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This remarkable object is one of the oldest surviving images of the | 0:00:04 | 0:00:07 | |
night sky, showing the moon in 1857, | 0:00:07 | 0:00:11 | |
not long after the process of photography had been invented. | 0:00:11 | 0:00:15 | |
It's a beautiful, fragile and wonderful thing. | 0:00:15 | 0:00:18 | |
But what it represented at the time was a spectacular | 0:00:18 | 0:00:21 | |
breakthrough in technology. | 0:00:21 | 0:00:23 | |
Since then, we've come a long way. | 0:00:23 | 0:00:26 | |
For the past 50 years, | 0:00:26 | 0:00:28 | |
we've been sending spacecraft around the solar system. | 0:00:28 | 0:00:32 | |
And they have been sending back the most amazing pictures. | 0:00:32 | 0:00:36 | |
On tonight's programme, we'll be revealing our choice | 0:00:36 | 0:00:40 | |
of the five most stunning images ever taken of the solar system. | 0:00:40 | 0:00:44 | |
We'll be investigating why these images were taken | 0:00:44 | 0:00:47 | |
and how they've transformed our understanding of these alien worlds. | 0:00:47 | 0:00:51 | |
Welcome to The Sky At Night. | 0:00:51 | 0:00:53 | |
Appropriately enough, | 0:01:25 | 0:01:28 | |
we're at the Natural History Museum's Other Worlds exhibition. | 0:01:28 | 0:01:31 | |
A collection of spectacular images of the solar system. | 0:01:31 | 0:01:34 | |
What's stunning about capturing images like these, | 0:01:37 | 0:01:40 | |
of other bodies within our solar system, is that it would have been | 0:01:40 | 0:01:43 | |
inconceivable just one generation ago. | 0:01:43 | 0:01:46 | |
Over the next half hour, we're going to bring you remarkable | 0:01:46 | 0:01:48 | |
and striking images from all over the solar system. | 0:01:48 | 0:01:51 | |
And we've chosen what we think are the five most significant, | 0:01:51 | 0:01:55 | |
based on three criteria. | 0:01:55 | 0:01:56 | |
Firstly, scientific interest. | 0:01:56 | 0:01:59 | |
Each image needs to reveal something about our solar system, | 0:01:59 | 0:02:02 | |
how it works or its history. | 0:02:02 | 0:02:04 | |
And secondly, they need to represent a technological advance, | 0:02:04 | 0:02:07 | |
a new way of seeing the solar system. | 0:02:07 | 0:02:09 | |
And finally, of course, | 0:02:09 | 0:02:11 | |
each image needs to be absolutely visually stunning. | 0:02:11 | 0:02:15 | |
There are literally thousands of images we could have chosen. | 0:02:15 | 0:02:20 | |
But we've settled on what we think are the top five. | 0:02:20 | 0:02:24 | |
We start by considering images of Saturn. | 0:02:25 | 0:02:28 | |
Saturn has always been considered to be the most beautiful planet | 0:02:31 | 0:02:35 | |
and since 2004, the Cassini space probe has been in orbit about it | 0:02:35 | 0:02:39 | |
and it has sent back some extraordinary pictures. | 0:02:39 | 0:02:43 | |
And our choice for the iconic picture of the Saturn system is this | 0:02:45 | 0:02:50 | |
breathtaking portrait of the planet and its rings. | 0:02:50 | 0:02:55 | |
To explain the intricacies of this stunning image, | 0:03:02 | 0:03:05 | |
I've been joined by Cassini imaging team's scientist Carl Murray. | 0:03:05 | 0:03:10 | |
Carl, this is an extraordinary image of the planet Saturn and its rings. | 0:03:10 | 0:03:14 | |
But there is so much here, can you guide me through? | 0:03:14 | 0:03:17 | |
Well, it's actually 141 different images all mosaicked together. | 0:03:17 | 0:03:21 | |
But taken in a very special geometry, | 0:03:21 | 0:03:23 | |
when the sun was eclipsed by Saturn. | 0:03:23 | 0:03:26 | |
So, we are in the shadow of Saturn, | 0:03:26 | 0:03:28 | |
the spacecraft is in the shadow of Saturn when the image was taken. | 0:03:28 | 0:03:32 | |
So, what we see is a kind of a unique view. | 0:03:32 | 0:03:34 | |
We can see, for example, this bright ring around the planet, | 0:03:34 | 0:03:38 | |
which is the sunlight being refracted through the atmosphere. | 0:03:38 | 0:03:41 | |
We can see the main rings themselves | 0:03:41 | 0:03:43 | |
and we start to see these other rings, | 0:03:43 | 0:03:45 | |
which are normally almost invisible to see. | 0:03:45 | 0:03:49 | |
But this geometry, this alignment with the sun allows us to see | 0:03:49 | 0:03:52 | |
these faint rings and learn something about them. | 0:03:52 | 0:03:56 | |
Yes, they seem to be so far out beyond the planet. | 0:03:56 | 0:03:59 | |
-It's just a huge system. -It is. In fact, | 0:03:59 | 0:04:02 | |
this whole image is covering about 600,000 kilometres across. | 0:04:02 | 0:04:06 | |
So, there's the planet, which is | 0:04:06 | 0:04:09 | |
about 60,000 kilometres across and then this vast, | 0:04:09 | 0:04:12 | |
main ring system here | 0:04:12 | 0:04:13 | |
and then these faint rings going out beyond that. | 0:04:13 | 0:04:16 | |
There's all sorts of colours going on here. Now, is this real data? | 0:04:16 | 0:04:20 | |
-Or is it an artificial colour? -The differences are real. | 0:04:20 | 0:04:24 | |
So, for example, the main rings you see, | 0:04:24 | 0:04:26 | |
we know are composed of water ice. We've known that for some time. | 0:04:26 | 0:04:30 | |
So, you would expect that to be essentially white, | 0:04:30 | 0:04:32 | |
but there are some contaminants in the rings as well. | 0:04:32 | 0:04:35 | |
So, there's a slight reddishness to the rings, which, | 0:04:35 | 0:04:38 | |
combined with the water ice gives this sort of yellowish colour. | 0:04:38 | 0:04:41 | |
But the photo reveals more than just the rings. | 0:04:41 | 0:04:44 | |
Elsewhere in the image, we see several of Saturn's 62 moons. | 0:04:44 | 0:04:48 | |
And the photograph also reveals how the formation of Saturn's | 0:04:51 | 0:04:55 | |
rings and moons are entwined. | 0:04:55 | 0:04:56 | |
This is the moon Enceladus. | 0:04:58 | 0:05:00 | |
So, this is active. We think there's liquid water, | 0:05:00 | 0:05:04 | |
possibly even a global ocean of liquid water underneath. | 0:05:04 | 0:05:06 | |
And this material is coming | 0:05:06 | 0:05:08 | |
out at pressure and going out to several hundred kilometres. | 0:05:08 | 0:05:11 | |
And then just, sort of, wandering around. | 0:05:11 | 0:05:14 | |
If you just look really closely, you can actually see | 0:05:14 | 0:05:17 | |
-plumes of material coming out of the south polar region. -Yes. | 0:05:17 | 0:05:20 | |
And that has created the entire E ring. | 0:05:20 | 0:05:22 | |
-So, it shows this connection between rings and moons. -Yeah. | 0:05:22 | 0:05:25 | |
And it seems to be quite a strong one. | 0:05:25 | 0:05:28 | |
So, moons forming rings and then, sometimes, rings forming moons? | 0:05:28 | 0:05:32 | |
-Yes. -I find that surprising. | 0:05:32 | 0:05:34 | |
I did too, when it was first proposed, | 0:05:34 | 0:05:36 | |
but we know that material naturally can accrete in the rings. | 0:05:36 | 0:05:39 | |
Supposing you get a large enough mass, then it could start | 0:05:39 | 0:05:43 | |
evolving, as it interacts with the ring material around it. | 0:05:43 | 0:05:46 | |
And, maybe, even escape from the rings and then move outwards. | 0:05:46 | 0:05:50 | |
And maybe catch up with another one that had ready escaped | 0:05:50 | 0:05:53 | |
and get larger. And they originally proposed it for small moons | 0:05:53 | 0:05:56 | |
and they think now maybe even the larger moons of Saturn | 0:05:56 | 0:06:00 | |
and indeed other giant planets could have formed in this way. | 0:06:00 | 0:06:03 | |
So, rings can lead to moons. If moons break up, they can lead | 0:06:03 | 0:06:08 | |
to rings. And it's a very interesting process that goes on. | 0:06:08 | 0:06:11 | |
-Yeah, far more dynamic than I ever realised. -Exactly. | 0:06:11 | 0:06:14 | |
Now, you have this, what I like to call | 0:06:14 | 0:06:17 | |
an accretion disc, with a large mass in the centre. | 0:06:17 | 0:06:20 | |
-That all sounds very familiar. -Yes, it's funny you should say that, | 0:06:20 | 0:06:23 | |
it's very similar to what we think that early solar system was like. | 0:06:23 | 0:06:27 | |
That there was a disc of material out of which the planets formed, | 0:06:27 | 0:06:30 | |
in that case. | 0:06:30 | 0:06:31 | |
And this is a disc that we can study in detail now. | 0:06:31 | 0:06:34 | |
We can see how things evolve now and then try | 0:06:34 | 0:06:38 | |
and extrapolate to what went on in the early solar system. | 0:06:38 | 0:06:40 | |
So, by studying the rings of Saturn, | 0:06:40 | 0:06:42 | |
we can actually look back to the formation of our whole solar system. | 0:06:42 | 0:06:46 | |
Well, I think that makes this an incredible, powerful picture. | 0:06:46 | 0:06:48 | |
Cos not only is it a beautiful picture of Saturn, | 0:06:48 | 0:06:51 | |
but it's giving us an understanding of our very own origin. | 0:06:51 | 0:06:54 | |
-Well, thank you, that was fantastic. -You're welcome. | 0:06:54 | 0:06:57 | |
Before we leave this astonishing photo, | 0:06:57 | 0:07:00 | |
consider the technology that was used to take it. | 0:07:00 | 0:07:03 | |
Cassini's black-and-white camera has a resolution of | 0:07:04 | 0:07:07 | |
just one megapixel, | 0:07:07 | 0:07:10 | |
a fraction of what you'll find in the average smartphone. | 0:07:10 | 0:07:14 | |
It's only by stitching the photos together | 0:07:14 | 0:07:17 | |
and applying filters that isolate particular wavelengths of light, | 0:07:17 | 0:07:21 | |
that it is possible to make these astonishing colour images. | 0:07:21 | 0:07:26 | |
Art and science, both served by the power of technology. | 0:07:26 | 0:07:29 | |
Our next photograph moves beyond art and science, | 0:07:31 | 0:07:35 | |
to touch the deepest human emotions | 0:07:35 | 0:07:37 | |
and it was captured by a camera even more primitive than Cassini's. | 0:07:37 | 0:07:42 | |
I'm remarkably lucky to be holding this thing in my hands. | 0:07:44 | 0:07:48 | |
It's a flight spare, a copy of the cameras that flew | 0:07:48 | 0:07:51 | |
on the Voyager 1 mission, | 0:07:51 | 0:07:53 | |
one of two spacecraft that were launched in 1977, | 0:07:53 | 0:07:56 | |
towards the outermost planets of the solar system. | 0:07:56 | 0:07:59 | |
It's the same technology that was used in the first video cameras. | 0:07:59 | 0:08:02 | |
And although it looks rather primitive now, | 0:08:02 | 0:08:04 | |
the Voyagers produced some of the most spectacular images | 0:08:04 | 0:08:07 | |
we'd ever seen. | 0:08:07 | 0:08:09 | |
As the Voyager probes flew out through the solar system | 0:08:12 | 0:08:15 | |
in the late '70s and '80s, they sent back amazing pictures. | 0:08:15 | 0:08:20 | |
There was detailed video of Jupiter | 0:08:22 | 0:08:24 | |
and its immense red-spot storm. | 0:08:24 | 0:08:27 | |
And the first close-up images of Jupiter's moons, | 0:08:29 | 0:08:32 | |
revealing Io to be volcanically active | 0:08:32 | 0:08:35 | |
and Europa's icy surface to be covered in mysterious stripes. | 0:08:35 | 0:08:40 | |
The probes flew past Saturn | 0:08:41 | 0:08:44 | |
and then became the first to photograph Uranus and Neptune. | 0:08:44 | 0:08:47 | |
We haven't picked any of those images - | 0:08:50 | 0:08:53 | |
instead we've chosen one taken on Valentine's Day, 1990 - | 0:08:53 | 0:08:57 | |
a time when Voyager 1 was more than six billion kilometres from the sun. | 0:08:57 | 0:09:02 | |
And, at the suggest of the famous planetary scientist Carl Sagan, | 0:09:02 | 0:09:06 | |
it turned to look back in the direction from which it had come | 0:09:06 | 0:09:09 | |
and it took this image. | 0:09:09 | 0:09:11 | |
And, at first, there's not much to see. | 0:09:12 | 0:09:15 | |
You see the blackness of space, a couple of streaks, | 0:09:15 | 0:09:17 | |
which are glare from the sun on the lens. | 0:09:17 | 0:09:19 | |
The sun must be up here somewhere. | 0:09:19 | 0:09:21 | |
But, if you look closer, you see this tiny, pale blue dot, | 0:09:21 | 0:09:25 | |
suspended in one of those sunbeams. | 0:09:25 | 0:09:27 | |
And that is the Earth, seen floating on its own, | 0:09:27 | 0:09:31 | |
amongst the blackness of space. | 0:09:31 | 0:09:33 | |
And no-one caught the emotional impact of that realisation | 0:09:47 | 0:09:51 | |
better than the man | 0:09:51 | 0:09:52 | |
whose idea the picture was. | 0:09:52 | 0:09:55 | |
And this is where we live, on a blue dot. | 0:09:55 | 0:09:59 | |
Consider again that dot. | 0:10:00 | 0:10:02 | |
That's here, that's home, | 0:10:02 | 0:10:06 | |
that's us. | 0:10:06 | 0:10:07 | |
On it, everyone you love, | 0:10:07 | 0:10:10 | |
everyone you know, everyone you ever | 0:10:10 | 0:10:13 | |
heard of, every human being who ever | 0:10:13 | 0:10:16 | |
was lived out their lives on a mote | 0:10:16 | 0:10:19 | |
of dust suspended in a sunbeam. | 0:10:19 | 0:10:23 | |
The Earth is a very small stage | 0:10:24 | 0:10:29 | |
in a vast cosmic arena. | 0:10:29 | 0:10:31 | |
Our third picture was taken 25 years after the pale blue dot, | 0:10:38 | 0:10:43 | |
by the next mission we sent to the outer reaches of the solar system. | 0:10:43 | 0:10:48 | |
Last summer, after a 9½-year journey, | 0:10:49 | 0:10:53 | |
the New Horizon space probe began its approach to Pluto, | 0:10:53 | 0:10:57 | |
a world many expected to be frozen and featureless. | 0:10:57 | 0:11:01 | |
Until then, our highest resolution images of the dwarf plant had | 0:11:01 | 0:11:05 | |
been little more than a fuzzy dot. | 0:11:05 | 0:11:08 | |
Now, we were getting increasingly detailed pictures and, | 0:11:08 | 0:11:12 | |
on the 14th of July, New Horizons | 0:11:12 | 0:11:15 | |
made its closest approach as it flew past Pluto. | 0:11:15 | 0:11:20 | |
For the mission's scientists, there was a nervous wait to see what, | 0:11:20 | 0:11:24 | |
if any, images had been captured by the space craft. | 0:11:24 | 0:11:27 | |
One of those scientists was Carly Howett. | 0:11:27 | 0:11:31 | |
It felt like being five again | 0:11:31 | 0:11:33 | |
and it was Christmas morning | 0:11:33 | 0:11:35 | |
and you knew that there were presents, | 0:11:35 | 0:11:37 | |
but until you actually see what's inside the box, | 0:11:37 | 0:11:40 | |
we didn't really know for sure whether the exposure times | 0:11:40 | 0:11:42 | |
that we'd set were right and all those sorts of things. | 0:11:42 | 0:11:45 | |
So, we were confident in our abilities, | 0:11:45 | 0:11:48 | |
but you're always a little bit nervous. | 0:11:48 | 0:11:50 | |
So, once we started getting the data on the ground, | 0:11:50 | 0:11:52 | |
we knew it was safe and we knew it was good. | 0:11:52 | 0:11:54 | |
And it was like Christmas morning over and over again. | 0:11:54 | 0:11:58 | |
Our third image is this spectacular image of Pluto | 0:11:58 | 0:12:02 | |
taken by New Horizons. | 0:12:02 | 0:12:04 | |
The dwarf planet snapped suddenly into focus | 0:12:06 | 0:12:09 | |
and it was unlike anything | 0:12:09 | 0:12:11 | |
that had been expected. | 0:12:11 | 0:12:13 | |
This image really revolutionised the way that we understood Pluto. | 0:12:14 | 0:12:19 | |
One of the first things that we saw in this image were the mountains. | 0:12:19 | 0:12:22 | |
There are mountains of water ice on Pluto. | 0:12:22 | 0:12:25 | |
They stand about 2½ miles high, | 0:12:25 | 0:12:27 | |
which, for a water ice mountain, is incredibly high. | 0:12:27 | 0:12:30 | |
We wouldn't get that on the Earth, water ice wouldn't be strong | 0:12:30 | 0:12:33 | |
enough, it would collapse under its own weight. | 0:12:33 | 0:12:36 | |
But, at Pluto's cold temperatures, | 0:12:36 | 0:12:37 | |
it's strong enough to maintain that weight. | 0:12:37 | 0:12:40 | |
On closer inspection, some of the mountains held even more surprises. | 0:12:40 | 0:12:45 | |
They have holes in. | 0:12:45 | 0:12:46 | |
And you only get holes in mountains if they're volcanoes. | 0:12:46 | 0:12:49 | |
And so, what we think is going on here is there are cryovolcanoes. | 0:12:49 | 0:12:53 | |
So, not volcanoes in the way that we're used to them, | 0:12:53 | 0:12:56 | |
on Hawaii, with hot rock and lava, | 0:12:56 | 0:12:57 | |
but rather volcanoes that would have emitted ice. | 0:12:57 | 0:13:00 | |
We don't see them being active now, | 0:13:00 | 0:13:02 | |
we don't see any outflow from them at the moment, | 0:13:02 | 0:13:04 | |
we don't know when they were last active, | 0:13:04 | 0:13:06 | |
but there's certainly enough strange terrain around them | 0:13:06 | 0:13:09 | |
to indicate that they must have been active in the near recent past. | 0:13:09 | 0:13:12 | |
But while some areas of Pluto were rugged and mountainous, | 0:13:12 | 0:13:17 | |
in others, such as the large heart-shaped Tombaugh Regio, | 0:13:17 | 0:13:20 | |
the ice was suspiciously smooth. | 0:13:20 | 0:13:23 | |
The left side was known as Sputnik Planum | 0:13:23 | 0:13:26 | |
and this is an interesting region, | 0:13:26 | 0:13:27 | |
because it's incredibly smooth. | 0:13:27 | 0:13:29 | |
But, when we zoom in, you can | 0:13:29 | 0:13:31 | |
see there's a lot of complicated structure in this region. | 0:13:31 | 0:13:33 | |
And you can see there's all of this structure in the cells itself. | 0:13:33 | 0:13:37 | |
But you can see how different this terrain is when you get | 0:13:37 | 0:13:40 | |
up against the bedrock, if you like, of the surrounding regions. | 0:13:40 | 0:13:44 | |
Now, the smoothness is very strange. | 0:13:44 | 0:13:47 | |
Everywhere is bombarded by meteorites, | 0:13:47 | 0:13:49 | |
these are called impact craters. | 0:13:49 | 0:13:51 | |
And so what is going on in this region of Pluto to eradicate | 0:13:51 | 0:13:54 | |
those impact craters? There's several ideas about this. | 0:13:54 | 0:13:57 | |
The prominent idea is that this is made of mostly nitrogen | 0:13:57 | 0:14:00 | |
and carbon monoxide. | 0:14:00 | 0:14:02 | |
These are quite soft and so | 0:14:02 | 0:14:04 | |
we don't think a lot of heat is needed to get these ices moving. | 0:14:04 | 0:14:08 | |
The heating that Pluto still has from its core is able to | 0:14:08 | 0:14:12 | |
circulate those ices. | 0:14:12 | 0:14:14 | |
So, if you had an impact here, it wouldn't take long before this | 0:14:14 | 0:14:17 | |
overturning eradicated any evidence for it. | 0:14:17 | 0:14:21 | |
So, this image really has revolutionised | 0:14:21 | 0:14:23 | |
our understanding of both Pluto and the outer solar system. | 0:14:23 | 0:14:27 | |
Before we got there, we knew something of its bulk | 0:14:27 | 0:14:30 | |
composition, but we didn't know about its complex geology. | 0:14:30 | 0:14:33 | |
And we certainly didn't think that it was geologically active. | 0:14:33 | 0:14:36 | |
This has huge implications, | 0:14:36 | 0:14:37 | |
not only for our understanding of Pluto and its evolution | 0:14:37 | 0:14:40 | |
and its composition, but also for other, | 0:14:40 | 0:14:43 | |
similar bodies in the outer solar system. | 0:14:43 | 0:14:45 | |
Before we reach our next photo, let's delve back | 0:14:51 | 0:14:55 | |
into the history of our attempts to photograph the solar system. | 0:14:55 | 0:14:59 | |
We've only been sending probes to the planets for 50 years. | 0:15:00 | 0:15:04 | |
But, as Pete Lawrence has been finding out, | 0:15:04 | 0:15:06 | |
the art of astrophotography is much, much older. | 0:15:06 | 0:15:10 | |
The technology found in digital cameras today has come | 0:15:12 | 0:15:15 | |
directly from astronomy. | 0:15:15 | 0:15:17 | |
In fact, the sensors, like the one I'm using here and the ones found in | 0:15:17 | 0:15:21 | |
digital cameras and smartphones are descended from those | 0:15:21 | 0:15:24 | |
developed by NASA for interplanetary spacecraft. | 0:15:24 | 0:15:28 | |
And the desire to take pictures of the sky has a long | 0:15:28 | 0:15:31 | |
history in helping develop photographic techniques. | 0:15:31 | 0:15:35 | |
In fact, even before they were taking photographs of people, | 0:15:35 | 0:15:38 | |
photographers were taking pictures of the sky. | 0:15:38 | 0:15:42 | |
The earliest photographs, called Daguerreotypes, were taken on | 0:15:42 | 0:15:45 | |
chemically-coated sheets of copper and developed using mercury fumes. | 0:15:45 | 0:15:50 | |
However, these weren't very sensitive | 0:15:50 | 0:15:52 | |
and could only capture the very brightest objects in the sky. | 0:15:52 | 0:15:56 | |
So, photographers and astronomers | 0:15:56 | 0:15:59 | |
came up with a series of new techniques. | 0:15:59 | 0:16:02 | |
I've come to the Observatory Science Centre, in Herstmonceux, | 0:16:02 | 0:16:06 | |
where astronomers have been imaging the sky for 150 years to try | 0:16:06 | 0:16:10 | |
out one of those old techniques. | 0:16:10 | 0:16:13 | |
This is Guy Paterson, | 0:16:13 | 0:16:15 | |
an artist who specialises in historic photographic methods. | 0:16:15 | 0:16:19 | |
Hi, Guy. | 0:16:19 | 0:16:20 | |
-Hi. -Nice to meet you. This looks quite interesting. | 0:16:20 | 0:16:23 | |
What's going on here? | 0:16:23 | 0:16:24 | |
We're going to attempt to get a shot of the moon, | 0:16:24 | 0:16:27 | |
-using a very old process called wet plate collodion. -Right. | 0:16:27 | 0:16:31 | |
So, what have you got to do then, to make this work? | 0:16:31 | 0:16:34 | |
OK, so, we're going to start off by putting on these protective gloves, | 0:16:34 | 0:16:38 | |
cos silver nitrate tends to stain anything organic for several | 0:16:38 | 0:16:43 | |
days if you use it. We have our plate, | 0:16:43 | 0:16:46 | |
it comes with a protective film over the surface we want to use. | 0:16:46 | 0:16:50 | |
So, we're going to peel that off. | 0:16:50 | 0:16:52 | |
-So, I'm going to pour on the collodion. -OK. | 0:16:53 | 0:16:57 | |
It's completely away from the sanitisation of using digital kit, | 0:16:57 | 0:17:01 | |
where you just press a button and the image appears on the back of it. | 0:17:01 | 0:17:04 | |
That's right. I think that's a lot of the appeal, actually, | 0:17:04 | 0:17:07 | |
you're completely in control of the situation. | 0:17:07 | 0:17:11 | |
If it goes well... | 0:17:11 | 0:17:12 | |
PETE LAUGHS | 0:17:12 | 0:17:14 | |
Right, so, now we're ready for it to go into the silver nitrate solution. | 0:17:14 | 0:17:19 | |
-OK. -And we lower it in there, carefully. | 0:17:19 | 0:17:23 | |
That makes it light sensitive after that point. | 0:17:23 | 0:17:26 | |
I guess the lights have got to go out now, | 0:17:26 | 0:17:28 | |
so that we can get the plate onto the back of the telescope. | 0:17:28 | 0:17:31 | |
That's right. | 0:17:31 | 0:17:33 | |
And try and capture a picture of that moon, which is | 0:17:33 | 0:17:37 | |
shining brightly out there, perfect for us. | 0:17:37 | 0:17:40 | |
Five, four, three, two, one. | 0:17:40 | 0:17:46 | |
And here is our plate. Nothing to see at the moment. | 0:17:51 | 0:17:55 | |
Now we're going to develop, which we do just pouring the solution on. | 0:17:55 | 0:18:02 | |
-So, this takes about 15 seconds, you say? -That's right. | 0:18:03 | 0:18:08 | |
Just stop the development by pouring water over it. | 0:18:08 | 0:18:13 | |
-Finally. -It's the moment of truth. | 0:18:13 | 0:18:16 | |
Oh, look at that. | 0:18:18 | 0:18:20 | |
So, now you've rinsed it off, is it OK to turn the lights back on? | 0:18:20 | 0:18:23 | |
-Yeah, it should be absolutely fine. -OK. | 0:18:23 | 0:18:26 | |
This is amazing and just how it used to be done. | 0:18:30 | 0:18:34 | |
The plate is actually quite small, but | 0:18:34 | 0:18:37 | |
when you look at it closely, you can see there's loads of detail on it. | 0:18:37 | 0:18:41 | |
And, to be honest, I'm actually quite surprised that this old | 0:18:41 | 0:18:44 | |
technology is able to produce something as sharp as this. | 0:18:44 | 0:18:48 | |
Quite amazing. | 0:18:48 | 0:18:51 | |
So far, we have seen three of our five images. | 0:18:51 | 0:18:54 | |
A portrait of the whole Saturn system, | 0:18:55 | 0:18:58 | |
a distant view of planet Earth | 0:18:58 | 0:19:01 | |
and a revolutionary image of Pluto. | 0:19:01 | 0:19:04 | |
Our next image may seem plain by comparison. | 0:19:05 | 0:19:08 | |
It's a picture of Gale Crater on the surface of Mars. | 0:19:09 | 0:19:13 | |
But this photo is special, because it shows with incredible accuracy | 0:19:14 | 0:19:19 | |
what it would be like to stand on the surface of another world. | 0:19:19 | 0:19:22 | |
It was taken by one of the most advanced pieces of equipment | 0:19:34 | 0:19:37 | |
we've ever sent into space. | 0:19:37 | 0:19:39 | |
The Curiosity Rover that was lowered onto | 0:19:44 | 0:19:47 | |
the surface of Mars in August 2012. | 0:19:47 | 0:19:51 | |
Amongst its suite of scientific instruments, | 0:19:51 | 0:19:54 | |
Curiosity is equipped with a camera mounted on a mast at head height. | 0:19:54 | 0:19:59 | |
This particular image was created by painstakingly assembling more | 0:20:01 | 0:20:06 | |
than 70 frames from that camera into a single high-resolution panorama. | 0:20:06 | 0:20:11 | |
The colours have been adjusted to render them | 0:20:12 | 0:20:15 | |
as close as possible to what our eyes would see. | 0:20:15 | 0:20:19 | |
It is the work of artist Michael Benson. | 0:20:19 | 0:20:21 | |
-So, this is sort of a human eye view of the Martian surface. -Yeah. | 0:20:21 | 0:20:25 | |
Exactly, and what I'm trying to achieve with a lot of these images, | 0:20:25 | 0:20:30 | |
most of these images, is to give people a sense of what it | 0:20:30 | 0:20:33 | |
might look like if we could actually go. | 0:20:33 | 0:20:36 | |
So, why is it important to let people see images like this? | 0:20:36 | 0:20:39 | |
I think that we, on Earth, | 0:20:39 | 0:20:41 | |
spend too much time in our self-absorbed concerns, you know? | 0:20:41 | 0:20:47 | |
I would surmise that it might be useful | 0:20:47 | 0:20:49 | |
if we looked up a little more and understood that we belong, | 0:20:49 | 0:20:52 | |
that the Earth belongs, to a suite of landscapes, | 0:20:52 | 0:20:54 | |
orbiting the same source of light, the sun. | 0:20:54 | 0:20:58 | |
Some of them very alien, sci-fi, you know, Jupiter. | 0:20:58 | 0:21:04 | |
And some of them are very close to what we might see... | 0:21:04 | 0:21:06 | |
I mean, they're very Earth-like in some ways. This one, | 0:21:06 | 0:21:09 | |
for example, it looks like Utah or Arizona. | 0:21:09 | 0:21:11 | |
And you can see this connection between Mars and our planet. | 0:21:11 | 0:21:17 | |
Those are the so-called terrestrial planets, those with hard surfaces | 0:21:17 | 0:21:20 | |
-in the inner solar system. -Yeah. -So, that's part of what I'm trying | 0:21:20 | 0:21:26 | |
-to convey with this work. -So, this could be Earth, but it's not. | 0:21:26 | 0:21:31 | |
This is another planet, out there. | 0:21:31 | 0:21:33 | |
-But the sky gives it away, doesn't it? -Yes, that does look alien. | 0:21:33 | 0:21:36 | |
-Yeah, yeah, yeah. -Well, I think it gives everyone an opportunity to | 0:21:36 | 0:21:39 | |
stand on the surface of Mars and to me, that's a great achievement. | 0:21:39 | 0:21:42 | |
-Thank you very much. -Thank you. -I appreciate it. | 0:21:42 | 0:21:46 | |
But, as awe-inspiring as this picture is, | 0:21:46 | 0:21:48 | |
there's a great deal more to it than its aesthetic appeal. | 0:21:48 | 0:21:52 | |
The primary purpose of imaging the planets is to provide | 0:21:52 | 0:21:55 | |
scientific value. | 0:21:55 | 0:21:58 | |
And in that one image of Gale Crater, there's an amazing | 0:21:58 | 0:22:00 | |
wealth of detail about the geological history of Mars. | 0:22:00 | 0:22:04 | |
I've come downstairs in the museum to find Dr Joe Michalski, | 0:22:06 | 0:22:11 | |
a planetary geologist who uses images from spacecraft to study | 0:22:11 | 0:22:16 | |
the geological past of Mars. | 0:22:16 | 0:22:19 | |
So, when I look at this image, I see a landscape | 0:22:20 | 0:22:23 | |
and I can imagine being there. | 0:22:23 | 0:22:25 | |
But, as a geologist, what do you get from images like this one? | 0:22:25 | 0:22:28 | |
Well, the first thing we think about is context. | 0:22:28 | 0:22:30 | |
The important thing here is that this is the floor of a huge | 0:22:30 | 0:22:35 | |
impact crater. Those craters, effectively, | 0:22:35 | 0:22:37 | |
are basins where sedimentary rocks accumulate from various processes. | 0:22:37 | 0:22:41 | |
-Cos it's an old impact crater? -Yeah, about four billion years old. | 0:22:41 | 0:22:45 | |
And the rocks within it are also old, | 0:22:45 | 0:22:47 | |
but 500 million years younger than that. So, a lot is going on there. | 0:22:47 | 0:22:51 | |
OK, so what should I be looking at, if I want to be a Martian geologist? | 0:22:51 | 0:22:54 | |
-Where do we start? -So, if you look at the top of the image, | 0:22:54 | 0:22:57 | |
that's the edge of Mount Sharp. | 0:22:57 | 0:23:00 | |
You can see layered rocks that are nearly horizontal. | 0:23:00 | 0:23:02 | |
Yeah, there's this, sort of, stripeyness to it. | 0:23:02 | 0:23:05 | |
Yeah, so those are rock beds, strata, | 0:23:05 | 0:23:08 | |
that formed probably through air-fall of volcanic ash or dust. | 0:23:08 | 0:23:11 | |
And that's accumulated over millions of years | 0:23:11 | 0:23:14 | |
and that's why it forms layers. | 0:23:14 | 0:23:15 | |
Then, beneath that, you can | 0:23:15 | 0:23:17 | |
see there are these other units that don't form as prominent topography. | 0:23:17 | 0:23:21 | |
The bluish and the light brown. | 0:23:21 | 0:23:23 | |
So, the fact that it does not form these big buttes tells me | 0:23:23 | 0:23:27 | |
that it's a softer unit. And, so, | 0:23:27 | 0:23:30 | |
if we were able to investigate the mineralogy of that, it might | 0:23:30 | 0:23:32 | |
be something that, for example, contains clay minerals or sulphates. | 0:23:32 | 0:23:37 | |
So, those are minerals that formed in water, but they're softer. | 0:23:37 | 0:23:40 | |
So, part of the evidence that there was some water here or some | 0:23:40 | 0:23:43 | |
dampness here is the fact that you have clay and these other things? | 0:23:43 | 0:23:47 | |
That's right. In between is this unit, | 0:23:47 | 0:23:50 | |
which is just composed of gravel and sand and dust. | 0:23:50 | 0:23:54 | |
Those are common deposits on Mars, | 0:23:54 | 0:23:57 | |
where you've got a little bit of fluvial activity. | 0:23:57 | 0:24:01 | |
-That's river-like, right? Or water. -Yeah, exactly. | 0:24:01 | 0:24:04 | |
So, when we look at this image, we see a landscape partly | 0:24:04 | 0:24:07 | |
shaped by water. | 0:24:07 | 0:24:09 | |
And the crater's 5km deep, | 0:24:09 | 0:24:11 | |
so should I be imagining a big, deep lake? Was the crater full of water? | 0:24:11 | 0:24:15 | |
As we've investigated this further, it seems that no, | 0:24:15 | 0:24:18 | |
it probably wasn't ever filled like that. | 0:24:18 | 0:24:20 | |
But, certainly, there was water here. | 0:24:20 | 0:24:22 | |
There were small lakes that came | 0:24:22 | 0:24:24 | |
and went at the scale of thousands of years. | 0:24:24 | 0:24:27 | |
It seems like a lot to a human, but geologically, it's a snapshot. | 0:24:27 | 0:24:30 | |
It's amazing to me how much you can tell from this one image, | 0:24:30 | 0:24:33 | |
but, of course, that's the beauty of these images of other worlds. | 0:24:33 | 0:24:36 | |
They're not just beautiful things to look at, they're data as well. | 0:24:36 | 0:24:41 | |
Yeah, that's right. | 0:24:41 | 0:24:42 | |
Every single image is packed with scientific information. | 0:24:42 | 0:24:45 | |
-Joe, thank you very much. -Thanks. | 0:24:45 | 0:24:47 | |
That brings us to our last image, which is | 0:24:51 | 0:24:54 | |
a bit different to our others, because even I haven't seen it yet. | 0:24:54 | 0:24:56 | |
It's only just been taken. | 0:24:56 | 0:24:59 | |
Via this NASA website I can access data from a satellite called | 0:24:59 | 0:25:02 | |
the Solar Dynamics Observatory, which sits 36,000km away | 0:25:02 | 0:25:07 | |
from Earth staring at the sun and sending its data back. | 0:25:07 | 0:25:10 | |
This is its most recent image, taken just ten minutes ago. | 0:25:10 | 0:25:14 | |
It's not the view of the sun we're used to, | 0:25:14 | 0:25:16 | |
it's not a featureless yellow disc. | 0:25:16 | 0:25:19 | |
This is the sun in the ultraviolet. | 0:25:19 | 0:25:21 | |
The Solar Dynamics Observatory captures images using | 0:25:29 | 0:25:32 | |
light in ten different wavelengths. | 0:25:32 | 0:25:35 | |
It reveals the sun to be a very different | 0:25:36 | 0:25:39 | |
beast from the featureless, golden disc we're used to seeing. | 0:25:39 | 0:25:43 | |
It shows the surface to be incredibly active, | 0:25:44 | 0:25:48 | |
bursting with flares and massive explosions of super-heated plasma. | 0:25:48 | 0:25:53 | |
This is the true face of our sun. | 0:25:53 | 0:25:56 | |
I never get tired of seeing the sun like this. | 0:25:57 | 0:26:00 | |
It's not just a boring, yellow disc, it's a dynamic and active world. | 0:26:00 | 0:26:04 | |
There are wonderful features in its atmosphere | 0:26:04 | 0:26:06 | |
and the disc itself is a turbulent, boiling mass of gas. | 0:26:06 | 0:26:11 | |
And we can see all of that because we're looking in the ultraviolet. | 0:26:11 | 0:26:14 | |
And that's one of the reasons we chose this image, it | 0:26:14 | 0:26:17 | |
demonstrates that by going beyond the light that our human eyes | 0:26:17 | 0:26:20 | |
are sensitive to, we can get much more information about the cosmos. | 0:26:20 | 0:26:24 | |
The Solar Dynamics Observatory actually images the sun once | 0:26:26 | 0:26:30 | |
every ten seconds, | 0:26:30 | 0:26:33 | |
giving us a real-time view of the star that allows us | 0:26:33 | 0:26:36 | |
to trace the source of its surface activity. | 0:26:36 | 0:26:38 | |
In some wavelengths, we can see dark sunspots on this surface. | 0:26:39 | 0:26:44 | |
But in other wavelengths, we can see that those dark spots | 0:26:44 | 0:26:48 | |
are the sites for the greatest solar activity. | 0:26:48 | 0:26:51 | |
Where arcs of plasma burst from the surface along the twisted | 0:26:53 | 0:26:57 | |
magnetic field lines of the sun. | 0:26:57 | 0:26:59 | |
And that's important, | 0:27:01 | 0:27:02 | |
because activity on the sun has a tremendous affect on the Earth. | 0:27:02 | 0:27:06 | |
The activity on the sun's surface creates what is known as | 0:27:08 | 0:27:11 | |
space weather. | 0:27:11 | 0:27:14 | |
The flares and ejections from the surface | 0:27:14 | 0:27:17 | |
send streams of charged particles shooting out into space. | 0:27:17 | 0:27:20 | |
If they hit the earth, they create quite an effect. | 0:27:22 | 0:27:26 | |
Causing aurorae, like the Northern and Southern Lights. | 0:27:26 | 0:27:30 | |
But those solar storms can also cause severe damage to the | 0:27:30 | 0:27:34 | |
electrics of satellites and even interrupt power supplies on Earth. | 0:27:34 | 0:27:38 | |
And that is why the Solar Dynamics Observatory images are so important. | 0:27:39 | 0:27:44 | |
It is hoped that the information embedded in these brilliant images | 0:27:44 | 0:27:48 | |
will give us an understanding on the causes | 0:27:48 | 0:27:51 | |
and variety of solar activity, helping us to predict | 0:27:51 | 0:27:55 | |
space weather and finding out when solar storms | 0:27:55 | 0:27:57 | |
are heading towards Earth. | 0:27:57 | 0:28:00 | |
So, that's it, our choices for the top five solar system photos. | 0:28:01 | 0:28:04 | |
And if you think we've missed something or if you disagree, | 0:28:04 | 0:28:07 | |
you can use Twitter to let us know. | 0:28:07 | 0:28:09 | |
But whatever your favourite images, you can agree, I'm sure, | 0:28:09 | 0:28:12 | |
that we've come a long way | 0:28:12 | 0:28:13 | |
since this wonderful image of the moon taken almost 160 years ago. | 0:28:13 | 0:28:17 | |
We really have. | 0:28:17 | 0:28:19 | |
And that's all we have time for this month. | 0:28:21 | 0:28:24 | |
Next month, we'll be joined by Stephen Hawking to explore | 0:28:24 | 0:28:28 | |
the recent discovery of gravitational waves | 0:28:28 | 0:28:30 | |
and what they can tell us about black holes. | 0:28:30 | 0:28:33 | |
In the meantime, get outside and get looking up. | 0:28:34 | 0:28:38 | |
Goodnight. | 0:28:38 | 0:28:39 |