0:00:02 > 0:00:04When we look up at the cosmos,
0:00:04 > 0:00:08we see a universe that's filled with billions and billons of galaxies,
0:00:08 > 0:00:12each of them home to billions and billions of stars
0:00:12 > 0:00:14shining back down upon us.
0:00:16 > 0:00:18But despite the vastness...
0:00:18 > 0:00:20from here, it looks a lonely place.
0:00:22 > 0:00:25Are we the only life that looks up at the sky at night?
0:00:25 > 0:00:29Or somewhere else, around some other twinkling star,
0:00:29 > 0:00:32are there other beings doing the same?
0:00:34 > 0:00:38Remarkably, we're making progress towards answering that question.
0:00:38 > 0:00:40In the last few years, we've discovered our galaxy
0:00:40 > 0:00:42is teeming with planets,
0:00:42 > 0:00:45alien worlds in almost unimaginable variety.
0:00:45 > 0:00:46And for the first time,
0:00:46 > 0:00:49we're actually getting a glimpse of what these worlds are really like.
0:00:49 > 0:00:52But the question is, can any of them harbour life?
0:00:52 > 0:00:55Come with us on a journey through the galaxy
0:00:55 > 0:00:56as we hunt for ET.
0:00:56 > 0:00:58Welcome to The Sky At Night.
0:01:24 > 0:01:27Our search for alien life doesn't have to be limited
0:01:27 > 0:01:30to waiting for extraterrestrials to give us a call,
0:01:30 > 0:01:33new astronomical techniques have enabled amazing discoveries,
0:01:33 > 0:01:37taking us closer to finding life out there than we've ever been.
0:01:37 > 0:01:40Some of the most advanced work in studying alien atmospheres
0:01:40 > 0:01:42is done here at Exeter University.
0:01:42 > 0:01:45In this programme, we're going to be pushing at the boundaries of science
0:01:45 > 0:01:47in the search for alien life.
0:01:47 > 0:01:50Coming up, how do we define life
0:01:50 > 0:01:52and would we recognise it if we saw it?
0:01:52 > 0:01:54Adam Rutherford investigates.
0:01:56 > 0:01:58So, when we look at other atmospheres,
0:01:58 > 0:02:01if we see CFCs in their atmospheres, then we know
0:02:01 > 0:02:03there's some kind of a technological civilisation on that planet.
0:02:03 > 0:02:08These are sunsets, seen from other planets,
0:02:08 > 0:02:11orbiting distant stars.
0:02:11 > 0:02:12What can they tell us
0:02:12 > 0:02:15about the potential for extraterrestrial life?
0:02:17 > 0:02:21And how many alien civilisations could there be out there?
0:02:21 > 0:02:23If we looked up into the night sky,
0:02:23 > 0:02:25we'd expect to see five, and that includes us,
0:02:25 > 0:02:27so we'd actually expect to see four.
0:02:29 > 0:02:30Plus, as autumn comes upon us,
0:02:30 > 0:02:35Pete is looking at one of the great spectacles of the night sky -
0:02:35 > 0:02:37Andromeda.
0:02:41 > 0:02:43If we want to discover life beyond our solar system,
0:02:43 > 0:02:45there are certain things we should look for,
0:02:45 > 0:02:47and the first is a planet -
0:02:47 > 0:02:50preferably one rather like the Earth, with liquid water,
0:02:50 > 0:02:52continents and a nice atmosphere.
0:02:52 > 0:02:55And this hunt for extrasolar planets, or exoplanets,
0:02:55 > 0:02:57is beginning to pay off.
0:02:58 > 0:03:01Until 1995, despite decades of searching,
0:03:01 > 0:03:05our solar system was the only one that we knew about.
0:03:07 > 0:03:09Then, suddenly, everything changed
0:03:09 > 0:03:11when two astronomers in Geneva
0:03:11 > 0:03:13announced the discovery of this planet.
0:03:13 > 0:03:17Rapidly orbiting, and weighing about half the mass of Jupiter,
0:03:17 > 0:03:21It goes round the star 51 Pegasi, just 50 light years from Earth.
0:03:23 > 0:03:25But since then, the discoveries have come thick and fast
0:03:25 > 0:03:28and we've found all sorts of unexpected planets.
0:03:29 > 0:03:35Then there's HD 209458b, a planet larger than Jupiter,
0:03:35 > 0:03:39which is so close to its parent star that it's losing its atmosphere.
0:03:39 > 0:03:43More than 10,000 tonnes a second of hydrogen is swept off
0:03:43 > 0:03:47in a long train, rather like a comet's tail.
0:03:47 > 0:03:50And just over 150 light years from Earth,
0:03:50 > 0:03:53there's a planet in a system with three suns,
0:03:53 > 0:03:57creating this astonishing sight from a hypothetical moon.
0:03:57 > 0:04:00But none of these exotic worlds could support life.
0:04:00 > 0:04:03What we need is a planet in the Goldilocks zone.
0:04:03 > 0:04:06Not too hot and not too cold, but just right.
0:04:06 > 0:04:08Able to support liquid water
0:04:08 > 0:04:10and therefore maybe life on its surface.
0:04:10 > 0:04:15We have found a number of planets that should be rocky.
0:04:15 > 0:04:18But the candidate that's closest to our own Earth is this one,
0:04:18 > 0:04:21Kepler 186f.
0:04:21 > 0:04:23It was discovered in April this year
0:04:23 > 0:04:26and is the first planet we've found that's close in size to Earth
0:04:26 > 0:04:30and that's the right distance from its sun to maybe harbour life.
0:04:33 > 0:04:38In total, we've now discovered 1,516 exoplanets,
0:04:38 > 0:04:40nearly half of them in the past year,
0:04:40 > 0:04:42and the hunt continues.
0:04:44 > 0:04:46So, we can find alien worlds,
0:04:46 > 0:04:48but what about the aliens themselves?
0:04:48 > 0:04:51Do any of these planets harbour life?
0:04:51 > 0:04:53It's a tantalizing question,
0:04:53 > 0:04:57and I wonder, even if we found life, would we recognise it?
0:04:57 > 0:04:59Adam Rutherford is investigating.
0:05:05 > 0:05:09Everywhere you look on our planet, there is life,
0:05:09 > 0:05:13and it comes in all shapes and sizes.
0:05:13 > 0:05:17From the tiniest bacteria, to the blue whale,
0:05:17 > 0:05:21to the fungi that spreads over hundreds of acres,
0:05:21 > 0:05:25there seems to be an almost endless variety to life on Earth.
0:05:25 > 0:05:30And this astonishing variety raises a really interesting question...
0:05:30 > 0:05:33how do we actually define life?
0:05:35 > 0:05:38This is a question we really have to answer
0:05:38 > 0:05:40if we want to look for life off-world.
0:05:42 > 0:05:45We instinctively understand what life is,
0:05:45 > 0:05:47we know it when we see it.
0:05:47 > 0:05:50The tree is alive but the clouds above are not.
0:05:53 > 0:05:56But codifying these differences isn't easy.
0:05:56 > 0:06:00What's needed are a series of testable criteria
0:06:00 > 0:06:04that fit all living things and exclude all non-living things.
0:06:06 > 0:06:08One way is to look at how life behaves.
0:06:11 > 0:06:14There are certain behaviours that all life seems to display,
0:06:14 > 0:06:18such as movement, growth, respiration,
0:06:18 > 0:06:21and, in particular, reproduction.
0:06:21 > 0:06:26But these characteristics might not always be exclusive to life.
0:06:30 > 0:06:31Take a flame, for example.
0:06:31 > 0:06:33It starts with a spark.
0:06:36 > 0:06:39And as the flame gets bigger and bigger, it consumes fuel
0:06:39 > 0:06:43in the form of oxygen from the air and carbon from the wick.
0:06:43 > 0:06:45If you blow on it...
0:06:45 > 0:06:50it responds and it produces wastes in the form of smoke and gas.
0:06:50 > 0:06:52Now, these are all the types of things that we associate
0:06:52 > 0:06:54with living organisms,
0:06:54 > 0:06:57and it also does something which is a lot like reproducing.
0:06:57 > 0:07:00You can use one flame...
0:07:00 > 0:07:02to create another...
0:07:02 > 0:07:04and another...
0:07:05 > 0:07:07..and another...
0:07:07 > 0:07:09and so on.
0:07:10 > 0:07:12So, the question is...
0:07:12 > 0:07:14is a flame alive?
0:07:16 > 0:07:19Of course, the answer to this is no.
0:07:19 > 0:07:23One of the reasons is that the flame doesn't contain any information,
0:07:23 > 0:07:28and information seems to be a key characteristic of life.
0:07:28 > 0:07:32All life reproduces itself, and when it does so, it passes on information
0:07:32 > 0:07:35from generation to generation.
0:07:35 > 0:07:38Now, that information is encoded in DNA.
0:07:38 > 0:07:42Every time a cell divides, it passes it on from cell to cell,
0:07:42 > 0:07:44from parent to offspring.
0:07:46 > 0:07:50But does the presence of DNA define what life is
0:07:50 > 0:07:52everywhere in the universe?
0:07:55 > 0:07:58Well, for me, the answer is no.
0:07:58 > 0:08:03Yes, DNA is universal amongst all living things on Earth,
0:08:03 > 0:08:08but it doesn't help us to understand how life began in the first place.
0:08:08 > 0:08:12It misses a key process that makes living things 'alive'.
0:08:12 > 0:08:14DNA replication requires energy,
0:08:14 > 0:08:17and when we look at how cells generate that energy,
0:08:17 > 0:08:21it is a more fundamental process than replication.
0:08:22 > 0:08:26Whilst DNA is how life replicates here on Earth,
0:08:26 > 0:08:29it might not be the case elsewhere.
0:08:29 > 0:08:32But there is a process that should be universal.
0:08:35 > 0:08:39Life is a chemical reaction, a process of extracting energy
0:08:39 > 0:08:43from the environment and using it to sustain itself -
0:08:43 > 0:08:46a process we call metabolism -
0:08:46 > 0:08:49and this is the key to defining life.
0:08:52 > 0:08:54You can see it in action here in the lab.
0:08:57 > 0:09:00In this jar is some water and a plant called egeria.
0:09:00 > 0:09:04Now, the plant consumes energy in the form of light
0:09:04 > 0:09:07and uses it in the production of glucose.
0:09:07 > 0:09:10Now, as a by-product of that metabolic process,
0:09:10 > 0:09:13it produces oxygen, and, if we look very closely,
0:09:13 > 0:09:16we should be able to see tiny bubbles of oxygen
0:09:16 > 0:09:17coming off the plant.
0:09:17 > 0:09:19There you go.
0:09:19 > 0:09:21Now, this is a process that all plants do.
0:09:21 > 0:09:23It's called photosynthesis.
0:09:23 > 0:09:26They extract energy from the environment to create something new -
0:09:26 > 0:09:31in this case, using light to convert carbon dioxide and water
0:09:31 > 0:09:34into sugars, and then the plant uses that sugar
0:09:34 > 0:09:37to power complex living processes.
0:09:38 > 0:09:42Without metabolism, there would be no energy to sustain life,
0:09:42 > 0:09:45and no energy to reproduce.
0:09:45 > 0:09:49And luckily, metabolism leaves a trail of evidence behind it.
0:09:49 > 0:09:54In fact, the oxygen that fills our atmosphere was created by life.
0:09:55 > 0:09:59So, forget about radio signals from ET.
0:09:59 > 0:10:01If we really want to find signs of life,
0:10:01 > 0:10:04we should be looking at the atmospheres of exoplanets.
0:10:04 > 0:10:08And it's possible to do this by analysing light that passes through
0:10:08 > 0:10:13the atmospheres of distant planets to reveal what they are made of.
0:10:13 > 0:10:16To understand what signs we should look out for,
0:10:16 > 0:10:17I'm meeting Louisa Preston.
0:10:18 > 0:10:21If we were to look at the Earth from space,
0:10:21 > 0:10:24would we be able to tell that there is life on Earth?
0:10:24 > 0:10:29Yes, we would be able to see oxygen, methane, carbon dioxide...
0:10:29 > 0:10:32We also can look at the Earth whilst we're standing on it.
0:10:32 > 0:10:34The sunlight hits the atmosphere of the Earth,
0:10:34 > 0:10:36and it gets reflected away,
0:10:36 > 0:10:39and it hits the moon and then the moon reflects it back to us,
0:10:39 > 0:10:41so we can observe ourselves. It's called earthshine.
0:10:41 > 0:10:45So, we look at the moon and we can tell that there's life on Earth?
0:10:45 > 0:10:46Yes!
0:10:46 > 0:10:49How do we then transfer that into looking for life
0:10:49 > 0:10:51in exoplanets, in other planets?
0:10:51 > 0:10:54Well, because we know that the atmosphere
0:10:54 > 0:10:57can harbour these different types of molecules that life creates,
0:10:57 > 0:11:00we can look for exactly the same thing when we look at exoplanets,
0:11:00 > 0:11:03but we just have to figure out what the exact right molecules are.
0:11:03 > 0:11:06So, oxygen is definitely a by-signature that we would look for
0:11:06 > 0:11:07on another planet.
0:11:07 > 0:11:10The problem is, it can be made from non-biological ways,
0:11:10 > 0:11:12same with methane,
0:11:12 > 0:11:14so we have to be careful of these false positives, as we call them.
0:11:14 > 0:11:17So, is it that we're looking for a particular combination
0:11:17 > 0:11:19of those gases in the atmosphere?
0:11:19 > 0:11:22The right amount of methane, the right amount of oxygen...
0:11:22 > 0:11:25Sure. It's not the right amount, exactly.
0:11:25 > 0:11:27It's more a disequilibrium idea.
0:11:27 > 0:11:30There could be a bit of oxygen, there could be a bit of methane,
0:11:30 > 0:11:33but we want to see an excessive amount, because oxygen and methane
0:11:33 > 0:11:35are very short lived. They can degrade very quickly,
0:11:35 > 0:11:37react with other products, react with each other,
0:11:37 > 0:11:40but if there's life, it'll keep pumping it into the atmosphere
0:11:40 > 0:11:42so you'll see more of it than you would expect.
0:11:42 > 0:11:44The best thing is to find them together.
0:11:44 > 0:11:48Now, these are signatures of simple life...
0:11:48 > 0:11:49What about us?
0:11:49 > 0:11:52What should we be looking for if we're looking for intelligent life?
0:11:52 > 0:11:54Sadly, we'd be looking for pollutants.
0:11:54 > 0:11:57So, we all hear about CFCs and the hole in the ozone layer.
0:11:57 > 0:12:01They are really long lived and they also cannot be created naturally.
0:12:01 > 0:12:04They are created by us and by intelligent life.
0:12:04 > 0:12:06So, when we look at other atmospheres,
0:12:06 > 0:12:08if we see CFCs in their atmospheres,
0:12:08 > 0:12:11then we know there's some kind of a technological civilisation
0:12:11 > 0:12:12- on that planet.- Just CFCs?
0:12:12 > 0:12:16Wouldn't that just indicate that people are using deodorants on those planets?
0:12:16 > 0:12:19If we see just CFCs, it might indicate that there was once
0:12:19 > 0:12:22an advanced civilisation there that's created it.
0:12:22 > 0:12:26What would be amazing to find would be oxygen as well as CFCs,
0:12:26 > 0:12:29because that means there might be a civilisation there right now.
0:12:29 > 0:12:34- That is using deodorants and fridges...- And hairspray... - ..but still alive.- Yes
0:12:34 > 0:12:36Well, good luck with the hunt. Thank you.
0:12:43 > 0:12:46So, the good news is that we can detect signs of alien life
0:12:46 > 0:12:48in the atmosphere of exoplanets.
0:12:48 > 0:12:51But the bad news is that they're so far away -
0:12:51 > 0:12:53how can we possibly pick up the signal?
0:12:53 > 0:12:55Well, that's just what they specialise in
0:12:55 > 0:12:57here at Exeter University.
0:12:57 > 0:13:02Chris is talking to Hannah Wakeford who is part of that team.
0:13:02 > 0:13:04So, most of the planets that we know about have been found
0:13:04 > 0:13:07via the transit method. How does that work?
0:13:07 > 0:13:10So, if you imagine that this is our star that we're looking at,
0:13:10 > 0:13:13we're seeing the light from that star.
0:13:13 > 0:13:15But if you put a planet in orbit around that,
0:13:15 > 0:13:17as it passes in front of the star,
0:13:17 > 0:13:20it's going to steadily block out that light,
0:13:20 > 0:13:23so we're going to see a change in the amount of light we're observing,
0:13:23 > 0:13:26and it's about a 1% change in the amount of light.
0:13:26 > 0:13:29So, imagine a mosquito flying in front of a lamppost
0:13:29 > 0:13:321km to 1,000km away.
0:13:32 > 0:13:35It's a very small change in the amount of light.
0:13:35 > 0:13:39But as that planet passes in front, it's blocking it out,
0:13:39 > 0:13:43so that allows us to detect these planets, and it also allows us
0:13:43 > 0:13:46to see any starlight that's shining through the atmosphere.
0:13:46 > 0:13:49The ones that we're looking at at the moment
0:13:49 > 0:13:52are called hot Jupiters, and these are mostly gas giants,
0:13:52 > 0:13:54so they have really big atmospheres.
0:13:54 > 0:13:57That means that we're seeing a lot of the light shining through
0:13:57 > 0:14:00that atmosphere, and we can tell you loads of things about them.
0:14:00 > 0:14:02I think one way to understand what's going on there
0:14:02 > 0:14:05is to think about what that would look like from the planet itself.
0:14:05 > 0:14:09There's a couple of planets where we've got a synthetic sunset,
0:14:09 > 0:14:11as such, from that planet.
0:14:11 > 0:14:14This planet here - HD 189733b -
0:14:14 > 0:14:18is an observation that looks very much like the Earth would,
0:14:18 > 0:14:20and that's because the atmosphere of this planet
0:14:20 > 0:14:21is scattering the blue light.
0:14:21 > 0:14:24So, like the Earth's atmosphere scatters the blue light,
0:14:24 > 0:14:27which is why you have a blue sky, which causes the red sunset,
0:14:27 > 0:14:29you get the same thing.
0:14:29 > 0:14:32And this is another one. This is HD 209458b.
0:14:32 > 0:14:35You can see that it's a completely alien sunset,
0:14:35 > 0:14:39and that's because there's sodium in the atmosphere of this planet.
0:14:39 > 0:14:41We've detected sodium in the atmosphere
0:14:41 > 0:14:44by the amount of light it blocks out at a certain wavelength.
0:14:44 > 0:14:46It's not just sodium that we're trying to detect.
0:14:46 > 0:14:48We're also trying to detect potassium
0:14:48 > 0:14:50and water in the atmospheres of these planets.
0:14:50 > 0:14:52What about the weather on these planets?
0:14:52 > 0:14:54We talk about Jupiter and you think of the bands, and the clouds,
0:14:54 > 0:14:57and the storms that are going on.
0:14:57 > 0:14:58Do we know anything about these planets
0:14:58 > 0:15:01- and whether they have similar weather?- Yeah.
0:15:01 > 0:15:04From the transit, from the light shining through the atmosphere,
0:15:04 > 0:15:08we can determine what kind of structure it's passing through.
0:15:08 > 0:15:10So, if it's passing through a gas,
0:15:10 > 0:15:13then the light will interact in a certain way,
0:15:13 > 0:15:15but if there's a solid particle in the way,
0:15:15 > 0:15:19if there's something solid blocking it, like a rain droplet,
0:15:19 > 0:15:22then the light bounces through that solid droplet
0:15:22 > 0:15:25in a different way and that allows us to detect
0:15:25 > 0:15:27whether there are solid particles in that atmosphere.
0:15:27 > 0:15:30So we've got to the point where these hot Jupiters are worlds
0:15:30 > 0:15:34with cloud, wind, sodium and potassium in their atmosphere,
0:15:34 > 0:15:37but what we really care about are terrestrial planets.
0:15:37 > 0:15:40Is there any hope there of using these techniques to work out
0:15:40 > 0:15:42what their atmospheres are like?
0:15:42 > 0:15:44Yeah, and everything that we're learning at the moment,
0:15:44 > 0:15:46every technique we're doing, has been developed
0:15:46 > 0:15:48since the first observation of a transiting planet
0:15:48 > 0:15:53in 2002 and it's going to be used to look at these smaller worlds.
0:15:53 > 0:15:56That means, as soon as we get the technology,
0:15:56 > 0:15:59we'll be able to tell you for certain that these techniques
0:15:59 > 0:16:01are correct, they're working,
0:16:01 > 0:16:03we've tested them on these massive planets and
0:16:03 > 0:16:06we have an understanding of how they work, and that's really important.
0:16:06 > 0:16:09So, we're still in the first stages, but it's definitely in our future.
0:16:09 > 0:16:11We'll look forward to those results.
0:16:11 > 0:16:14I hope we'll be back many times before then and you can update us.
0:16:14 > 0:16:15- Thank you very much.- Thank you.
0:16:21 > 0:16:24The reason there's been such a boom in exoplanet detection
0:16:24 > 0:16:28over the last few years has mainly been down to one mission -
0:16:28 > 0:16:30the Kepler space telescope.
0:16:30 > 0:16:34It alone has detected 978 new planets so far.
0:16:36 > 0:16:42Launched in 2009, it has been searching a star-rich patch of sky.
0:16:42 > 0:16:46But in May 2013, the spacecraft broke down.
0:16:46 > 0:16:49Two of its reaction wheels had failed.
0:16:49 > 0:16:53These are the gyroscopes that are used to orientate the spacecraft.
0:16:53 > 0:16:57Without them, it couldn't remained locked on its target.
0:16:57 > 0:16:59But in the last few months,
0:16:59 > 0:17:01the mission has received a new lease of life,
0:17:01 > 0:17:04due to some ingenious lateral thinking.
0:17:04 > 0:17:06The team worked out that they could use the force
0:17:06 > 0:17:10exerted by sunlight hitting the spacecraft to stabilise it.
0:17:11 > 0:17:14Light exerts a pressure on any object it falls on.
0:17:16 > 0:17:18As photons hit a surface,
0:17:18 > 0:17:21they transfer some of their momentum to it.
0:17:21 > 0:17:25It's a tiny force, but in the frictionless, near vacuum of space,
0:17:25 > 0:17:27it has an effect.
0:17:27 > 0:17:30The Kepler scientists are using this to their advantage.
0:17:30 > 0:17:33It just so happens that the spacecraft is symmetrical
0:17:33 > 0:17:36from one angle. If the remaining reaction wheels
0:17:36 > 0:17:38can keep the spacecraft at that angle,
0:17:38 > 0:17:40then the solar pressure hitting the panels
0:17:40 > 0:17:42will keep it in balance.
0:17:42 > 0:17:46But for it work, they have to be extremely accurate.
0:17:46 > 0:17:49The slightest misalignment would cause a spacecraft to spin
0:17:49 > 0:17:51rather than stabilising it.
0:17:51 > 0:17:53But early tests look promising,
0:17:53 > 0:17:56and Kepler is once again looking for alien worlds.
0:18:03 > 0:18:06Next up, Pete with his highlights of what to see
0:18:06 > 0:18:08in this month's night sky.
0:18:09 > 0:18:12But first, here are his tips for capturing
0:18:12 > 0:18:16the full magnificence of one of the largest objects on view.
0:18:16 > 0:18:19As we enter the autumn, the nights are getting longer and longer
0:18:19 > 0:18:23and that means it's a perfect time to start doing some stargazing.
0:18:23 > 0:18:25One of the best objects to look for at this time of year
0:18:25 > 0:18:27is the Andromeda Galaxy.
0:18:28 > 0:18:31Like our own galaxy, Andromeda is a spiral.
0:18:33 > 0:18:35It's two and a half million light years away,
0:18:35 > 0:18:37making it one of the furthest objects
0:18:37 > 0:18:40it's possible to view with the naked eye.
0:18:41 > 0:18:43Now, with a reasonably dark, moonless sky,
0:18:43 > 0:18:46it should look like a faint, elongated smudge,
0:18:46 > 0:18:48but when you look at Andromeda,
0:18:48 > 0:18:50you may not be seeing the entire galaxy.
0:18:52 > 0:18:54The central core stands out much more clearly
0:18:54 > 0:18:58than the rest of the galaxy and is what many people see.
0:19:00 > 0:19:04But some of the best views of Andromeda come from photographing it,
0:19:04 > 0:19:07and depending on how you do it, its appearance can change dramatically.
0:19:10 > 0:19:13You can see this for yourself by taking a series of pictures
0:19:13 > 0:19:16and varying the exposures between each.
0:19:16 > 0:19:19I'll start with a relativity short exposure length
0:19:19 > 0:19:21of about 30 seconds or so.
0:19:25 > 0:19:30What you see here is very similar to what you'd see with the naked eye.
0:19:30 > 0:19:33That's just picked out the core of the galaxy there.
0:19:35 > 0:19:40As we increase the exposure time, more details start to come out.
0:19:40 > 0:19:44Past 60 seconds, the galaxy starts to take on a sharp edge,
0:19:44 > 0:19:47which is the result of a dust lane blocking starlight.
0:19:49 > 0:19:50As we up the exposure,
0:19:50 > 0:19:54the Andromeda Galaxy gets bigger and bigger.
0:19:56 > 0:19:59Now, in my earlier 30-second-exposure shot,
0:19:59 > 0:20:02all I picked out, really, was the core of the galaxy.
0:20:02 > 0:20:04Now, in this longer exposure,
0:20:04 > 0:20:07I can actually see the beautiful spiral arms either side
0:20:07 > 0:20:10of the core quite clearly, there.
0:20:10 > 0:20:15However you view it, Andromeda is a magnificent sight,
0:20:15 > 0:20:17and if you do capture its true size,
0:20:17 > 0:20:20it appears six times the width of a full moon.
0:20:22 > 0:20:27The Andromeda Galaxy is really easy to find in the night sky.
0:20:27 > 0:20:31Here's my guide to finding it and other highlights this month.
0:20:32 > 0:20:35A quick way to locate the Andromeda Galaxy,
0:20:35 > 0:20:37which is in the constellation of the same name,
0:20:37 > 0:20:41is to first identify the W-shaped pattern of Cassiopeia.
0:20:43 > 0:20:46The right half of the W is like an arrow,
0:20:46 > 0:20:50pointing down towards the star Mirach in the constellation of Andromeda.
0:20:52 > 0:20:57Look up slightly from Mirach to locate the fainter Mu Andromedae,
0:20:57 > 0:20:59and a little further up still
0:20:59 > 0:21:03to find the even fainter star Nu Andromedae.
0:21:04 > 0:21:08The Andromeda Galaxy sits slightly above and slightly right of Nu.
0:21:10 > 0:21:13Also this month, just before sunrise on the 20th,
0:21:13 > 0:21:16you'll be greeted by the magnificent sight of Jupiter
0:21:16 > 0:21:20next to a thin, waning crescent moon in the eastern part of the sky.
0:21:24 > 0:21:26Finally, on the 28th,
0:21:26 > 0:21:29look low down in the southwest about an hour after sunset
0:21:29 > 0:21:31to see planet Mars
0:21:31 > 0:21:34close to the similar-brightness star Antares in Scorpius.
0:21:36 > 0:21:39The name Antares literally means "the rival of Mars"
0:21:39 > 0:21:43because it's supposed to look just like the red planet.
0:21:43 > 0:21:46Now's your chance to check whether it really deserves that title.
0:21:50 > 0:21:52Now back to the hunt for ET.
0:21:53 > 0:21:56So, we've talked about what life is and where it can exist,
0:21:56 > 0:22:00but what are the odds of us actually finding life out in the cosmos?
0:22:00 > 0:22:0353 years ago, astrobiologist Frank Drake
0:22:03 > 0:22:05penned his famous equation
0:22:05 > 0:22:08which aimed at answering precisely this question,
0:22:08 > 0:22:11but we know much more about the universe now than we did then,
0:22:11 > 0:22:14and Maggie has been catching up with astrobioligist
0:22:14 > 0:22:17and alien hunter Duncan Forgan to find out how far we've got.
0:22:20 > 0:22:23The Drake equation is made up of a series of conditions
0:22:23 > 0:22:27that need to be met for us to communicate with alien life.
0:22:27 > 0:22:30Each letter represents one of these factors,
0:22:30 > 0:22:33such as how many stars have planets orbiting them?
0:22:33 > 0:22:35Or how many of these planets support life?
0:22:35 > 0:22:37Duncan is going to help me
0:22:37 > 0:22:39fill in these figures based on the latest research.
0:22:40 > 0:22:43When we start populating this, how does that work?
0:22:43 > 0:22:45Well, it gets a bit tricky to populate.
0:22:45 > 0:22:47When we start on the left-hand side,
0:22:47 > 0:22:50we're actually in the bits that we know quite well,
0:22:50 > 0:22:53and as we go across the terms, we get closer to the edge
0:22:53 > 0:22:56of our current understanding, and then we go past it into the unknown.
0:22:56 > 0:22:58OK, let's start at the beginning. Start with R.
0:22:58 > 0:23:01The rate of star formation in our galaxy.
0:23:01 > 0:23:03So the rate of star formation in our galaxy,
0:23:03 > 0:23:04the number we expect to see per year
0:23:04 > 0:23:06is somewhere between five and seven.
0:23:06 > 0:23:08So, why don't we start with just five? Five per year.
0:23:08 > 0:23:12- That's a nice, round number. - And conservative.- Conservative.
0:23:12 > 0:23:14So, fg - the number of stars that have a planet.
0:23:14 > 0:23:17That number has changed a lot, obviously, because we now
0:23:17 > 0:23:20know a lot about exoplanets that we didn't know 20 years ago.
0:23:20 > 0:23:24We think now that this particular f term is, in fact, one.
0:23:24 > 0:23:27So we're not assuming that all stars in the galaxy have planets,
0:23:27 > 0:23:30but many stars have multiple planets, so that keeps that at one.
0:23:30 > 0:23:33- Yes.- And that recent finding is from what we're doing with
0:23:33 > 0:23:34the exoplanets at the moment.
0:23:34 > 0:23:37Yes. This is cutting edge research right here.
0:23:37 > 0:23:39The next two terms relate to the number of those planets
0:23:39 > 0:23:43that can support life, that are habitable.
0:23:43 > 0:23:44So we're moving on to fp.
0:23:44 > 0:23:47fp is where it starts to get a bit trickier for us
0:23:47 > 0:23:50because now we have to start thinking about
0:23:50 > 0:23:52- what the word habitable means...- Oh.
0:23:52 > 0:23:56We don't have a good, strict definition of what life is, so that
0:23:56 > 0:23:59actually hampers our ability to then say, "What does life like?"
0:23:59 > 0:24:04- Yeah.- So if you want to put the frontier of science at this point,
0:24:04 > 0:24:07then it kind of exists here in this line.
0:24:07 > 0:24:11So we're now at this point where we've pushed our knowledge
0:24:11 > 0:24:13of the terms in Drake's equation all the way to here.
0:24:13 > 0:24:16I suppose, when Drake started, we were back here.
0:24:16 > 0:24:18Yeah, so Drake wrote this equation in 1961
0:24:18 > 0:24:21and he only had one term, but we've managed to push these things
0:24:21 > 0:24:24and, really, just in the last couple of years.
0:24:24 > 0:24:27In the last decade, we've really gone from...
0:24:27 > 0:24:29We were kind of here with the first detection of exoplanets
0:24:29 > 0:24:32about 20 years ago, and with the Kepler space telescope
0:24:32 > 0:24:35and other missions like it, we're really pushing
0:24:35 > 0:24:38in this direction now and we're picking up a bit of speed.
0:24:38 > 0:24:42But from here on in, it really does become guesswork.
0:24:42 > 0:24:45There's how frequently does life form?
0:24:46 > 0:24:49And the likelihood of that life being intelligent?
0:24:49 > 0:24:51But what do we mean by intelligence?
0:24:51 > 0:24:54There are many definitions of intelligence,
0:24:54 > 0:24:56and in this very strict definition of the sense,
0:24:56 > 0:24:58really, we became intelligent
0:24:58 > 0:25:01when we started sending strong radio signals out into space.
0:25:01 > 0:25:03And that was really only about 100 years ago.
0:25:03 > 0:25:07So we've not been "intelligent", quote, unquote, for very long.
0:25:07 > 0:25:08And the last term, L.
0:25:08 > 0:25:11The last term, L, is how long do we expect to see that signal?
0:25:11 > 0:25:13And what that really means is
0:25:13 > 0:25:15how long do we expect the civilisation to last?
0:25:15 > 0:25:17So you need to get that overlap of intelligence
0:25:17 > 0:25:19to actually make that communication.
0:25:19 > 0:25:21That's a very good point, and it kind of demonstrates
0:25:21 > 0:25:24that the galaxy is big in space, but it's also big in time.
0:25:24 > 0:25:28There's lots of time in the galaxy, so you've got to make sure that,
0:25:28 > 0:25:30if you want two civilisations to have a conversation,
0:25:30 > 0:25:33they have to be close in space and close in time at the same time.
0:25:33 > 0:25:36Duncan's speculates that the average civilisation
0:25:36 > 0:25:39will be able to communicate for 1,000 years.
0:25:39 > 0:25:42So what's the answer to the equation?
0:25:42 > 0:25:44It's about five.
0:25:44 > 0:25:47Five? But that's in the whole of the galaxy?
0:25:47 > 0:25:50No, that's at any one instant, if we looked up into the night sky,
0:25:50 > 0:25:53we'd expect to see five, and that includes us as well,
0:25:53 > 0:25:56- so we'd actually expect to see four. - THEY LAUGH
0:25:56 > 0:25:58I think that, fundamentally, it's a question we really want
0:25:58 > 0:26:02to answer and it's something that people have always wanted to answer.
0:26:02 > 0:26:04I think, for me, that's the beauty of this equation.
0:26:04 > 0:26:06In some way, it kind of encapsulates
0:26:06 > 0:26:09all of mankind's search to understand itself
0:26:09 > 0:26:12as well as understanding its place in the universe.
0:26:12 > 0:26:15So, you start with the terms that are to do with astronomy,
0:26:15 > 0:26:17physics, chemistry,
0:26:17 > 0:26:19and then you get onto the planetary sciences and the geology,
0:26:19 > 0:26:21and then you have the biology,
0:26:21 > 0:26:24and then as you get to the very end, you have to start thinking
0:26:24 > 0:26:26about the things that aren't the "hard" sciences,
0:26:26 > 0:26:28- but the social sciences.- Yes.
0:26:28 > 0:26:30You have to think about the psychology of life,
0:26:30 > 0:26:32you have to think about anthropology.
0:26:32 > 0:26:34The whole academic discipline of mankind is somehow
0:26:34 > 0:26:36encapsulated in these eight letters.
0:26:36 > 0:26:39- But I've never seen it in that way, so thank you very much.- Thank you.
0:26:39 > 0:26:42- A new perspective on the Drake equation.- Thank you.
0:26:46 > 0:26:47That's about it for this month,
0:26:47 > 0:26:50but we wanted to let you know about a fabulous competition
0:26:50 > 0:26:54being run by Blue Peter to design the official mission patch for our
0:26:54 > 0:26:58British astronaut Tim Peake's visit to the International Space Station.
0:26:58 > 0:27:01You need to be between the ages of six to 15 to enter.
0:27:01 > 0:27:03If you want more details of the competition,
0:27:03 > 0:27:06and the terms and conditions, please go to our website.
0:27:06 > 0:27:08The competition closes midday on 26th September,
0:27:08 > 0:27:11so do get your designs in.
0:27:11 > 0:27:13We can't leave you without mentioning Rosetta,
0:27:13 > 0:27:14ESA's comet chasing probe,
0:27:14 > 0:27:18now just 50km from Churyumov-Gerasimenko
0:27:18 > 0:27:21and getting ready for the touchdown of the Philae lander
0:27:21 > 0:27:23in just a few months' time.
0:27:23 > 0:27:26ESA have already identified five potential landing sites,
0:27:26 > 0:27:28which you can see up here,
0:27:28 > 0:27:30and they'll narrow that down to two in the next few weeks,
0:27:30 > 0:27:33but my favourite landing site is definitely J,
0:27:33 > 0:27:36because it's accessible. And they've just been travelling for so long.
0:27:36 > 0:27:40- I just want it to all go right, so go for the easy picking. - I think that's an engineer's view.
0:27:40 > 0:27:42As a scientist, I'm a big fan of what they're calling site A,
0:27:42 > 0:27:44which is on the larger lobe of the comet,
0:27:44 > 0:27:47the body of the rubber duck, if you think of the thing as a rubber duck.
0:27:47 > 0:27:50Land there and you get a view of both parts of the comet,
0:27:50 > 0:27:52and I think that would be really exciting.
0:27:52 > 0:27:54Good, but go for the easy pickings.
0:27:54 > 0:27:57But we'll be finding out exactly what they choose in the next few weeks.
0:27:57 > 0:27:59When we come back next month, we'll be talking about
0:27:59 > 0:28:03the outer edges of the solar system, its ice giants, Uranus and Neptune.
0:28:03 > 0:28:07- In the meantime, get outside and get looking up.- Good night.