we have today.

So, although it looked,

perhaps from the outside,
very neat and stable,

actually the seeds of its own
destruction were already there.

And what happens is that the giant
planets are able to pull in

the smaller objects from the Kuiper
Belt and they flick them inwards.

But when the small objects start
to get into the realm of Jupiter,

then something
a little bit different happens.

Jupiter, obviously,
the most massive planet,

its gravity is very powerful.

It's able, actually,
to flick these objects

not further in, but further out,

it's flicking them perhaps even
out of the Solar System entirely.

And of course,
if it's flicking them out,

it has to move further in.

So, Saturn, the other giant planets
are moving out,

Jupiter is moving in, and then you
get to the situation where we have

a resonance, where Jupiter is going
around the sun twice

for every one orbit
that Saturn makes.

That resonance is
a very powerful situation,

and that means that,
as they do that,

they're giving very regular
gravitational tugs

to Uranus, to Neptune
and to the Kuiper Belt objects.

So what you get is,

as Jupiter and Saturn are doing
this resonance thing,

they are pushing Uranus and Neptune
further out

and they've pushed them out
into this dense Kuiper Belt.

That's very chaotic.

These smaller objects are being
thrown in all directions.

Many of them are being flung
into the Solar System,

and this is where
all hell breaks loose.

This computer simulation shows
this moment of resonance,

followed by chaos.

The Kuiper Belt is in green and
the outer planets are in the centre.

Suddenly, Jupiter and Saturn
wreak havoc,

and the Kuiper Belt is scattered.

When that process is finished,

Uranus and Neptune
perhaps swap places.

They and Saturn have moved
further out from the Sun,

the Kuiper Belt has been scattered
in all directions.

It's now much less dense
and much more extensive,

and this is why we have
the Solar System that we have today.

So, when we think about the chaos

that still exists
in the Solar System,

the potential for chaos,
the fact that things could change,

what's the worst that could happen?

Should we be worried?

Well, perhaps a little bit worried.

If you look at the Solar System
as it is today,

it does look fairly stable,
but in fact that's an illusion.

And if you look at all of the orbits
of the planets, the other objects,

the Kuiper Belt, the asteroids,
it is still rather a chaotic system.

It turns out that Mercury's orbit is
not particularly stable

and there is a small,
perhaps 1% chance,

that over the next few tens
or hundreds of millions of years,

Jupiter's influence on Mercury
could cause it

either to crash into the Sun,

to fly out of the Solar System
entirely,

or perhaps even to crash
into either Venus or the Earth.

So, no sign that that's happening,
but we can't be certain.

We can't rule it out.

It's a small possibility, but it
is a real, finite possibility,

so we're still living in chaotic
times, the chaos isn't over yet.

It seems now that the exploration

of the weird world
of Trans-Neptunian Objects

is presenting us with a new
chaotic picture of our Solar System.

This is light years away
from the stable, predictable one

we thought we knew before.

And there's still
so much more to explore.

I'm so impressed by what's being
found in the outer Solar System -

the diversity of worlds,
but also their sheer number.

800 new places
in that one survey alone,

and who knows
what else is out there?

But that's the exciting thing,
I think.

We're discovering new things
all the time,

and by looking at these objects
so far away from the Sun,

we're discovering about
the evolution

of the whole of the Solar System.

That's all we have time for
in this programme,

but do join us next month

when we'll be looking at
the profound effect

that space has here on Earth,

from a deluge of space dust
to the beauty of a meteor storm,

to the potential for life itself.

And in the meantime, do check out
our website at bbc.co.uk/skyatnight,

where you'll find exclusive content,
including a star guide.

In the meantime, of course,
get outside and...

get looking up.

Goodnight.