0:00:33 > 0:00:37- BOTH: Hello.- Welcome to Herstmonceux Observatory in East Sussex,
0:00:37 > 0:00:39with its collection of impressive
0:00:39 > 0:00:42and elegant domes. They still have working telescopes here
0:00:42 > 0:00:46and enjoy wonderful dark skies, so I'm told, when it's clear.
0:00:46 > 0:00:50Well, we hope to enjoy those dark skies a little later with
0:00:50 > 0:00:52the Wealden Astronomical Society, but until then,
0:00:52 > 0:00:55we're going to talk about the lives and dramatic deaths of stars.
0:00:55 > 0:00:58And the team are here too, having a tug-of-war.
0:00:58 > 0:01:00We'll find out why later.
0:01:02 > 0:01:06Herstmonceux was built after the Second World War
0:01:06 > 0:01:10and became a Royal Observatory in 1958.
0:01:11 > 0:01:13Many of the telescopes came from Greenwich,
0:01:13 > 0:01:18where the London light pollution had become too much.
0:01:18 > 0:01:21Sir Patrick Moore was a regular visitor
0:01:21 > 0:01:24and supporter of the observatory, using the telescopes
0:01:24 > 0:01:29to look at the moon. Here he is in 1984.
0:01:29 > 0:01:32Of course, there are some features of the observatory
0:01:32 > 0:01:33which everybody knows.
0:01:33 > 0:01:36There is, for example, the time department.
0:01:36 > 0:01:38And here, the atomic clocks
0:01:38 > 0:01:40are now better timekeepers than the Earth itself.
0:01:40 > 0:01:43And it's also from here that the six pips come out.
0:01:43 > 0:01:46LOUD PIP
0:01:46 > 0:01:48Then there are the telescopes of Herstmonceux,
0:01:48 > 0:01:50which is another reason for our being here.
0:01:50 > 0:01:54In its heyday, 200 astronomers worked here
0:01:54 > 0:01:59and they looked at galaxies, nebula and even comets,
0:01:59 > 0:02:02but the majority of their work was with the stars.
0:02:02 > 0:02:06They mapped the stars in the sky, measured their distances, brightness
0:02:06 > 0:02:10and studied the light to see what the stars are made of.
0:02:12 > 0:02:16Stars make up a family and, like any family,
0:02:16 > 0:02:17the members are different.
0:02:17 > 0:02:21- Some stars are big.- Some small. - Some bright.- And some dim.
0:02:21 > 0:02:23But they're all essentially the same.
0:02:23 > 0:02:26They're vast balls of gas, mostly hydrogen.
0:02:26 > 0:02:29But the best star to look at is our own - the sun.
0:02:29 > 0:02:32And that's because, at the core of the sun, we know that
0:02:32 > 0:02:35the temperatures and the pressures are almost unimaginably vast.
0:02:35 > 0:02:39That means the atoms there are moving incredibly quickly.
0:02:39 > 0:02:42And when they collide, they can fuse together and as a consequence
0:02:42 > 0:02:48of the most famous equation - e=mc2 - matter is turned into light.
0:02:48 > 0:02:52And that happens at a furious rate. In fact, the sun is losing
0:02:52 > 0:02:56nearly 4 million tonnes of matter each and every second.
0:02:56 > 0:02:58So that's 4 million tonnes gone.
0:02:58 > 0:03:00And another 4 million tonnes gone.
0:03:00 > 0:03:03And that's happening all the time, in every one
0:03:03 > 0:03:06of the hundreds of billions of stars in our own galaxy.
0:03:06 > 0:03:09In fact, as stars go, the sun's not much to write home about.
0:03:09 > 0:03:14It's rather Mr Average. And so, it's time we met the rest of the family.
0:03:16 > 0:03:20There are hundreds of billions of stars in our own galaxy,
0:03:20 > 0:03:22but even from a good, dark spot,
0:03:22 > 0:03:26you'll have to content yourself with seeing just a few thousand of them.
0:03:26 > 0:03:29Even the largest telescopes won't show a star
0:03:29 > 0:03:33as anything other than a point of light, but we do see colour.
0:03:33 > 0:03:35Some stars are yellow, like our own sun,
0:03:35 > 0:03:38some red, and some blue.
0:03:38 > 0:03:41And it turns out that colour's important,
0:03:41 > 0:03:43because it tells us how hot the stars are.
0:03:45 > 0:03:47Lucie and I have come to a telescope
0:03:47 > 0:03:50that's spent many a night staring at the stars.
0:03:52 > 0:03:57Fantastic. So here we have the 1896 26-inch Thomson Refractor.
0:03:57 > 0:03:59- It's beautiful, isn't it?- Fantastic.
0:03:59 > 0:04:02Always good to see a proper refractor in a giant dome.
0:04:02 > 0:04:04This is what observatories are supposed to look like.
0:04:04 > 0:04:07And they used to do measurements of star positions from here.
0:04:07 > 0:04:09And not just positions.
0:04:09 > 0:04:12This telescope was used to measure the distances to the stars.
0:04:12 > 0:04:15But that's not the most interesting thing about this telescope.
0:04:15 > 0:04:20It does something really special. Let me show you. Come round here.
0:04:20 > 0:04:22- OK, I'm slightly nervous. - SHE LAUGHS
0:04:22 > 0:04:25When you start running for...for switches.
0:04:25 > 0:04:28- Hold onto your hats. - OK.- Here we go.
0:04:28 > 0:04:31LOUD THUD, CHRIS LAUGHS
0:04:31 > 0:04:34So we do not have to move the telescope. We go to the telescope.
0:04:34 > 0:04:38This is the civilised way to get to your observing position.
0:04:38 > 0:04:39Move the entire floor.
0:04:39 > 0:04:41- This is fabulous! - LUCIE LAUGHS
0:04:41 > 0:04:44- But you need to watch out for your head, Chris.- Right, thank you.
0:04:44 > 0:04:46I've been told it stops automatically. I'm just going
0:04:46 > 0:04:49- to keep pressing until it does. - Are you sure this stops?
0:04:49 > 0:04:51I'm willing... Yes!
0:04:51 > 0:04:53- There we go.- There we go.- Perfect.
0:04:53 > 0:04:56- So what a civilised way to get up to do the observing.- It's great.
0:04:56 > 0:04:59- And now, here we are and we can go look at the sky.- Yeah, fantastic!
0:05:02 > 0:05:05Over 100 years ago, astronomers were trying to make sense
0:05:05 > 0:05:09of the assortment of stars in the night sky.
0:05:09 > 0:05:13Two men - American Henry Russell and Dane Ejnar Hertzsprung -
0:05:13 > 0:05:15realised that the key was showing
0:05:15 > 0:05:19how the brightness of a star is related to its colour.
0:05:21 > 0:05:24So what we've got here are the two things we know about stars.
0:05:24 > 0:05:26We've got their colour, but colour means temperature,
0:05:26 > 0:05:28so the red stars are the coolest
0:05:28 > 0:05:30and the blue, white ones are the hottest.
0:05:30 > 0:05:32It's the opposite way round from bathroom taps.
0:05:32 > 0:05:34Red is cool, blue is hot.
0:05:34 > 0:05:38And the other piece of information is how bright the star is.
0:05:38 > 0:05:40So faint ones go down here
0:05:40 > 0:05:42and bright ones go up here.
0:05:42 > 0:05:45So now all we need is to put some stars on our board
0:05:45 > 0:05:48and, in fact, we've got some in our pocket.
0:05:48 > 0:05:51And the first one that we can put on is the most familiar star - the sun.
0:05:51 > 0:05:55And it turns out the sun goes bang in the middle of our diagram here.
0:05:55 > 0:05:57Surface temperature of about 6,000 Kelvin,
0:05:57 > 0:06:02so halfway along here and then, medium brightness as well.
0:06:02 > 0:06:06We can also do the brightest star in the sky and that's Sirius.
0:06:06 > 0:06:08And Sirius is a bit hotter and a bit brighter than our sun,
0:06:08 > 0:06:10so that goes up here.
0:06:10 > 0:06:13The nearest star system to our own is made up of Alpha Centauri.
0:06:13 > 0:06:16A bit hotter, a bit brighter than the sun. That has a companion,
0:06:16 > 0:06:18Alpha Centauri B, which is a bit fainter.
0:06:18 > 0:06:22Put it down there. And then, the nearest star to the sun, Proxima,
0:06:22 > 0:06:25red, much smaller, much fainter, so that goes down there.
0:06:25 > 0:06:27Now, I want to extend it up here a little bit,
0:06:27 > 0:06:31so I'm going to put on Spica, which is a staggering 12,000 times
0:06:31 > 0:06:35as bright as our sun, but because it's over 200 light-years away,
0:06:35 > 0:06:37it's a little bit fainter, how we see it,
0:06:37 > 0:06:40but it is bright in reality and it goes up here.
0:06:40 > 0:06:43And lots of our familiar bright stars in the night sky go here,
0:06:43 > 0:06:45so Vega sits about there as well.
0:06:45 > 0:06:47And then, if we add a few more stars,
0:06:47 > 0:06:49we begin to see that they fill in the gaps.
0:06:49 > 0:06:54And actually, what's really clear is that all the stars lie along
0:06:54 > 0:06:57one line in our diagram and that tells us something really important.
0:06:57 > 0:07:01They're all fusing hydrogen to helium in their cores.
0:07:01 > 0:07:02That's what's powering them.
0:07:05 > 0:07:09It's what we astronomers call the main sequence.
0:07:09 > 0:07:12But not all stars sit here.
0:07:12 > 0:07:16There are hot bright stars called blue giants, like Deneb,
0:07:16 > 0:07:19and then there are the red giants, like Arcturus,
0:07:19 > 0:07:21which our sun will become in its old age.
0:07:23 > 0:07:25These fuse helium at their core
0:07:25 > 0:07:28causing them to swell to enormous proportions.
0:07:30 > 0:07:33It's hard to get your head round the sizes of the stars,
0:07:33 > 0:07:36but luckily, I've got an onion and I want you to imagine
0:07:36 > 0:07:39that this onion is the size of the sun as it is today.
0:07:39 > 0:07:41But the sun won't stay that size forever.
0:07:41 > 0:07:45When it turns into a red giant 4,500 million years from now,
0:07:45 > 0:07:48it will swell up from the size of the onion
0:07:48 > 0:07:52to be the size of the dome and that will encompass the Earth's orbit.
0:07:52 > 0:07:54And if that's not impressive enough, Betelgeuse,
0:07:54 > 0:07:56one of the biggest of the stars,
0:07:56 > 0:08:00so large - ten times larger in fact than Jupiter's orbit -
0:08:00 > 0:08:01would fit inside it.
0:08:03 > 0:08:06Stars don't collapse because of pressure from the core,
0:08:06 > 0:08:08pushing up against gravity.
0:08:09 > 0:08:13As the star grows old, these two forces strain against each other,
0:08:13 > 0:08:15rather like a tug-of-war.
0:08:15 > 0:08:18JON CULSHAW, LIKE A BBC SPORTS COMMENTATOR: 'And you join us here
0:08:18 > 0:08:21'for our stellar tug-of-war! We have two teams, Team Gravity,
0:08:21 > 0:08:25'an ever present force, trying to pull everything inwards!
0:08:25 > 0:08:30'And then, there is Team Star, which has energy and pressure on its side,
0:08:30 > 0:08:33'resisting the pull of gravity. Team Star is nuclear!
0:08:33 > 0:08:37'They are burning hydrogen and you can feel the heat!
0:08:38 > 0:08:40'Team Gravity, though, they never give up.
0:08:40 > 0:08:43'They are a force to be reckoned with!'
0:08:44 > 0:08:48We stand a better chance of survival if we work together.
0:08:53 > 0:08:58'Team Star, quite magnificent, producing just enough heat and light
0:08:58 > 0:09:00'to balance gravity! Absolute stalemate here!
0:09:00 > 0:09:03TEAMS GRUNT
0:09:03 > 0:09:07'But Team Star running out of steam! The hydrogen has all but gone here!
0:09:07 > 0:09:10'They are beginning to collapse!
0:09:10 > 0:09:13'Team Gravity sensing success here, surely!'
0:09:14 > 0:09:16LOUD GRUNTING
0:09:16 > 0:09:20'But, but, hang on a minute, deep in the core, things are heating up here!
0:09:20 > 0:09:23'Team Star are fighting right back. Suddenly, they're right back in it,
0:09:23 > 0:09:28'burning helium, a surge in the energy! Team Star is now a red giant
0:09:28 > 0:09:30'and the crowd love it!' CHEERING
0:09:30 > 0:09:33'Gravity on the run here, you would have to say, Derek!
0:09:33 > 0:09:36'But hold on a minute! Team Star has spent their fuel.
0:09:36 > 0:09:40'They have burned up. They're all gone. Nothing left.
0:09:40 > 0:09:44'And Gravity continues pulling in and the star collapses.
0:09:44 > 0:09:48'It becomes a quite spectacular nebula
0:09:48 > 0:09:50'with a tiny white dwarf at its heart.
0:09:50 > 0:09:53'Gravity wins the day! Remarkable.'
0:09:56 > 0:10:01Eventually, the outer layers of the sun will be expelled into space,
0:10:01 > 0:10:03becoming a planetary nebula.
0:10:03 > 0:10:05The core, called a white dwarf,
0:10:05 > 0:10:09will be all that remains of our once mighty star.
0:10:09 > 0:10:13We see lots of planetary nebulae in our night sky.
0:10:13 > 0:10:19They are beautiful and ephemeral. The death of a star caught in time.
0:10:19 > 0:10:21The most massive stars,
0:10:21 > 0:10:24like hot blue Deneb, don't die quietly.
0:10:24 > 0:10:26Once their fuel is consumed,
0:10:26 > 0:10:28the star collapses
0:10:28 > 0:10:32and the result is one of the most violent explosions in the universe.
0:10:32 > 0:10:35We call it a supernova.
0:10:40 > 0:10:45These cataclysmic stellar deaths can outshine an entire galaxy,
0:10:45 > 0:10:50and, in 1987, we were treated to one in a galaxy on our cosmic doorstep
0:10:50 > 0:10:52in the nearby Large Magellanic Cloud.
0:10:54 > 0:10:57The object, called Supernova 1987A,
0:10:57 > 0:10:59has been studied in great detail ever since,
0:10:59 > 0:11:03and astronomers have watched the glowing rings of material
0:11:03 > 0:11:05spreading out into the cosmos.
0:11:09 > 0:11:12You can see the remnants of supernovae in the night sky
0:11:12 > 0:11:15with even a moderately-sized telescope.
0:11:17 > 0:11:19Nearly 1,000 years ago,
0:11:19 > 0:11:23a blue giant star exploded in the constellation of Taurus.
0:11:23 > 0:11:26And we see it today as the Crab Nebula.
0:11:29 > 0:11:34The astronomers at Herstmonceux studied these objects and many more.
0:11:34 > 0:11:37And Jon's been finding out what it was like to work here.
0:11:40 > 0:11:43Life for an astronomer at Herstmonceux was busy,
0:11:43 > 0:11:46observing by night and day.
0:11:46 > 0:11:50With all the telescopes working at night-time in the Sussex countryside,
0:11:50 > 0:11:52it must have been an active and exciting place to be.
0:11:54 > 0:11:55But there was time for some R and R,
0:11:55 > 0:11:58with some interesting accommodation next door.
0:11:58 > 0:12:03Not every astronomer gets the chance to sleep in a 15th-century castle.
0:12:03 > 0:12:08The observatories were purpose built to fit in with the castle setting.
0:12:08 > 0:12:12A flint knapper was brought out of retirement to finish the outsides
0:12:12 > 0:12:15and the copper domes finished in verdigris.
0:12:15 > 0:12:19But unfortunately, all the effort building this magnificent facility
0:12:19 > 0:12:23couldn't improve the British weather. Almost as soon as it was finished,
0:12:23 > 0:12:25plans were afoot to move to the Canary Islands,
0:12:25 > 0:12:30where the seeing was better and, by 1990, the observatory closed.
0:12:31 > 0:12:35Dr Graham Appleby was a solar observer here.
0:12:37 > 0:12:41So, Graham, you worked here from 1970 to 1990.
0:12:41 > 0:12:45Really the heyday of Herstmonceux as a Royal Observatory.
0:12:45 > 0:12:48What are some of your most memorable observations
0:12:48 > 0:12:51and studies that would have happened during that time?
0:12:51 > 0:12:53I began observing the sun.
0:12:53 > 0:12:55My first job was looking
0:12:55 > 0:12:57at the sunspots through hydrogen-alpha filters
0:12:57 > 0:13:00and flares. It was a very active time in the sun,
0:13:00 > 0:13:05so it was amazing to see, from the ground, these sunspots erupting.
0:13:05 > 0:13:07Then I got involved in observing the moon,
0:13:07 > 0:13:09the passage of the moon across in front of stars,
0:13:09 > 0:13:11so looking at that was very exciting as well.
0:13:11 > 0:13:14And as observatories go, it's a very beautiful place.
0:13:14 > 0:13:16- Yes.- Wonderfully landscaped and so on.
0:13:16 > 0:13:19But some of the astronomers, in the early days that this was crafted,
0:13:19 > 0:13:21were a little sceptical about that.
0:13:21 > 0:13:24- You don't need a pond when you're studying the stars at night.- Exactly.
0:13:24 > 0:13:26Imagine this completely dark, some little lights may be glowing,
0:13:26 > 0:13:28but you come out of this dome up here,
0:13:28 > 0:13:33which I worked in quite a lot, Dome D, it has a 10 centimetre refractor.
0:13:33 > 0:13:36We used to use it to observe minor planets.
0:13:36 > 0:13:38And you can imagine coming out of the steps there and,
0:13:38 > 0:13:41if you make a wrong turn, you're in the pond.
0:13:41 > 0:13:43So it's not the best design.
0:13:43 > 0:13:47It looks great, but it's not the best design for a dark observatory.
0:13:48 > 0:13:52But now, Herstmonceux is this wonderful visitor centre
0:13:52 > 0:13:55and scientific centre and a great place for astronomy outreach.
0:13:55 > 0:13:58Lots of people being inspired as they visit here,
0:13:58 > 0:14:01so sort of a new kind of heyday, isn't it now?
0:14:01 > 0:14:04Yes, to see these older telescopes now being used for education
0:14:04 > 0:14:07is a perfect link, actually, is a perfect result.
0:14:07 > 0:14:10Patrick himself was a great, great fan of this place.
0:14:10 > 0:14:12So I'm sure he'd be delighted to see it
0:14:12 > 0:14:14as this great centre of outreach for astronomy,
0:14:14 > 0:14:18sparking new interests in astronomy all the time as people visit.
0:14:21 > 0:14:25The observatory here shone brightly, but all too briefly.
0:14:29 > 0:14:31'Chris North and I are going to see
0:14:31 > 0:14:35'how they used to study the light from stars.'
0:14:35 > 0:14:38Here, we've got the largest telescope on the site -
0:14:38 > 0:14:41the 36 inch yapp reflector.
0:14:41 > 0:14:43It's built in the 1930s, moved here in the '50s,
0:14:43 > 0:14:46and it's quite a remarkable feat of engineering, isn't it?
0:14:46 > 0:14:50It is wonderfully imposing to see it, really arresting as you walk in.
0:14:50 > 0:14:52This, of course, adapted for spectroscopy,
0:14:52 > 0:14:57so it can decode and specifically study starlight and really tell us
0:14:57 > 0:15:00about the signature of stars and show us their uniqueness.
0:15:00 > 0:15:04So you can do this with a prism, split the sun's light, or you can
0:15:04 > 0:15:07- even create the same effect using the back of a CD.- Exactly.
0:15:07 > 0:15:10But to see the light from other stars that are fainter than the sun,
0:15:10 > 0:15:12you've actually got to use a telescope like this to
0:15:12 > 0:15:15collect enough light, because they are so much fainter than the sun.
0:15:15 > 0:15:18When we do that, we see something quite remarkable in the spectrum.
0:15:18 > 0:15:20- I imagine this would collect rather a lot of light.- Yes.
0:15:20 > 0:15:23- And give us the chance that we could study it over here.- Indeed.
0:15:24 > 0:15:28Ah! There was one of these on Mr Dwyer's laboratory wall at school.
0:15:28 > 0:15:31They're very decorative, but what do they tell us?
0:15:31 > 0:15:32This is the sun, right?
0:15:32 > 0:15:36So this is a representation of the light from the sun,
0:15:36 > 0:15:39split out into its rainbow, its spectrum of colours.
0:15:39 > 0:15:42And it goes from red through purple, as you might expect,
0:15:42 > 0:15:45but there are specific colours that appear much darker
0:15:45 > 0:15:49and that's because those very specific colours, like this one,
0:15:49 > 0:15:52absorbed by specific types of elements in the sun's atmosphere,
0:15:52 > 0:15:55so this one, in the red end of the spectrum,
0:15:55 > 0:15:58is absorbed by hydrogen in the sun's atmosphere
0:15:58 > 0:16:00and there are other elements as well, so hydrogen absorbs
0:16:00 > 0:16:03at this wavelength and other wavelengths as well. But we can
0:16:03 > 0:16:07also see that there's small amounts of calcium in the sun's atmosphere
0:16:07 > 0:16:09and the small amounts of iron in the sun's atmosphere.
0:16:09 > 0:16:13We can start to get a spectral fingerprint
0:16:13 > 0:16:16- of what the sun is made of. - And the chart above.
0:16:16 > 0:16:18Now, this is from a blue giant star.
0:16:18 > 0:16:20Some of the lines are in a similar position,
0:16:20 > 0:16:22but there's a lot that's different about it.
0:16:22 > 0:16:24What differences are we seeing there?
0:16:24 > 0:16:27So the first thing about the blue giant star is that
0:16:27 > 0:16:30it's very bright in the blue, but it's very dim in the red
0:16:30 > 0:16:32and that's because the star is much hotter.
0:16:32 > 0:16:34The fact that the star's a lot hotter also means that
0:16:34 > 0:16:36some of those elements in the atmosphere
0:16:36 > 0:16:39are completely stripped of their electrons already.
0:16:39 > 0:16:41Now that means they can't absorb any light,
0:16:41 > 0:16:45so we don't see absorption lines, as these are called,
0:16:45 > 0:16:48from iron and from calcium and that kind of thing.
0:16:48 > 0:16:52We mainly just see hydrogen in the atmospheres of those stars.
0:16:52 > 0:16:55So we had the diagram - the HertzsprungRussell diagram
0:16:55 > 0:16:57that Chris and Lucie were showing us earlier -
0:16:57 > 0:17:00and we had the sun right in the middle,
0:17:00 > 0:17:02and the hot blue stars up on the top left,
0:17:02 > 0:17:05then, down the bottom right, we had the cold red stars.
0:17:05 > 0:17:08And this is one of those cooler red stars.
0:17:08 > 0:17:10We can see that it's very bright in the red
0:17:10 > 0:17:13and it's much fainter in the blue. That tells us it's much cooler.
0:17:13 > 0:17:16But also, the spectrum's a lot busier.
0:17:16 > 0:17:18There's an awful lot more lines in there.
0:17:18 > 0:17:21And whereas the atmospheres of these stars, these warmer stars,
0:17:21 > 0:17:24are dominated just by atoms in their atmospheres,
0:17:24 > 0:17:27in cooler stars, you can have molecules. You can have chemistry.
0:17:27 > 0:17:30This is atoms joined together. Molecules absorb light
0:17:30 > 0:17:34at many, many more colours than just the pure atoms do.
0:17:34 > 0:17:36And if you go to even colder temperatures too,
0:17:36 > 0:17:38things get even more complex,
0:17:38 > 0:17:41because not only do you get redder and redder
0:17:41 > 0:17:45until you're almost invisible to the light we see with our eyes,
0:17:45 > 0:17:48not only do you have molecules and chemistry in the atmosphere,
0:17:48 > 0:17:51you get something you really wouldn't expect. You get weather.
0:17:51 > 0:17:55And you certainly don't associate that taking place on a star
0:17:55 > 0:17:57and this takes us to that strange world of the brown dwarf.
0:17:57 > 0:18:02A very curious object, sort of like a duck-billed platypus, in a way.
0:18:02 > 0:18:04Hard to classify exactly what they are.
0:18:07 > 0:18:11- LUCIE:- Brown dwarves are a new addition to our star chart
0:18:11 > 0:18:15and are the coolest and dimmest of stars.
0:18:15 > 0:18:18Hertzsprung and Russell could only have dreamed
0:18:18 > 0:18:20of these strange beasts.
0:18:22 > 0:18:25Part of the difficulty has been seeing them,
0:18:25 > 0:18:29because they don't shine brightly like our star.
0:18:29 > 0:18:31To find them, we need infrared telescopes,
0:18:31 > 0:18:34which can pick out cool objects.
0:18:36 > 0:18:39'Ben Burningham from the University of Hertfordshire
0:18:39 > 0:18:41'is a brown dwarf hunter.
0:18:43 > 0:18:47'He uses space telescopes like Spitzer and WISE
0:18:47 > 0:18:51'to look for these elusive beasts of the star family,
0:18:51 > 0:18:54'which lurk in the cold dark parts of space.'
0:18:54 > 0:18:56They're very peculiar objects.
0:18:56 > 0:18:59I'm sort of struggling to conceptualise where they sit.
0:18:59 > 0:19:02They seem a bit like the missing link in between stars and planets somehow.
0:19:02 > 0:19:05They certainly are the missing link between stars and planets.
0:19:05 > 0:19:07The warmer ones look a lot like stars.
0:19:07 > 0:19:09They show a lot of the behaviour we see stars having,
0:19:09 > 0:19:12but then, the lowest mass ones look like planets.
0:19:12 > 0:19:15They have weather, for example. You see dust cloud weather and things
0:19:15 > 0:19:17at sort of about 1,000 degrees centigrade.
0:19:17 > 0:19:20So you go from studying the kind of plasma physics
0:19:20 > 0:19:23of charged particles in a stellar atmosphere
0:19:23 > 0:19:25with protons and electrons flying around
0:19:25 > 0:19:27to atmospheric chemistry, where you're using
0:19:27 > 0:19:31the language of planetary science rather than stellar physics.
0:19:31 > 0:19:33And what kind of temperatures are we talking about here?
0:19:33 > 0:19:36Well, they range from the temperatures of the coolest stars -
0:19:36 > 0:19:40at about 1,700 degrees centigrade - to much, much lower temperatures.
0:19:40 > 0:19:43In fact, a few years ago, I was very pleased when I pushed the record
0:19:43 > 0:19:46along with a team of astronomers at Hertfordshire to down
0:19:46 > 0:19:49to about 500 Kelvin, which we thought was about good for oven chips.
0:19:49 > 0:19:51Yeah, congratulations on that record.
0:19:51 > 0:19:54Well, yeah, it's been taken pretty comprehensively now.
0:19:54 > 0:19:56The WISE Mission, a satellite from NASA,
0:19:56 > 0:19:59has managed to push the temperature limit down to about 300 Kelvin,
0:19:59 > 0:20:01which is room temperature.
0:20:01 > 0:20:04- Hang on, room temperature? - Yeah.- Like this temperature?
0:20:04 > 0:20:06A bit warmer than this temperature. CHRIS LAUGHS
0:20:06 > 0:20:09But, um, but yeah, about 300 Kelvin, 20 degrees centigrade.
0:20:09 > 0:20:13So how do you say whether something is a star
0:20:13 > 0:20:16- or whether something is a planet? - Well, that's tricky.
0:20:16 > 0:20:18So people tend to take a kind of gut feeling approach.
0:20:18 > 0:20:21Does the thing taste like a planet, does it smell like a planet?
0:20:21 > 0:20:25The definition, officially, is when something is low enough mass
0:20:25 > 0:20:27that it doesn't burn something called deuterium in the core
0:20:27 > 0:20:30- when it's very young. - Like heavy hydrogen?- Yeah.
0:20:30 > 0:20:32Whether it burns that in the core when it's very young,
0:20:32 > 0:20:34then we call it a planet if it's orbiting a star.
0:20:34 > 0:20:37Um, they have, er, atmospheres that are predominantly
0:20:37 > 0:20:41composed of hydrogen, but the molecules we see in the atmosphere,
0:20:41 > 0:20:44so things like water, methane and, at the coldest temperatures, ammonia.
0:20:44 > 0:20:47And it's probable that, when we get to these temperatures,
0:20:47 > 0:20:50we'll start to see water clouds in their atmospheres.
0:20:50 > 0:20:53Where are the nearest brown dwarfs? How close are they to us?
0:20:53 > 0:20:55Well, they're very close.
0:20:55 > 0:20:58In fact, just recently, an American astronomer, working on his own
0:20:58 > 0:21:00looking through the WISE dataset,
0:21:00 > 0:21:03found a brown dwarf within six light years of Earth,
0:21:03 > 0:21:06which makes it one of the closest object to the sun.
0:21:06 > 0:21:09- What, the third closest stellar system?- Yeah.- Something like that.
0:21:09 > 0:21:11- Yeah.- And we had no idea it was there?- No idea at all.
0:21:11 > 0:21:14It was hiding against the crowded background of the galactic plain.
0:21:14 > 0:21:17Lots of people have been looking, but it's a very hard job
0:21:17 > 0:21:20to find these things and a lot of people were kicking themselves.
0:21:20 > 0:21:24It seems slightly careless to have missed a starlike object that close.
0:21:24 > 0:21:26Careless is a strong word. LAUGHTER
0:21:26 > 0:21:28Sorry, I don't mean to be rude.
0:21:28 > 0:21:31- I guess it shows how little we know about the galaxy.- Very hard, yeah.
0:21:31 > 0:21:36- So is that the closest one?- That's very hard to say. Um, probably not.
0:21:36 > 0:21:39I would say, if we're still finding things at six light years,
0:21:39 > 0:21:42there may be things even closer. Um, it would be pretty ambitious
0:21:42 > 0:21:45to say that's definitely the closest one.
0:21:45 > 0:21:48'The other odd thing about these stars
0:21:48 > 0:21:50'is that they don't seem to die.'
0:21:50 > 0:21:53They just get colder and colder.
0:21:53 > 0:21:55They are immortal stars
0:21:55 > 0:21:59ending their lives in the lonely emptiness of space.
0:22:01 > 0:22:04We're hoping to see some brighter stars tonight.
0:22:04 > 0:22:07Wealden Astronomical Society is resident here
0:22:07 > 0:22:10and they've joined us to keep us company.
0:22:11 > 0:22:13Paul is talking to John Pilbeam
0:22:13 > 0:22:17about some objects we hope to see later.
0:22:17 > 0:22:19What sort of area
0:22:19 > 0:22:22of amateur astronomy is your particular thing? What grabs you?
0:22:22 > 0:22:25Star clusters, and double stars. I love double stars, yeah.
0:22:25 > 0:22:28I don't often hear people say that, actually.
0:22:28 > 0:22:31- Like the really geeky aspects... - I know.- ..of amateur astronomy.
0:22:31 > 0:22:33- What's your favourite double star? - Albireo.
0:22:33 > 0:22:36- I think we've got to say that. - I have to.- It's quite nice.
0:22:36 > 0:22:38Andromeda, I think, has a nice...
0:22:38 > 0:22:40is second one to that with the coloured stars,
0:22:40 > 0:22:43- but Albireo is the favourite. - The lovely orange and blue.
0:22:43 > 0:22:46- It really is. - It is the blue that catches you.
0:22:46 > 0:22:51Gary Palmer likes studying my favourite star - our sun.
0:22:51 > 0:22:55Pete's finding out why he enjoys solar observing so much.
0:22:55 > 0:22:57It's the perfect thing for the public,
0:22:57 > 0:23:01- cos it's during the day.- That's right, yeah. It's also nicer for me,
0:23:01 > 0:23:04- cos I keep warmer, so, um... - LAUGHTER
0:23:04 > 0:23:08- No, I've seen some of your pictures and they are spectacular.- Thank you.
0:23:08 > 0:23:10And you specialise particularly
0:23:10 > 0:23:13- in what's known as hydrogen alpha imaging...- Yeah.
0:23:13 > 0:23:15..which is taking pictures of the sun's chromosphere,
0:23:15 > 0:23:17the prominences and whatever going on.
0:23:17 > 0:23:20- You've been looking at the sun today, haven't you?- Yeah.
0:23:20 > 0:23:23It's been really interesting today. There's some nice detail on there.
0:23:23 > 0:23:25I have been fighting with the wind and clouds a little.
0:23:25 > 0:23:29- A bit windy, yeah.- Um, but did manage to get some nice images.
0:23:29 > 0:23:33- Right, anything particularly stand out?- Yeah, there was a nice flare
0:23:33 > 0:23:35that came off the edge of the sun earlier on,
0:23:35 > 0:23:38- and gradually developed into a nice loop prominence.- Oh, really?
0:23:38 > 0:23:41- They're fantastic!- It was really nice, yeah, lovely to watch.
0:23:41 > 0:23:45And there was a lovely large prominence coming off.
0:23:45 > 0:23:48That had some fantastic shapes in there.
0:23:48 > 0:23:50Um, and also, a lot of sunspots,
0:23:50 > 0:23:53so it seems like there's a lot of activity starting again.
0:23:53 > 0:23:56- Do you think the sun's starting to wake up a bit?- I think so.
0:23:56 > 0:23:59- About time. - Yeah, it's very, very late.
0:23:59 > 0:24:01It's a little bit like our summer this year.
0:24:07 > 0:24:12JON: So, Paul and Pete, what of the stars in the June sky at the moment?
0:24:12 > 0:24:14We're waiting for the clouds to co-operate. It looks like
0:24:14 > 0:24:17- more are blowing in.- It doesn't look promising.- Not at the moment,
0:24:17 > 0:24:21- but at least June is the time for the noctilucent clouds.- Ah, yes.
0:24:21 > 0:24:24- We like those.- We do. - Pete's obsessed with them.
0:24:24 > 0:24:27They're great, because the nights in June are really, really short,
0:24:27 > 0:24:30so these are things that are easy to see, if they're there.
0:24:30 > 0:24:33They glow with an electric blue light,
0:24:33 > 0:24:35like a network of clouds in the night sky.
0:24:35 > 0:24:38They're really high altitude clouds, they're picking up
0:24:38 > 0:24:41the light reflecting off them from the sun, which is below the horizon.
0:24:41 > 0:24:45- They're something which are unique to the summertime.- They do have that
0:24:45 > 0:24:48- wonderful ethereal glow to them. - They do and the interesting thing is
0:24:48 > 0:24:51how subtly they can change over the course of 10-15 minutes.
0:24:51 > 0:24:54They really are dynamic objects. Lovely things.
0:24:54 > 0:24:56And June also the time of the moon's perigee,
0:24:56 > 0:24:59- the super moon, as they call it. - That's right. This is one
0:24:59 > 0:25:03of those events that normally gets people very excited, doesn't it?
0:25:03 > 0:25:05The moon is going to be
0:25:05 > 0:25:07a tiny fraction of a bit larger in the sky.
0:25:07 > 0:25:10It's actually 23rd of June and it's because the moon
0:25:10 > 0:25:12- is at the closest point in its orbit.- Perigee.
0:25:12 > 0:25:15And that coincides with it being full moon this time.
0:25:15 > 0:25:18It has the name super moon. That's actually an astrological term.
0:25:18 > 0:25:21- We won't have such things here! - Astrologers brought it in.
0:25:21 > 0:25:23- Don't mention them again! - Let's say perigee moon.
0:25:23 > 0:25:25Well, spectacular as that moon will be,
0:25:25 > 0:25:27hopefully it won't wash the stars out too much.
0:25:27 > 0:25:30So which particular ones should we be looking out for in June?
0:25:30 > 0:25:34Well, the lives and deaths of stars, something we've looked at on the programme.
0:25:34 > 0:25:36We've got those in the summer night sky,
0:25:36 > 0:25:40so let's start with star clusters and the wild duck cluster,
0:25:40 > 0:25:42- M11, is a good one, isn't it? - Lovely, actually.
0:25:42 > 0:25:44That's at the bottom of Aquila the eagle.
0:25:44 > 0:25:46A little curve of stars points to it.
0:25:46 > 0:25:49When you look at it through a telescope...
0:25:49 > 0:25:52Even a small telescope will show a beautiful smattering of stars there.
0:25:52 > 0:25:54They're supposed to be arranged in a sort of V shape,
0:25:54 > 0:25:57which is supposed to look like a cluster of wild ducks
0:25:57 > 0:26:00- flying across the sky.- It does look a bit like what it's supposed to.
0:26:00 > 0:26:03- One of those rare objects... - You've got a good imagination,
0:26:03 > 0:26:04because I've never seen that.
0:26:04 > 0:26:07- LAUGHTER - So viewers' imagination!
0:26:07 > 0:26:09But we also have a nice globular cluster.
0:26:09 > 0:26:12It's low down in the constellation of Sagittarius.
0:26:12 > 0:26:14- This is in your teapot asterism, isn't it?- That's right.
0:26:14 > 0:26:16It's at the heart of Sagittarius,
0:26:16 > 0:26:20which sort of marks the region where the centre of the Milky Way is.
0:26:20 > 0:26:23- It looks exactly like a teapot. - Not exactly!- Oh, it does!
0:26:23 > 0:26:26It's exactly like a teapot. But if you imagine where steam would
0:26:26 > 0:26:29rise out of the spout of the teapot, loads of stuff around there.
0:26:29 > 0:26:32You've got the Lagoon Nebula, which is one of only two
0:26:32 > 0:26:36areas of nebulosity you can see with the naked eye in the night sky.
0:26:36 > 0:26:38You've got the Trifid Nebula, which is a beautiful thing
0:26:38 > 0:26:41to look at through a telescope. Three dark lanes cuts it into three.
0:26:41 > 0:26:45And then, you've also got M22, which is the brightest globular cluster
0:26:45 > 0:26:48which can be seen from the northern hemisphere,
0:26:48 > 0:26:51and you've got M25, which is another beautiful cluster.
0:26:51 > 0:26:54- A deep sky treasure trove. - It is, absolutely.
0:26:54 > 0:26:57It's a pity it's so low down, that's the only unfortunate thing about it.
0:26:57 > 0:27:00Well, at the other end of the spectrum, we have star death,
0:27:00 > 0:27:03and this is represented by a fine selection of planetary nebula.
0:27:03 > 0:27:06In particular, I think, the Ring Nebula in Lyra
0:27:06 > 0:27:07is a really fine example of this.
0:27:07 > 0:27:09I think you should try this in London, Jon.
0:27:09 > 0:27:11I think that telescope of yours would pick it up.
0:27:11 > 0:27:14And if you've got a large enough power, and conditions are good,
0:27:14 > 0:27:18you see a sort of ghostly smoke ring in the sky.
0:27:18 > 0:27:21Well, there's a fine thing to look out for. June full of promise.
0:27:21 > 0:27:24- And, hopefully, some clear skies.- Yes!
0:27:27 > 0:27:31Many fine objects to observe in June, so long as the weather co-operates
0:27:31 > 0:27:35and you can use Pete's sky charts to help locate them,
0:27:35 > 0:27:37including the teapot and its steam, if you like.
0:27:37 > 0:27:39Just go to our website...
0:27:46 > 0:27:51We have had no luck with the weather and it's even starting to rain.
0:27:51 > 0:27:54Wealden Astronomical Society are packing up.
0:27:54 > 0:28:00Let's hope, next time, we come and enjoy Herstmonceux's dark skies.
0:28:00 > 0:28:05In the meantime, it's just the ducks and us that are left behind
0:28:05 > 0:28:08to enjoy this beautiful and atmospheric observatory.
0:28:11 > 0:28:13We've had a great time here at Herstmonceux.
0:28:13 > 0:28:17It's been wonderful to see these lovely old telescopes.
0:28:17 > 0:28:19And when we come back next month, we'll be celebrating
0:28:19 > 0:28:22the summer solstice by launching our Moore Moon Marathon.
0:28:22 > 0:28:25We've selected some easy-to-find features on the moon
0:28:25 > 0:28:28for you to tick off during those warm summer nights.
0:28:28 > 0:28:29And so, until next month...
0:28:29 > 0:28:31ALL: Good night.
0:28:42 > 0:28:45Subtitles by Red Bee Media Ltd