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When we look up at the cosmos, | 0:00:02 | 0:00:04 | |
we see a universe that's filled with billions and billons of galaxies, | 0:00:04 | 0:00:08 | |
each of them home to billions and billions of stars | 0:00:08 | 0:00:12 | |
shining back down upon us. | 0:00:12 | 0:00:14 | |
But despite the vastness... | 0:00:16 | 0:00:18 | |
from here, it looks a lonely place. | 0:00:18 | 0:00:20 | |
Are we the only life that looks up at the sky at night? | 0:00:22 | 0:00:25 | |
Or somewhere else, around some other twinkling star, | 0:00:25 | 0:00:29 | |
are there other beings doing the same? | 0:00:29 | 0:00:32 | |
Remarkably, we're making progress towards answering that question. | 0:00:34 | 0:00:38 | |
In the last few years, we've discovered our galaxy | 0:00:38 | 0:00:40 | |
is teeming with planets, | 0:00:40 | 0:00:42 | |
alien worlds in almost unimaginable variety. | 0:00:42 | 0:00:45 | |
And for the first time, | 0:00:45 | 0:00:46 | |
we're actually getting a glimpse of what these worlds are really like. | 0:00:46 | 0:00:49 | |
But the question is, can any of them harbour life? | 0:00:49 | 0:00:52 | |
Come with us on a journey through the galaxy | 0:00:52 | 0:00:55 | |
as we hunt for ET. | 0:00:55 | 0:00:56 | |
Welcome to The Sky At Night. | 0:00:56 | 0:00:58 | |
Our search for alien life doesn't have to be limited | 0:01:24 | 0:01:27 | |
to waiting for extraterrestrials to give us a call, | 0:01:27 | 0:01:30 | |
new astronomical techniques have enabled amazing discoveries, | 0:01:30 | 0:01:33 | |
taking us closer to finding life out there than we've ever been. | 0:01:33 | 0:01:37 | |
Some of the most advanced work in studying alien atmospheres | 0:01:37 | 0:01:40 | |
is done here at Exeter University. | 0:01:40 | 0:01:42 | |
In this programme, we're going to be pushing at the boundaries of science | 0:01:42 | 0:01:45 | |
in the search for alien life. | 0:01:45 | 0:01:47 | |
Coming up, how do we define life | 0:01:47 | 0:01:50 | |
and would we recognise it if we saw it? | 0:01:50 | 0:01:52 | |
Adam Rutherford investigates. | 0:01:52 | 0:01:54 | |
So, when we look at other atmospheres, | 0:01:56 | 0:01:58 | |
if we see CFCs in their atmospheres, then we know | 0:01:58 | 0:02:01 | |
there's some kind of a technological civilisation on that planet. | 0:02:01 | 0:02:03 | |
These are sunsets, seen from other planets, | 0:02:03 | 0:02:08 | |
orbiting distant stars. | 0:02:08 | 0:02:11 | |
What can they tell us | 0:02:11 | 0:02:12 | |
about the potential for extraterrestrial life? | 0:02:12 | 0:02:15 | |
And how many alien civilisations could there be out there? | 0:02:17 | 0:02:21 | |
If we looked up into the night sky, | 0:02:21 | 0:02:23 | |
we'd expect to see five, and that includes us, | 0:02:23 | 0:02:25 | |
so we'd actually expect to see four. | 0:02:25 | 0:02:27 | |
Plus, as autumn comes upon us, | 0:02:29 | 0:02:30 | |
Pete is looking at one of the great spectacles of the night sky - | 0:02:30 | 0:02:35 | |
Andromeda. | 0:02:35 | 0:02:37 | |
If we want to discover life beyond our solar system, | 0:02:41 | 0:02:43 | |
there are certain things we should look for, | 0:02:43 | 0:02:45 | |
and the first is a planet - | 0:02:45 | 0:02:47 | |
preferably one rather like the Earth, with liquid water, | 0:02:47 | 0:02:50 | |
continents and a nice atmosphere. | 0:02:50 | 0:02:52 | |
And this hunt for extrasolar planets, or exoplanets, | 0:02:52 | 0:02:55 | |
is beginning to pay off. | 0:02:55 | 0:02:57 | |
Until 1995, despite decades of searching, | 0:02:58 | 0:03:01 | |
our solar system was the only one that we knew about. | 0:03:01 | 0:03:05 | |
Then, suddenly, everything changed | 0:03:07 | 0:03:09 | |
when two astronomers in Geneva | 0:03:09 | 0:03:11 | |
announced the discovery of this planet. | 0:03:11 | 0:03:13 | |
Rapidly orbiting, and weighing about half the mass of Jupiter, | 0:03:13 | 0:03:17 | |
It goes round the star 51 Pegasi, just 50 light years from Earth. | 0:03:17 | 0:03:21 | |
But since then, the discoveries have come thick and fast | 0:03:23 | 0:03:25 | |
and we've found all sorts of unexpected planets. | 0:03:25 | 0:03:28 | |
Then there's HD 209458b, a planet larger than Jupiter, | 0:03:29 | 0:03:35 | |
which is so close to its parent star that it's losing its atmosphere. | 0:03:35 | 0:03:39 | |
More than 10,000 tonnes a second of hydrogen is swept off | 0:03:39 | 0:03:43 | |
in a long train, rather like a comet's tail. | 0:03:43 | 0:03:47 | |
And just over 150 light years from Earth, | 0:03:47 | 0:03:50 | |
there's a planet in a system with three suns, | 0:03:50 | 0:03:53 | |
creating this astonishing sight from a hypothetical moon. | 0:03:53 | 0:03:57 | |
But none of these exotic worlds could support life. | 0:03:57 | 0:04:00 | |
What we need is a planet in the Goldilocks zone. | 0:04:00 | 0:04:03 | |
Not too hot and not too cold, but just right. | 0:04:03 | 0:04:06 | |
Able to support liquid water | 0:04:06 | 0:04:08 | |
and therefore maybe life on its surface. | 0:04:08 | 0:04:10 | |
We have found a number of planets that should be rocky. | 0:04:10 | 0:04:15 | |
But the candidate that's closest to our own Earth is this one, | 0:04:15 | 0:04:18 | |
Kepler 186f. | 0:04:18 | 0:04:21 | |
It was discovered in April this year | 0:04:21 | 0:04:23 | |
and is the first planet we've found that's close in size to Earth | 0:04:23 | 0:04:26 | |
and that's the right distance from its sun to maybe harbour life. | 0:04:26 | 0:04:30 | |
In total, we've now discovered 1,516 exoplanets, | 0:04:33 | 0:04:38 | |
nearly half of them in the past year, | 0:04:38 | 0:04:40 | |
and the hunt continues. | 0:04:40 | 0:04:42 | |
So, we can find alien worlds, | 0:04:44 | 0:04:46 | |
but what about the aliens themselves? | 0:04:46 | 0:04:48 | |
Do any of these planets harbour life? | 0:04:48 | 0:04:51 | |
It's a tantalizing question, | 0:04:51 | 0:04:53 | |
and I wonder, even if we found life, would we recognise it? | 0:04:53 | 0:04:57 | |
Adam Rutherford is investigating. | 0:04:57 | 0:04:59 | |
Everywhere you look on our planet, there is life, | 0:05:05 | 0:05:09 | |
and it comes in all shapes and sizes. | 0:05:09 | 0:05:13 | |
From the tiniest bacteria, to the blue whale, | 0:05:13 | 0:05:17 | |
to the fungi that spreads over hundreds of acres, | 0:05:17 | 0:05:21 | |
there seems to be an almost endless variety to life on Earth. | 0:05:21 | 0:05:25 | |
And this astonishing variety raises a really interesting question... | 0:05:25 | 0:05:30 | |
how do we actually define life? | 0:05:30 | 0:05:33 | |
This is a question we really have to answer | 0:05:35 | 0:05:38 | |
if we want to look for life off-world. | 0:05:38 | 0:05:40 | |
We instinctively understand what life is, | 0:05:42 | 0:05:45 | |
we know it when we see it. | 0:05:45 | 0:05:47 | |
The tree is alive but the clouds above are not. | 0:05:47 | 0:05:50 | |
But codifying these differences isn't easy. | 0:05:53 | 0:05:56 | |
What's needed are a series of testable criteria | 0:05:56 | 0:06:00 | |
that fit all living things and exclude all non-living things. | 0:06:00 | 0:06:04 | |
One way is to look at how life behaves. | 0:06:06 | 0:06:08 | |
There are certain behaviours that all life seems to display, | 0:06:11 | 0:06:14 | |
such as movement, growth, respiration, | 0:06:14 | 0:06:18 | |
and, in particular, reproduction. | 0:06:18 | 0:06:21 | |
But these characteristics might not always be exclusive to life. | 0:06:21 | 0:06:26 | |
Take a flame, for example. | 0:06:30 | 0:06:31 | |
It starts with a spark. | 0:06:31 | 0:06:33 | |
And as the flame gets bigger and bigger, it consumes fuel | 0:06:36 | 0:06:39 | |
in the form of oxygen from the air and carbon from the wick. | 0:06:39 | 0:06:43 | |
If you blow on it... | 0:06:43 | 0:06:45 | |
it responds and it produces wastes in the form of smoke and gas. | 0:06:45 | 0:06:50 | |
Now, these are all the types of things that we associate | 0:06:50 | 0:06:52 | |
with living organisms, | 0:06:52 | 0:06:54 | |
and it also does something which is a lot like reproducing. | 0:06:54 | 0:06:57 | |
You can use one flame... | 0:06:57 | 0:07:00 | |
to create another... | 0:07:00 | 0:07:02 | |
and another... | 0:07:02 | 0:07:04 | |
..and another... | 0:07:05 | 0:07:07 | |
and so on. | 0:07:07 | 0:07:09 | |
So, the question is... | 0:07:10 | 0:07:12 | |
is a flame alive? | 0:07:12 | 0:07:14 | |
Of course, the answer to this is no. | 0:07:16 | 0:07:19 | |
One of the reasons is that the flame doesn't contain any information, | 0:07:19 | 0:07:23 | |
and information seems to be a key characteristic of life. | 0:07:23 | 0:07:28 | |
All life reproduces itself, and when it does so, it passes on information | 0:07:28 | 0:07:32 | |
from generation to generation. | 0:07:32 | 0:07:35 | |
Now, that information is encoded in DNA. | 0:07:35 | 0:07:38 | |
Every time a cell divides, it passes it on from cell to cell, | 0:07:38 | 0:07:42 | |
from parent to offspring. | 0:07:42 | 0:07:44 | |
But does the presence of DNA define what life is | 0:07:46 | 0:07:50 | |
everywhere in the universe? | 0:07:50 | 0:07:52 | |
Well, for me, the answer is no. | 0:07:55 | 0:07:58 | |
Yes, DNA is universal amongst all living things on Earth, | 0:07:58 | 0:08:03 | |
but it doesn't help us to understand how life began in the first place. | 0:08:03 | 0:08:08 | |
It misses a key process that makes living things 'alive'. | 0:08:08 | 0:08:12 | |
DNA replication requires energy, | 0:08:12 | 0:08:14 | |
and when we look at how cells generate that energy, | 0:08:14 | 0:08:17 | |
it is a more fundamental process than replication. | 0:08:17 | 0:08:21 | |
Whilst DNA is how life replicates here on Earth, | 0:08:22 | 0:08:26 | |
it might not be the case elsewhere. | 0:08:26 | 0:08:29 | |
But there is a process that should be universal. | 0:08:29 | 0:08:32 | |
Life is a chemical reaction, a process of extracting energy | 0:08:35 | 0:08:39 | |
from the environment and using it to sustain itself - | 0:08:39 | 0:08:43 | |
a process we call metabolism - | 0:08:43 | 0:08:46 | |
and this is the key to defining life. | 0:08:46 | 0:08:49 | |
You can see it in action here in the lab. | 0:08:52 | 0:08:54 | |
In this jar is some water and a plant called egeria. | 0:08:57 | 0:09:00 | |
Now, the plant consumes energy in the form of light | 0:09:00 | 0:09:04 | |
and uses it in the production of glucose. | 0:09:04 | 0:09:07 | |
Now, as a by-product of that metabolic process, | 0:09:07 | 0:09:10 | |
it produces oxygen, and, if we look very closely, | 0:09:10 | 0:09:13 | |
we should be able to see tiny bubbles of oxygen | 0:09:13 | 0:09:16 | |
coming off the plant. | 0:09:16 | 0:09:17 | |
There you go. | 0:09:17 | 0:09:19 | |
Now, this is a process that all plants do. | 0:09:19 | 0:09:21 | |
It's called photosynthesis. | 0:09:21 | 0:09:23 | |
They extract energy from the environment to create something new - | 0:09:23 | 0:09:26 | |
in this case, using light to convert carbon dioxide and water | 0:09:26 | 0:09:31 | |
into sugars, and then the plant uses that sugar | 0:09:31 | 0:09:34 | |
to power complex living processes. | 0:09:34 | 0:09:37 | |
Without metabolism, there would be no energy to sustain life, | 0:09:38 | 0:09:42 | |
and no energy to reproduce. | 0:09:42 | 0:09:45 | |
And luckily, metabolism leaves a trail of evidence behind it. | 0:09:45 | 0:09:49 | |
In fact, the oxygen that fills our atmosphere was created by life. | 0:09:49 | 0:09:54 | |
So, forget about radio signals from ET. | 0:09:55 | 0:09:59 | |
If we really want to find signs of life, | 0:09:59 | 0:10:01 | |
we should be looking at the atmospheres of exoplanets. | 0:10:01 | 0:10:04 | |
And it's possible to do this by analysing light that passes through | 0:10:04 | 0:10:08 | |
the atmospheres of distant planets to reveal what they are made of. | 0:10:08 | 0:10:13 | |
To understand what signs we should look out for, | 0:10:13 | 0:10:16 | |
I'm meeting Louisa Preston. | 0:10:16 | 0:10:17 | |
If we were to look at the Earth from space, | 0:10:18 | 0:10:21 | |
would we be able to tell that there is life on Earth? | 0:10:21 | 0:10:24 | |
Yes, we would be able to see oxygen, methane, carbon dioxide... | 0:10:24 | 0:10:29 | |
We also can look at the Earth whilst we're standing on it. | 0:10:29 | 0:10:32 | |
The sunlight hits the atmosphere of the Earth, | 0:10:32 | 0:10:34 | |
and it gets reflected away, | 0:10:34 | 0:10:36 | |
and it hits the moon and then the moon reflects it back to us, | 0:10:36 | 0:10:39 | |
so we can observe ourselves. It's called earthshine. | 0:10:39 | 0:10:41 | |
So, we look at the moon and we can tell that there's life on Earth? | 0:10:41 | 0:10:45 | |
Yes! | 0:10:45 | 0:10:46 | |
How do we then transfer that into looking for life | 0:10:46 | 0:10:49 | |
in exoplanets, in other planets? | 0:10:49 | 0:10:51 | |
Well, because we know that the atmosphere | 0:10:51 | 0:10:54 | |
can harbour these different types of molecules that life creates, | 0:10:54 | 0:10:57 | |
we can look for exactly the same thing when we look at exoplanets, | 0:10:57 | 0:11:00 | |
but we just have to figure out what the exact right molecules are. | 0:11:00 | 0:11:03 | |
So, oxygen is definitely a by-signature that we would look for | 0:11:03 | 0:11:06 | |
on another planet. | 0:11:06 | 0:11:07 | |
The problem is, it can be made from non-biological ways, | 0:11:07 | 0:11:10 | |
same with methane, | 0:11:10 | 0:11:12 | |
so we have to be careful of these false positives, as we call them. | 0:11:12 | 0:11:14 | |
So, is it that we're looking for a particular combination | 0:11:14 | 0:11:17 | |
of those gases in the atmosphere? | 0:11:17 | 0:11:19 | |
The right amount of methane, the right amount of oxygen... | 0:11:19 | 0:11:22 | |
Sure. It's not the right amount, exactly. | 0:11:22 | 0:11:25 | |
It's more a disequilibrium idea. | 0:11:25 | 0:11:27 | |
There could be a bit of oxygen, there could be a bit of methane, | 0:11:27 | 0:11:30 | |
but we want to see an excessive amount, because oxygen and methane | 0:11:30 | 0:11:33 | |
are very short lived. They can degrade very quickly, | 0:11:33 | 0:11:35 | |
react with other products, react with each other, | 0:11:35 | 0:11:37 | |
but if there's life, it'll keep pumping it into the atmosphere | 0:11:37 | 0:11:40 | |
so you'll see more of it than you would expect. | 0:11:40 | 0:11:42 | |
The best thing is to find them together. | 0:11:42 | 0:11:44 | |
Now, these are signatures of simple life... | 0:11:44 | 0:11:48 | |
What about us? | 0:11:48 | 0:11:49 | |
What should we be looking for if we're looking for intelligent life? | 0:11:49 | 0:11:52 | |
Sadly, we'd be looking for pollutants. | 0:11:52 | 0:11:54 | |
So, we all hear about CFCs and the hole in the ozone layer. | 0:11:54 | 0:11:57 | |
They are really long lived and they also cannot be created naturally. | 0:11:57 | 0:12:01 | |
They are created by us and by intelligent life. | 0:12:01 | 0:12:04 | |
So, when we look at other atmospheres, | 0:12:04 | 0:12:06 | |
if we see CFCs in their atmospheres, | 0:12:06 | 0:12:08 | |
then we know there's some kind of a technological civilisation | 0:12:08 | 0:12:11 | |
-on that planet. -Just CFCs? | 0:12:11 | 0:12:12 | |
Wouldn't that just indicate that people are using deodorants on those planets? | 0:12:12 | 0:12:16 | |
If we see just CFCs, it might indicate that there was once | 0:12:16 | 0:12:19 | |
an advanced civilisation there that's created it. | 0:12:19 | 0:12:22 | |
What would be amazing to find would be oxygen as well as CFCs, | 0:12:22 | 0:12:26 | |
because that means there might be a civilisation there right now. | 0:12:26 | 0:12:29 | |
-That is using deodorants and fridges... -And hairspray... -..but still alive. -Yes | 0:12:29 | 0:12:34 | |
Well, good luck with the hunt. Thank you. | 0:12:34 | 0:12:36 | |
So, the good news is that we can detect signs of alien life | 0:12:43 | 0:12:46 | |
in the atmosphere of exoplanets. | 0:12:46 | 0:12:48 | |
But the bad news is that they're so far away - | 0:12:48 | 0:12:51 | |
how can we possibly pick up the signal? | 0:12:51 | 0:12:53 | |
Well, that's just what they specialise in | 0:12:53 | 0:12:55 | |
here at Exeter University. | 0:12:55 | 0:12:57 | |
Chris is talking to Hannah Wakeford who is part of that team. | 0:12:57 | 0:13:02 | |
So, most of the planets that we know about have been found | 0:13:02 | 0:13:04 | |
via the transit method. How does that work? | 0:13:04 | 0:13:07 | |
So, if you imagine that this is our star that we're looking at, | 0:13:07 | 0:13:10 | |
we're seeing the light from that star. | 0:13:10 | 0:13:13 | |
But if you put a planet in orbit around that, | 0:13:13 | 0:13:15 | |
as it passes in front of the star, | 0:13:15 | 0:13:17 | |
it's going to steadily block out that light, | 0:13:17 | 0:13:20 | |
so we're going to see a change in the amount of light we're observing, | 0:13:20 | 0:13:23 | |
and it's about a 1% change in the amount of light. | 0:13:23 | 0:13:26 | |
So, imagine a mosquito flying in front of a lamppost | 0:13:26 | 0:13:29 | |
1km to 1,000km away. | 0:13:29 | 0:13:32 | |
It's a very small change in the amount of light. | 0:13:32 | 0:13:35 | |
But as that planet passes in front, it's blocking it out, | 0:13:35 | 0:13:39 | |
so that allows us to detect these planets, and it also allows us | 0:13:39 | 0:13:43 | |
to see any starlight that's shining through the atmosphere. | 0:13:43 | 0:13:46 | |
The ones that we're looking at at the moment | 0:13:46 | 0:13:49 | |
are called hot Jupiters, and these are mostly gas giants, | 0:13:49 | 0:13:52 | |
so they have really big atmospheres. | 0:13:52 | 0:13:54 | |
That means that we're seeing a lot of the light shining through | 0:13:54 | 0:13:57 | |
that atmosphere, and we can tell you loads of things about them. | 0:13:57 | 0:14:00 | |
I think one way to understand what's going on there | 0:14:00 | 0:14:02 | |
is to think about what that would look like from the planet itself. | 0:14:02 | 0:14:05 | |
There's a couple of planets where we've got a synthetic sunset, | 0:14:05 | 0:14:09 | |
as such, from that planet. | 0:14:09 | 0:14:11 | |
This planet here - HD 189733b - | 0:14:11 | 0:14:14 | |
is an observation that looks very much like the Earth would, | 0:14:14 | 0:14:18 | |
and that's because the atmosphere of this planet | 0:14:18 | 0:14:20 | |
is scattering the blue light. | 0:14:20 | 0:14:21 | |
So, like the Earth's atmosphere scatters the blue light, | 0:14:21 | 0:14:24 | |
which is why you have a blue sky, which causes the red sunset, | 0:14:24 | 0:14:27 | |
you get the same thing. | 0:14:27 | 0:14:29 | |
And this is another one. This is HD 209458b. | 0:14:29 | 0:14:32 | |
You can see that it's a completely alien sunset, | 0:14:32 | 0:14:35 | |
and that's because there's sodium in the atmosphere of this planet. | 0:14:35 | 0:14:39 | |
We've detected sodium in the atmosphere | 0:14:39 | 0:14:41 | |
by the amount of light it blocks out at a certain wavelength. | 0:14:41 | 0:14:44 | |
It's not just sodium that we're trying to detect. | 0:14:44 | 0:14:46 | |
We're also trying to detect potassium | 0:14:46 | 0:14:48 | |
and water in the atmospheres of these planets. | 0:14:48 | 0:14:50 | |
What about the weather on these planets? | 0:14:50 | 0:14:52 | |
We talk about Jupiter and you think of the bands, and the clouds, | 0:14:52 | 0:14:54 | |
and the storms that are going on. | 0:14:54 | 0:14:57 | |
Do we know anything about these planets | 0:14:57 | 0:14:58 | |
-and whether they have similar weather? -Yeah. | 0:14:58 | 0:15:01 | |
From the transit, from the light shining through the atmosphere, | 0:15:01 | 0:15:04 | |
we can determine what kind of structure it's passing through. | 0:15:04 | 0:15:08 | |
So, if it's passing through a gas, | 0:15:08 | 0:15:10 | |
then the light will interact in a certain way, | 0:15:10 | 0:15:13 | |
but if there's a solid particle in the way, | 0:15:13 | 0:15:15 | |
if there's something solid blocking it, like a rain droplet, | 0:15:15 | 0:15:19 | |
then the light bounces through that solid droplet | 0:15:19 | 0:15:22 | |
in a different way and that allows us to detect | 0:15:22 | 0:15:25 | |
whether there are solid particles in that atmosphere. | 0:15:25 | 0:15:27 | |
So we've got to the point where these hot Jupiters are worlds | 0:15:27 | 0:15:30 | |
with cloud, wind, sodium and potassium in their atmosphere, | 0:15:30 | 0:15:34 | |
but what we really care about are terrestrial planets. | 0:15:34 | 0:15:37 | |
Is there any hope there of using these techniques to work out | 0:15:37 | 0:15:40 | |
what their atmospheres are like? | 0:15:40 | 0:15:42 | |
Yeah, and everything that we're learning at the moment, | 0:15:42 | 0:15:44 | |
every technique we're doing, has been developed | 0:15:44 | 0:15:46 | |
since the first observation of a transiting planet | 0:15:46 | 0:15:48 | |
in 2002 and it's going to be used to look at these smaller worlds. | 0:15:48 | 0:15:53 | |
That means, as soon as we get the technology, | 0:15:53 | 0:15:56 | |
we'll be able to tell you for certain that these techniques | 0:15:56 | 0:15:59 | |
are correct, they're working, | 0:15:59 | 0:16:01 | |
we've tested them on these massive planets and | 0:16:01 | 0:16:03 | |
we have an understanding of how they work, and that's really important. | 0:16:03 | 0:16:06 | |
So, we're still in the first stages, but it's definitely in our future. | 0:16:06 | 0:16:09 | |
We'll look forward to those results. | 0:16:09 | 0:16:11 | |
I hope we'll be back many times before then and you can update us. | 0:16:11 | 0:16:14 | |
-Thank you very much. -Thank you. | 0:16:14 | 0:16:15 | |
The reason there's been such a boom in exoplanet detection | 0:16:21 | 0:16:24 | |
over the last few years has mainly been down to one mission - | 0:16:24 | 0:16:28 | |
the Kepler space telescope. | 0:16:28 | 0:16:30 | |
It alone has detected 978 new planets so far. | 0:16:30 | 0:16:34 | |
Launched in 2009, it has been searching a star-rich patch of sky. | 0:16:36 | 0:16:42 | |
But in May 2013, the spacecraft broke down. | 0:16:42 | 0:16:46 | |
Two of its reaction wheels had failed. | 0:16:46 | 0:16:49 | |
These are the gyroscopes that are used to orientate the spacecraft. | 0:16:49 | 0:16:53 | |
Without them, it couldn't remained locked on its target. | 0:16:53 | 0:16:57 | |
But in the last few months, | 0:16:57 | 0:16:59 | |
the mission has received a new lease of life, | 0:16:59 | 0:17:01 | |
due to some ingenious lateral thinking. | 0:17:01 | 0:17:04 | |
The team worked out that they could use the force | 0:17:04 | 0:17:06 | |
exerted by sunlight hitting the spacecraft to stabilise it. | 0:17:06 | 0:17:10 | |
Light exerts a pressure on any object it falls on. | 0:17:11 | 0:17:14 | |
As photons hit a surface, | 0:17:16 | 0:17:18 | |
they transfer some of their momentum to it. | 0:17:18 | 0:17:21 | |
It's a tiny force, but in the frictionless, near vacuum of space, | 0:17:21 | 0:17:25 | |
it has an effect. | 0:17:25 | 0:17:27 | |
The Kepler scientists are using this to their advantage. | 0:17:27 | 0:17:30 | |
It just so happens that the spacecraft is symmetrical | 0:17:30 | 0:17:33 | |
from one angle. If the remaining reaction wheels | 0:17:33 | 0:17:36 | |
can keep the spacecraft at that angle, | 0:17:36 | 0:17:38 | |
then the solar pressure hitting the panels | 0:17:38 | 0:17:40 | |
will keep it in balance. | 0:17:40 | 0:17:42 | |
But for it work, they have to be extremely accurate. | 0:17:42 | 0:17:46 | |
The slightest misalignment would cause a spacecraft to spin | 0:17:46 | 0:17:49 | |
rather than stabilising it. | 0:17:49 | 0:17:51 | |
But early tests look promising, | 0:17:51 | 0:17:53 | |
and Kepler is once again looking for alien worlds. | 0:17:53 | 0:17:56 | |
Next up, Pete with his highlights of what to see | 0:18:03 | 0:18:06 | |
in this month's night sky. | 0:18:06 | 0:18:08 | |
But first, here are his tips for capturing | 0:18:09 | 0:18:12 | |
the full magnificence of one of the largest objects on view. | 0:18:12 | 0:18:16 | |
As we enter the autumn, the nights are getting longer and longer | 0:18:16 | 0:18:19 | |
and that means it's a perfect time to start doing some stargazing. | 0:18:19 | 0:18:23 | |
One of the best objects to look for at this time of year | 0:18:23 | 0:18:25 | |
is the Andromeda Galaxy. | 0:18:25 | 0:18:27 | |
Like our own galaxy, Andromeda is a spiral. | 0:18:28 | 0:18:31 | |
It's two and a half million light years away, | 0:18:33 | 0:18:35 | |
making it one of the furthest objects | 0:18:35 | 0:18:37 | |
it's possible to view with the naked eye. | 0:18:37 | 0:18:40 | |
Now, with a reasonably dark, moonless sky, | 0:18:41 | 0:18:43 | |
it should look like a faint, elongated smudge, | 0:18:43 | 0:18:46 | |
but when you look at Andromeda, | 0:18:46 | 0:18:48 | |
you may not be seeing the entire galaxy. | 0:18:48 | 0:18:50 | |
The central core stands out much more clearly | 0:18:52 | 0:18:54 | |
than the rest of the galaxy and is what many people see. | 0:18:54 | 0:18:58 | |
But some of the best views of Andromeda come from photographing it, | 0:19:00 | 0:19:04 | |
and depending on how you do it, its appearance can change dramatically. | 0:19:04 | 0:19:07 | |
You can see this for yourself by taking a series of pictures | 0:19:10 | 0:19:13 | |
and varying the exposures between each. | 0:19:13 | 0:19:16 | |
I'll start with a relativity short exposure length | 0:19:16 | 0:19:19 | |
of about 30 seconds or so. | 0:19:19 | 0:19:21 | |
What you see here is very similar to what you'd see with the naked eye. | 0:19:25 | 0:19:30 | |
That's just picked out the core of the galaxy there. | 0:19:30 | 0:19:33 | |
As we increase the exposure time, more details start to come out. | 0:19:35 | 0:19:40 | |
Past 60 seconds, the galaxy starts to take on a sharp edge, | 0:19:40 | 0:19:44 | |
which is the result of a dust lane blocking starlight. | 0:19:44 | 0:19:47 | |
As we up the exposure, | 0:19:49 | 0:19:50 | |
the Andromeda Galaxy gets bigger and bigger. | 0:19:50 | 0:19:54 | |
Now, in my earlier 30-second-exposure shot, | 0:19:56 | 0:19:59 | |
all I picked out, really, was the core of the galaxy. | 0:19:59 | 0:20:02 | |
Now, in this longer exposure, | 0:20:02 | 0:20:04 | |
I can actually see the beautiful spiral arms either side | 0:20:04 | 0:20:07 | |
of the core quite clearly, there. | 0:20:07 | 0:20:10 | |
However you view it, Andromeda is a magnificent sight, | 0:20:10 | 0:20:15 | |
and if you do capture its true size, | 0:20:15 | 0:20:17 | |
it appears six times the width of a full moon. | 0:20:17 | 0:20:20 | |
The Andromeda Galaxy is really easy to find in the night sky. | 0:20:22 | 0:20:27 | |
Here's my guide to finding it and other highlights this month. | 0:20:27 | 0:20:31 | |
A quick way to locate the Andromeda Galaxy, | 0:20:32 | 0:20:35 | |
which is in the constellation of the same name, | 0:20:35 | 0:20:37 | |
is to first identify the W-shaped pattern of Cassiopeia. | 0:20:37 | 0:20:41 | |
The right half of the W is like an arrow, | 0:20:43 | 0:20:46 | |
pointing down towards the star Mirach in the constellation of Andromeda. | 0:20:46 | 0:20:50 | |
Look up slightly from Mirach to locate the fainter Mu Andromedae, | 0:20:52 | 0:20:57 | |
and a little further up still | 0:20:57 | 0:20:59 | |
to find the even fainter star Nu Andromedae. | 0:20:59 | 0:21:03 | |
The Andromeda Galaxy sits slightly above and slightly right of Nu. | 0:21:04 | 0:21:08 | |
Also this month, just before sunrise on the 20th, | 0:21:10 | 0:21:13 | |
you'll be greeted by the magnificent sight of Jupiter | 0:21:13 | 0:21:16 | |
next to a thin, waning crescent moon in the eastern part of the sky. | 0:21:16 | 0:21:20 | |
Finally, on the 28th, | 0:21:24 | 0:21:26 | |
look low down in the southwest about an hour after sunset | 0:21:26 | 0:21:29 | |
to see planet Mars | 0:21:29 | 0:21:31 | |
close to the similar-brightness star Antares in Scorpius. | 0:21:31 | 0:21:34 | |
The name Antares literally means "the rival of Mars" | 0:21:36 | 0:21:39 | |
because it's supposed to look just like the red planet. | 0:21:39 | 0:21:43 | |
Now's your chance to check whether it really deserves that title. | 0:21:43 | 0:21:46 | |
Now back to the hunt for ET. | 0:21:50 | 0:21:52 | |
So, we've talked about what life is and where it can exist, | 0:21:53 | 0:21:56 | |
but what are the odds of us actually finding life out in the cosmos? | 0:21:56 | 0:22:00 | |
53 years ago, astrobiologist Frank Drake | 0:22:00 | 0:22:03 | |
penned his famous equation | 0:22:03 | 0:22:05 | |
which aimed at answering precisely this question, | 0:22:05 | 0:22:08 | |
but we know much more about the universe now than we did then, | 0:22:08 | 0:22:11 | |
and Maggie has been catching up with astrobioligist | 0:22:11 | 0:22:14 | |
and alien hunter Duncan Forgan to find out how far we've got. | 0:22:14 | 0:22:17 | |
The Drake equation is made up of a series of conditions | 0:22:20 | 0:22:23 | |
that need to be met for us to communicate with alien life. | 0:22:23 | 0:22:27 | |
Each letter represents one of these factors, | 0:22:27 | 0:22:30 | |
such as how many stars have planets orbiting them? | 0:22:30 | 0:22:33 | |
Or how many of these planets support life? | 0:22:33 | 0:22:35 | |
Duncan is going to help me | 0:22:35 | 0:22:37 | |
fill in these figures based on the latest research. | 0:22:37 | 0:22:39 | |
When we start populating this, how does that work? | 0:22:40 | 0:22:43 | |
Well, it gets a bit tricky to populate. | 0:22:43 | 0:22:45 | |
When we start on the left-hand side, | 0:22:45 | 0:22:47 | |
we're actually in the bits that we know quite well, | 0:22:47 | 0:22:50 | |
and as we go across the terms, we get closer to the edge | 0:22:50 | 0:22:53 | |
of our current understanding, and then we go past it into the unknown. | 0:22:53 | 0:22:56 | |
OK, let's start at the beginning. Start with R. | 0:22:56 | 0:22:58 | |
The rate of star formation in our galaxy. | 0:22:58 | 0:23:01 | |
So the rate of star formation in our galaxy, | 0:23:01 | 0:23:03 | |
the number we expect to see per year | 0:23:03 | 0:23:04 | |
is somewhere between five and seven. | 0:23:04 | 0:23:06 | |
So, why don't we start with just five? Five per year. | 0:23:06 | 0:23:08 | |
-That's a nice, round number. -And conservative. -Conservative. | 0:23:08 | 0:23:12 | |
So, fg - the number of stars that have a planet. | 0:23:12 | 0:23:14 | |
That number has changed a lot, obviously, because we now | 0:23:14 | 0:23:17 | |
know a lot about exoplanets that we didn't know 20 years ago. | 0:23:17 | 0:23:20 | |
We think now that this particular f term is, in fact, one. | 0:23:20 | 0:23:24 | |
So we're not assuming that all stars in the galaxy have planets, | 0:23:24 | 0:23:27 | |
but many stars have multiple planets, so that keeps that at one. | 0:23:27 | 0:23:30 | |
-Yes. -And that recent finding is from what we're doing with | 0:23:30 | 0:23:33 | |
the exoplanets at the moment. | 0:23:33 | 0:23:34 | |
Yes. This is cutting edge research right here. | 0:23:34 | 0:23:37 | |
The next two terms relate to the number of those planets | 0:23:37 | 0:23:39 | |
that can support life, that are habitable. | 0:23:39 | 0:23:43 | |
So we're moving on to fp. | 0:23:43 | 0:23:44 | |
fp is where it starts to get a bit trickier for us | 0:23:44 | 0:23:47 | |
because now we have to start thinking about | 0:23:47 | 0:23:50 | |
-what the word habitable means... -Oh. | 0:23:50 | 0:23:52 | |
We don't have a good, strict definition of what life is, so that | 0:23:52 | 0:23:56 | |
actually hampers our ability to then say, "What does life like?" | 0:23:56 | 0:23:59 | |
-Yeah. -So if you want to put the frontier of science at this point, | 0:23:59 | 0:24:04 | |
then it kind of exists here in this line. | 0:24:04 | 0:24:07 | |
So we're now at this point where we've pushed our knowledge | 0:24:07 | 0:24:11 | |
of the terms in Drake's equation all the way to here. | 0:24:11 | 0:24:13 | |
I suppose, when Drake started, we were back here. | 0:24:13 | 0:24:16 | |
Yeah, so Drake wrote this equation in 1961 | 0:24:16 | 0:24:18 | |
and he only had one term, but we've managed to push these things | 0:24:18 | 0:24:21 | |
and, really, just in the last couple of years. | 0:24:21 | 0:24:24 | |
In the last decade, we've really gone from... | 0:24:24 | 0:24:27 | |
We were kind of here with the first detection of exoplanets | 0:24:27 | 0:24:29 | |
about 20 years ago, and with the Kepler space telescope | 0:24:29 | 0:24:32 | |
and other missions like it, we're really pushing | 0:24:32 | 0:24:35 | |
in this direction now and we're picking up a bit of speed. | 0:24:35 | 0:24:38 | |
But from here on in, it really does become guesswork. | 0:24:38 | 0:24:42 | |
There's how frequently does life form? | 0:24:42 | 0:24:45 | |
And the likelihood of that life being intelligent? | 0:24:46 | 0:24:49 | |
But what do we mean by intelligence? | 0:24:49 | 0:24:51 | |
There are many definitions of intelligence, | 0:24:51 | 0:24:54 | |
and in this very strict definition of the sense, | 0:24:54 | 0:24:56 | |
really, we became intelligent | 0:24:56 | 0:24:58 | |
when we started sending strong radio signals out into space. | 0:24:58 | 0:25:01 | |
And that was really only about 100 years ago. | 0:25:01 | 0:25:03 | |
So we've not been "intelligent", quote, unquote, for very long. | 0:25:03 | 0:25:07 | |
And the last term, L. | 0:25:07 | 0:25:08 | |
The last term, L, is how long do we expect to see that signal? | 0:25:08 | 0:25:11 | |
And what that really means is | 0:25:11 | 0:25:13 | |
how long do we expect the civilisation to last? | 0:25:13 | 0:25:15 | |
So you need to get that overlap of intelligence | 0:25:15 | 0:25:17 | |
to actually make that communication. | 0:25:17 | 0:25:19 | |
That's a very good point, and it kind of demonstrates | 0:25:19 | 0:25:21 | |
that the galaxy is big in space, but it's also big in time. | 0:25:21 | 0:25:24 | |
There's lots of time in the galaxy, so you've got to make sure that, | 0:25:24 | 0:25:28 | |
if you want two civilisations to have a conversation, | 0:25:28 | 0:25:30 | |
they have to be close in space and close in time at the same time. | 0:25:30 | 0:25:33 | |
Duncan's speculates that the average civilisation | 0:25:33 | 0:25:36 | |
will be able to communicate for 1,000 years. | 0:25:36 | 0:25:39 | |
So what's the answer to the equation? | 0:25:39 | 0:25:42 | |
It's about five. | 0:25:42 | 0:25:44 | |
Five? But that's in the whole of the galaxy? | 0:25:44 | 0:25:47 | |
No, that's at any one instant, if we looked up into the night sky, | 0:25:47 | 0:25:50 | |
we'd expect to see five, and that includes us as well, | 0:25:50 | 0:25:53 | |
-so we'd actually expect to see four. -THEY LAUGH | 0:25:53 | 0:25:56 | |
I think that, fundamentally, it's a question we really want | 0:25:56 | 0:25:58 | |
to answer and it's something that people have always wanted to answer. | 0:25:58 | 0:26:02 | |
I think, for me, that's the beauty of this equation. | 0:26:02 | 0:26:04 | |
In some way, it kind of encapsulates | 0:26:04 | 0:26:06 | |
all of mankind's search to understand itself | 0:26:06 | 0:26:09 | |
as well as understanding its place in the universe. | 0:26:09 | 0:26:12 | |
So, you start with the terms that are to do with astronomy, | 0:26:12 | 0:26:15 | |
physics, chemistry, | 0:26:15 | 0:26:17 | |
and then you get onto the planetary sciences and the geology, | 0:26:17 | 0:26:19 | |
and then you have the biology, | 0:26:19 | 0:26:21 | |
and then as you get to the very end, you have to start thinking | 0:26:21 | 0:26:24 | |
about the things that aren't the "hard" sciences, | 0:26:24 | 0:26:26 | |
-but the social sciences. -Yes. | 0:26:26 | 0:26:28 | |
You have to think about the psychology of life, | 0:26:28 | 0:26:30 | |
you have to think about anthropology. | 0:26:30 | 0:26:32 | |
The whole academic discipline of mankind is somehow | 0:26:32 | 0:26:34 | |
encapsulated in these eight letters. | 0:26:34 | 0:26:36 | |
-But I've never seen it in that way, so thank you very much. -Thank you. | 0:26:36 | 0:26:39 | |
-A new perspective on the Drake equation. -Thank you. | 0:26:39 | 0:26:42 | |
That's about it for this month, | 0:26:46 | 0:26:47 | |
but we wanted to let you know about a fabulous competition | 0:26:47 | 0:26:50 | |
being run by Blue Peter to design the official mission patch for our | 0:26:50 | 0:26:54 | |
British astronaut Tim Peake's visit to the International Space Station. | 0:26:54 | 0:26:58 | |
You need to be between the ages of six to 15 to enter. | 0:26:58 | 0:27:01 | |
If you want more details of the competition, | 0:27:01 | 0:27:03 | |
and the terms and conditions, please go to our website. | 0:27:03 | 0:27:06 | |
The competition closes midday on 26th September, | 0:27:06 | 0:27:08 | |
so do get your designs in. | 0:27:08 | 0:27:11 | |
We can't leave you without mentioning Rosetta, | 0:27:11 | 0:27:13 | |
ESA's comet chasing probe, | 0:27:13 | 0:27:14 | |
now just 50km from Churyumov-Gerasimenko | 0:27:14 | 0:27:18 | |
and getting ready for the touchdown of the Philae lander | 0:27:18 | 0:27:21 | |
in just a few months' time. | 0:27:21 | 0:27:23 | |
ESA have already identified five potential landing sites, | 0:27:23 | 0:27:26 | |
which you can see up here, | 0:27:26 | 0:27:28 | |
and they'll narrow that down to two in the next few weeks, | 0:27:28 | 0:27:30 | |
but my favourite landing site is definitely J, | 0:27:30 | 0:27:33 | |
because it's accessible. And they've just been travelling for so long. | 0:27:33 | 0:27:36 | |
-I just want it to all go right, so go for the easy picking. -I think that's an engineer's view. | 0:27:36 | 0:27:40 | |
As a scientist, I'm a big fan of what they're calling site A, | 0:27:40 | 0:27:42 | |
which is on the larger lobe of the comet, | 0:27:42 | 0:27:44 | |
the body of the rubber duck, if you think of the thing as a rubber duck. | 0:27:44 | 0:27:47 | |
Land there and you get a view of both parts of the comet, | 0:27:47 | 0:27:50 | |
and I think that would be really exciting. | 0:27:50 | 0:27:52 | |
Good, but go for the easy pickings. | 0:27:52 | 0:27:54 | |
But we'll be finding out exactly what they choose in the next few weeks. | 0:27:54 | 0:27:57 | |
When we come back next month, we'll be talking about | 0:27:57 | 0:27:59 | |
the outer edges of the solar system, its ice giants, Uranus and Neptune. | 0:27:59 | 0:28:03 | |
-In the meantime, get outside and get looking up. -Good night. | 0:28:03 | 0:28:07 |