Review of the Year The Sky at Night

-Thank you.

-2016 will be remembered for many different reasons.

Brexit means Brexit...

But whatever you thought of the events of this year,

one thing is certain -

it has been one of the most extraordinary years

in space exploration.

Scientists are hailing a major discovery...

We have detected...

gravitational waves. We did it.

CHEERING AND APPLAUSE

We have a spacecraft in orbit around Jupiter,

and I think people are rather pleased.

I don't think I can remember a year

which has delivered so much in terms of discovery and exploration,

and we've been lucky enough

to have a ringside seat for many of this year's remarkable events.

But the things that we report on are usually

just the beginning of the story.

The most exciting developments happen in the weeks

and months that follow, as the serious science cuts in.

And so tonight, we're bringing you bang up-to-date with many

of the biggest stories of 2016.

Welcome to The Sky At Night.

There were four huge stories in 2016 and they've all seen

significant new developments since we encountered them.

Tonight we'll be looking back at these stories and revealing

what's happened since we first reported on them.

We'll be finding out more about Planet Nine, the mysterious planet

that may orbit in the very outer reaches of the solar system.

We'll be investigating what the recent discovery

of gravitational waves can tell us about the rest of the universe.

And we'll be asking whether we're any closer to understanding

Proxima B, the newly-discovered and potentially earthlike planet

orbiting our nearest neighbouring star.

And if Father Christmas brings you a new telescope,

then we have good news - Peter's here with a quick guide

to show you how to get the best from it.

But first we return

to the biggest, most exciting mission of the year,

one that would go where no spacecraft has gone before.

Back in July, I travelled to NASA's Jet Propulsion Laboratory to witness

the arrival of the Juno probe as it entered orbit around Jupiter.

It was to be the first craft to slip through Jupiter's vast

and intense radiation belts,

flying just 5,000km above the gas giant's cloud tops.

No-one knew if it would survive its entry into Jovian orbit.

CHEERING AND APPLAUSE

There it is! Juno right on time, into orbit, exactly as planned.

After five years in space, Juno had made it into orbit

within 1.2 seconds of the schedule, and the team was delighted.

-Ooh!

-Congratulations.

-Yay!

-So it went well, then?

-It went great!

Just, I mean, what were they,

-like one second off, or something ridiculous?

-Perfect.

It's perfect, so now we've got... The work is going to start.

We get the data, we've got to do the work.

In the five months since then,

that work has started to deliver amazing results.

Maggie met up with planetary scientist Leigh Fletcher

to find out how the data that Juno has already returned

are transforming our understanding of the giant planet.

Leigh, thanks so much for coming in.

Now, Juno's gone into orbit about Jupiter,

but it's had a few challenges.

Yes, when we first got into Jovian orbit back in July of 2016

we went into a 53-day orbit. The idea was

we were looping high over the North Pole, then coming in very,

very close to the planet and going back out over the South Pole.

Now, the plan all along had been to fire the engines in October

of this year to move us from that 53-day orbit

into a two-week orbit.

Now, just before they were due to do that firing of the engine,

they discovered that there was an issue with one of the valves,

these are part of the propulsion system,

they simply weren't opening and closing quite as quickly

as they intended, so rather than take any risks,

the programme managers decided that they were going to postpone

that burn, and at the moment, we're staying in that 53-day orbit.

Now to me, if you're in a 53-day orbit rather than

a two-week orbit, that seems like less data.

It's actually not a massive amount of difference.

We'll get exactly the same science

and we'll be covering exactly the same regions of the planet.

It will just take longer,

so we're having to learn to be slightly more patient.

So, what did you see from that first encounter?

Well, one of the wonderful things about Juno's orbit

is it's giving us a vantage point we have never,

ever had before, the ability to look at the poles of Jupiter.

What I'm going to show you now is one of those first-ever

images of the South Pole of Jupiter.

So you're seeing light being reflected from the day side

just here, and the night side down here,

and as we zoom into this image, you can see the incredible

structures that we're seeing here at the South Pole.

These are pinwheel storms that are presumably moving

and migrating all over the South Pole itself, so this is the

South Pole of Jupiter, but of course we saw the North Pole as well.

Here it is, again in this incredible detail.

If we just zoom in again, you see all of these pinwheel storms

and cyclones that are taking place, no belt zone structure,

but the thing I'm most excited about is what's going on up here.

What you have is a cloud that's actually rising up from the night

side of Jupiter and it's getting so high in the planet's atmosphere

that it's catching the dying rays of the sun as the sun is going down.

As well as the camera, that operates in visible light,

Juno is equipped with a whole suite of instruments

to probe the planet in other ways...

..including its infrared imager

that can penetrate Jupiter's cloud tops

and reveal the vast scale of its aurorae.

When we first saw this image, it really knocked our socks off.

I'm not surprised.

What you're looking at is the aurora at the South Pole of Jupiter,

glowing because hydrogen ions are emitting their light

as they're being bombarded by these electrons.

It looks like a wall of fire, many times the size of the Earth.

All of this incredible structure will be changing,

ebbing and flowing over the course of just a few minutes.

Amazing stuff.

Now what I can show you next are the very first observations from

the microwave instrument on board Juno that's allowing us

to see down below the clouds.

Now, this image on the right-hand side is what you're familiar with,

it's the banded structure of Jupiter.

We've got the red spot there, all of this looks very familiar.

Absolutely, so this is light being reflected

from the topmost cloud deck.

These slices that you see on the left are probing deeper

and deeper and deeper down into the interior depths.

If you look at these,

it's obvious that we are actually seeing banded structures still

down in the interior of Jupiter, down 300km below these cloud decks.

So what this means is that the surface that we're seeing

is just the tip of the iceberg and that below that tip we're seeing

an enormous circulation or atmospheric pattern that will

keep atmospheric scientists going for years, trying to interpret

what is actually taking place.

Please come back again and tell us more about this amazing planet.

-Will do, thank you.

-Thank you very much.

And that brings us to our second highlight of the year.

At the end of August, just days before Juno's first close pass

around Jupiter, news came of another tremendously exciting announcement.

Now scientists are hailing a major discovery,

a new planet which they've called Proxima B.

At just four light years away, it's relatively close to us.

It's roughly the same size as Earth,

and because it's just the right distance away from its star,

it could be the right temperature to have liquid water and possibly life.

The planet was found orbiting Proxima Centauri,

our closest neighbouring star.

At just over four light years away, it's just close enough

to imagine that we might one day be able to send a spacecraft there.

Having a planet around Proxima is exciting and pretty much

everyone who studies exoplanets has scrambled to have their say

about what it must really be like.

In some ways, the planet is very different from the Earth.

It orbits just 7.5 million kilometres from its star -

that's roughly 20 times closer than the Earth is to the sun.

But because Proxima Centauri is so much cooler and dimmer

than our sun, the planet could be a similar temperature to the Earth.

But being so close to its star could also create other problems.

For example, it was thought that Proxima was a violent star,

sending stellar flares towards the planet,

and making it an inhospitable place.

But new research seems to show that it's no more violent than our sun.

But there remain many unknowns.

We've no real idea what the planet is like.

We can't observe it directly and so everything we know

we've had to infer by watching the gravitational effect

that it has on its star.

And so a French team have tried to work out the planet's

characteristics by using comparisons with the planets

in our own solar system.

If it has a large metallic core and a rocky mantle,

like Mercury does,

then it's probably a little bit smaller than the Earth,

but there are other, more exotic possibilities.

It could be much bigger than the Earth, 1.4 times the size,

in which case it would have to have a rocky core, surrounded by

a mantle of ice, and excitingly, the model suggests that

the entire planet would then be covered in a vast ocean, 200km deep.

All this speculation is great fun,

but what we really need are more observations.

But those observations will be extremely challenging.

The planet is too small and too faint to be directly imaged

with current telescopes.

And so we must wait for the next generation of instruments

before we can understand its true nature.

The story of Proxima B has a long way to run.

Earlier this year we asked for your help to identify

a new class of comet hidden in the asteroid belt.

These main belt comets are similar to ordinary asteroids,

apart from they occasionally sprout tails.

Very little is known about these strange objects,

but their tails are almost certainly produced by pockets of ice,

vaporising as they are heated by the sun.

That means that these main belt comets could represent

a huge and previously unknown source of water in the inner solar system.

But only a handful have been found,

so we sent out a call to get you searching for them.

We had a fantastic response and Sky At Night viewers have

contributed to identifying over 340,000 images to date.

And from them, you identified these two, which appear to be

producing tails and which could be newly-discovered comets.

The next step is to observe these objects

through the 8.2-metre Subaru telescope in Hawaii.

This will hopefully occur early next year and it will help

the team to identify whether these really are main belt comets,

and we'll bring you the results as soon as we have them.

The Comet Hunters project shows the power and the potential

of everyone to make new discoveries.

If you're inspired to become a stargazer yourself,

or if you're getting a telescope for Christmas, Pete is here

with some tips on how to get the best results.

Now, it's probably fair to say

that astronomy isn't the cheapest of hobbies,

but for a few hundred pounds you can get some pretty decent kit

and there are plenty of manufacturers out there that

make packages such as this.

Now, here I've got a very sturdy tripod at the bottom

to hold everything very steady.

On top of that, I've got an equatorial mount head,

and this one has a motor attached to it.

Now this has the job of counteracting the Earth's rotation,

so it keeps everything that I'm looking at through the eyepiece

in exactly the same position.

On top of that, I've got my telescope tube,

and in this case, this is a 70mm refracting telescope.

This is an ideal size to view the moon and deep sky objects,

such as open clusters and galaxies.

To align the telescope properly,

it needs to be balanced on the mount.

And the mount needs to be pointed as accurately as possible

at the celestial pole, which is close to the North Star.

Once you've got your telescope set up, you need to leave it

for about an hour to cool down to the outside temperature.

That will also allow your eyes to adapt to the darkness.

And then you are ready to start observing.

And what I'm going to line up on tonight is the Andromeda Galaxy,

Messier 31.

That's our nearest, largest neighbouring galaxy.

The Andromeda Galaxy is located almost overhead

during early evening

to the north-east of

the Great Square of Pegasus.

Use the right-hand side of the W-shape constellation of

Cassiopeia as a pointer to it.

Point your scope at the galaxy,

lining its elliptical haze up with the finder's crosshairs.

If you want to take pictures of what you're observing,

you can add an adapter ring that will connect most DSLR cameras

to the telescope.

But bear in mind that you'll have to rebalance the scope

to take into account the weight of the camera.

So, trying the ISO setting of between 400 and 1,600,

the higher you go, the noisier the end result will be.

Also an inexpensive shutter release cable like this is a great idea,

because it allows you to take your pictures without

touching the camera and wobbling the telescope.

Now, for a tracking mount like this, exposures between,

say, 30 and 120 seconds are possible.

The key to success is to experiment.

There it is, the Andromeda Galaxy, and beautiful it looks too.

Look at that, there's so much detail in there.

I've got the core, I've got the spiral arms which are really

faint, sort of, going round the core,

and I can see the dark dust lanes running through the galaxy as well.

And I've got the satellite galaxies, M32 and M110, also in that shot.

Loads of detail. And with a fairly basic set-up. It's amazing.

Our third highlight of the year was announced way back in January.

And it took both the scientific community and the public by surprise.

A team of researchers from Caltech claimed that they had

evidence for a ninth planet.

Hidden in the outer reaches of our solar system,

far beyond the icy realm of the Kuiper Belt.

I set out to demonstrate just how extreme this planet's orbit was.

On this scale, every centimetre is about 35 million kilometres.

The Earth is 150 million kilometres from the sun.

Pluto is 40 times further away

and the outer edge of the Kuiper Belt is still further.

But Planet Nine is far beyond that.

At the point of closest approach in its orbit,

it sits 200 times further from the sun than the Earth.

That's a whopping 30 billion kilometres away from the sun.

But unlike the other planets,

the proposed orbit of Planet Nine is not circular.

Its highly eccentric path takes it much, much deeper into space.

At its furthest possible point, its aphelion,

it could be as much as 1,200 times further from the sun than the Earth.

On this scale it's 54 metres away.

In reality it would be 180 billion kilometres from the sun.

This discovery was enormous news,

but there was one crucial stumbling block.

No-one had actually seen Planet Nine.

Its existence had only been predicted by computer models

that had been built by Caltech astronomers Mike Brown and Constantine Batygin.

They'd been trying to understand the unusual elliptical orbits of

six distant objects out in the Kuiper Belt, seen here in pink.

They found that the only way they could replicate these orbits

was if there was a ninth planet orbiting far beyond Neptune.

When I met Mike shortly after the announcement in January,

he explained to me that the next challenge would be to find the planet.

Clear sky, sort of. Where is it? Where's this planet?

Well, we know its path across the sky.

We know its orbit, so we know the path and the path across the sky goes from somewhere over here,

up across here right through the middle of Orion and Taurus and then down south across this way,

and then of course all the way back around.

We actually also know that around Orion and Taurus is where it's

the most distant from the sun.

And we think that's where it is.

We think that the places that are closer to the sun, it would be too bright, we would have seen it.

I mean, we're not talking amateur telescopes here to find this.

No, in the end it's going to take us some time on the biggest

telescopes in the world, but with the biggest telescopes in the world,

it is well within range and we'll be able to find it.

-It's up there somewhere, probably.

-Right there.

Many astronomers are yet to be convinced, and so I recently

caught up with Mike again to see how the search was going.

-Hello?

-Hey, Mike, it's Chris. How are you?

-Good, Chris, how are you?

-Yeah, nice to see you.

So, look, I'm not going to waste any time.

Have you found Planet Nine yet?

-No.

-Excellent, thank you! THEY LAUGH

What progress do you have to report?

My favourite one that we realised just this last summer is

something that has been known since 1850 and has had

no explanation, which is if you look at the planets of our solar system,

all eight planets, they're in a disc.

And that disc, the inclinations,

the amount that they're tilted relative to each other,

is less than one degree on average,

so all eight planets are within this one little one-degree disc.

The sun is tilted from that disc by about six degrees.

It's really a strange thing.

No-one has had a very good explanation for 160 years.

And in fact it's been so unexplainable that most people don't even realise that it's true.

So, we quickly sat down and did this calculation to figure it out

and realised that our prediction of Planet Nine, and of where Planet

Nine is, predicts about a six-degree tilt just like the tilt that we see

and the exact direction that the sun is actually tilted.

It was one of those remarkable moments where you do this

calculation not knowing what the answer's going to be,

and it comes out exactly what you were hoping it was going to be.

So, lots of people are looking. Have you had sceptical reaction as well?

Clearly not everyone's as sure as you are.

What have the negative reactions been?

Are people still questioning whether this is just chance, these alignments?

Yeah, so, scientists as a rule are a sceptical tribe,

and if you're going to be sceptical of anything,

you should be sceptical of somebody claiming there's a planet out in the outer solar system,

because people have been claiming this for

approximately the last 165 years, and every time it's been a mistake.

So, there are people trying very hard to show that it's not true.

So far I haven't seen anything that has been convincingly showing

that it's not really out there.

Well, just before we let you go to get back to trying to find this

thing for us, I'm going to make you bet, I think - next year, 2017?

At the beginning of this year, I was cautious and I said five years.

And now, I tell you, we have narrowed down the search area

to such a small area with these calculations.

I'm going to guess that next year...

Next year's the year.

I'm... I feel optimistic.

OK, well, we'll talk to you then. Good luck.

-All right, thank you very much.

-Thanks, Mike.

Mike certainly sounds convinced,

even more than he did at the start of the year,

and the evidence does seem to be piling up,

so let's hope he's right and 2017 is the year that we find Planet Nine.

Our fourth and final story comes from much, much deeper in space.

Back in January, Planet Nine was described as potentially the discovery of the century.

But then, just three weeks later, scientists at the Advanced

LIGO instrument in the States made an even bigger announcement.

-BBC NEWS HEADLINES:

-Unravelling the secrets of the universe -

the most important scientific discovery for a generation.

Scientists in the United States have announced they have

discovered gravitational waves.

Einstein was right after all.

Gravitational waves ripple through space and time.

Gravitational waves were a key feature of Einstein's theory

of general relativity.

And the fact that they were discovered exactly a century after

he predicted them strengthens his theory.

But gravitational waves gives us so much more,

cos they allow us to see some of the most exotic bodies in the universe,

because what LIGO had detected was the collision

between two black holes.

Black holes are difficult to study by conventional means,

because they do not emit any light.

But the LIGO measurements suddenly gave us

a way to observe exactly what happens when black holes collide.

1.3 billion light years away the two black holes,

36 and 29 times the mass of the sun,

have been orbiting each other in a binary system, before colliding

with such force that they sent tremors rippling through space-time.

But by the time they reached Earth,

the waves had dissipated so much they caused a disturbance in

LIGO's detectors that was only 1/1000th the width of a proton.

A lot has happened since we brought you that first detection.

In fact, just three months later,

another collision between black holes was detected and then

a third, but the signal for that one was

a bit too weak to get full confirmation.

But this collection of collisions gives us an indication that

these events which we thought were rare may be relatively common.

And these new discoveries are also causing us to reassess our ideas

about the nature and formation of black holes.

The data had revealed that some black holes spin at enormous

speeds, 10% of the speed of light, much faster than we expected.

And then there's a problem that the black holes detected in

the first collision are far too massive to exist in a binary system.

Black holes form from the collapse of massive stars at the end

of their lifetimes.

It had always been assumed that black hole pairs formed

from binary star systems.

But the black holes in the LIGO observations are so vast, they

must have formed from stars that were too big to survive as binaries.

They would have fallen into each other and merged long before

they could have formed black holes.

So, we need a new model to understand how black holes collide.

It may be that instead of forming in a binary star system

that the two black holes formed independently,

maybe in a dense star cluster, then gravitated towards each other,

forming a binary pair which then collapsed.

What's really exciting about this gravitational wave discovery

is that it lets us see things that were previously hidden.

Instead of relying on light in looking only at things that shine,

we have a whole new way to observe the universe.

LIGO has just begun its second run, and detections are expected

to come thick and fast over the coming months and years.

We don't know what these next observations will reveal,

but we do know that when people look back at this first discovery

in 2016, they'll see it as a great moment in the history of

astronomy, as transformative as the invention of the radio telescope.

That brings us to the end of the four major stories we covered this year.

But there have been many other exciting events

that slipped by without fanfare.

Two. One...

In September we saw the launch of Osiris Rex, an ambitious

new mission to collect a sample of an asteroid and return it to Earth.

Elsewhere in the solar system,

it's been a good year for discovering water.

An ice volcano twice the size of Everest was found

on the dwarf planet Ceres.

Plumes of water had been detected erupting from Jupiter's moon Europa.

And there's fresh evidence for the existence of

a subsurface ocean on Pluto.

Further afield, astronomers have discovered that there are ten times

more galaxies in the observable universe than first thought.

Some two trillion of them.

One of them, Dragonfly 44,

has been found to be made of 99.9% dark matter.

Making it the largest dark matter galaxy ever observed.

2016 is coming to an end,

but there's lots of exciting stuff for the New Year.

Yes, we've got the launch of not one but two exoplanet missions,

a total solar eclipse in the US,

more from LIGO and I'm looking forward to Curiosity climbing

the slopes of Mount Sharp, but what are you most excited about?

Well, for me it is all about the end of Cassini. It's been an epic

mission and now it's coming to an end, and it's going to be

a grand finale as the spacecraft plunges into the depths of Saturn.

-What a way to go.

-Yeah, it's a shame it's got to end, but it will be spectacular.

That's it from us from this year, but we'll be back in January,

so you don't have long to wait.

And in the meantime, don't forget to go to the website to check out

this month's guide to the night sky.

And, as usual, get outside and get looking up.

Goodnight.