0:00:34 > 0:00:35Good evening.
0:00:35 > 0:00:39In this very special programme, we're going to talk about something
0:00:39 > 0:00:44that won't happen again for over 100 years, so make the most of it -
0:00:44 > 0:00:47this is a transit of Venus.
0:00:47 > 0:00:50If you know, there are two planets closer to the sun than we are -
0:00:50 > 0:00:52Mercury and Venus.
0:00:52 > 0:00:54And when they pass in transit,
0:00:54 > 0:00:58you see them pass across the sun as black spots.
0:00:58 > 0:01:00The great astronomer, Copernicus,
0:01:00 > 0:01:02realised that the planets go round the sun.
0:01:02 > 0:01:07What he didn't know was how far away they were
0:01:07 > 0:01:09and what astronomers wanted to do was to measure
0:01:09 > 0:01:14the distance between the Earth and the sun, and that was far from easy.
0:01:14 > 0:01:17They had to wait for a transit of Venus.
0:01:17 > 0:01:20With seeing the last one, you couldn't see it well from here
0:01:20 > 0:01:23you could from the Arctic island of Svalbard
0:01:23 > 0:01:27and that's where three of our Sky At Night team went.
0:01:27 > 0:01:30So, over to Chris in Svalbard.
0:01:32 > 0:01:34The archipelago of Svalbard
0:01:34 > 0:01:37is a starkly glamorous part of the Arctic Circle.
0:01:37 > 0:01:4078 degrees north of the equator,
0:01:40 > 0:01:43home to eider ducks, polar bears
0:01:43 > 0:01:46and the town of Longyearbyen, it's a magical place.
0:01:47 > 0:01:49In winter, the sun never rises here
0:01:49 > 0:01:53but right now, in summer, the sun never sets.
0:01:55 > 0:01:59This is the land of the midnight sun, which is just as well,
0:01:59 > 0:02:01because we'll need that to see the whole transit.
0:02:01 > 0:02:04It begins just after midnight local time.
0:02:04 > 0:02:07The weather's not too bad for this part of the world.
0:02:07 > 0:02:10I really hope it stays clear because the next transit doesn't happen
0:02:10 > 0:02:15until the 22nd century, so this is really my last chance.
0:02:15 > 0:02:18I've never been this far north before.
0:02:18 > 0:02:21Svalbard is, after all, not that far from the North Pole.
0:02:21 > 0:02:23It's already been quite an adventure getting here.
0:02:23 > 0:02:28The sun remains at the same height above the horizon throughout the day,
0:02:28 > 0:02:31an effect that feels distinctly disorientating
0:02:31 > 0:02:33to those of us from more southerly climes.
0:02:35 > 0:02:40Lucie Green and Pete Lawrence have joined me on this quest.
0:02:40 > 0:02:43It's the night before the transit and we're going on a voyage with
0:02:43 > 0:02:47a team of European scientists who work on the Venus Express mission.
0:02:47 > 0:02:52Venus express has spent the last six years studying Earth's evil twin,
0:02:52 > 0:02:57trying to work out why Venus is quite so different from our own world.
0:02:59 > 0:03:02Amongst those trying to solve its mysteries is Colin Wilson,
0:03:02 > 0:03:06who helped set up this extraordinary trip.
0:03:06 > 0:03:09What's happening tomorrow is that Venus is going to pass
0:03:09 > 0:03:14directly in front of the sun and this is an incredibly rare event.
0:03:14 > 0:03:17It happens... The last one happened in 2004.
0:03:17 > 0:03:20The next one after this isn't going to happen until 2117.
0:03:20 > 0:03:23And also to illustrate how rare it is,
0:03:23 > 0:03:25the last ones before that weren't since the 19th century.
0:03:25 > 0:03:28It seems each generation of astronomers
0:03:28 > 0:03:32lucky enough to see a transit has their own reasons for observing it.
0:03:32 > 0:03:35For us in the 21st century,
0:03:35 > 0:03:37it's a chance to test methods we might use
0:03:37 > 0:03:42to study the atmospheres of planets which orbit other stars.
0:03:42 > 0:03:46Planetary transits are the only way we have of characterising exoplanets.
0:03:46 > 0:03:48These are planets discovered around other stars,
0:03:48 > 0:03:51of which we've discovered hundreds in the last decade.
0:03:51 > 0:03:53We've discovered them because, in some cases,
0:03:53 > 0:03:55- they go in front of their star? - Because of transits.
0:03:55 > 0:03:58But then once we know the planets are there,
0:03:58 > 0:04:00these exoplanets, we try to characterise them.
0:04:00 > 0:04:03We try to think, does it have water? Does it have oxygen?
0:04:03 > 0:04:05Could it be conceivably a nice place to live,
0:04:05 > 0:04:08or where someone may already live? And to study that,
0:04:08 > 0:04:11the only technique we have is planetary transits.
0:04:11 > 0:04:14Here, we have a very rare event which is
0:04:14 > 0:04:17a transit of an Earth-like planet in front of a sun-like star,
0:04:17 > 0:04:19and once we've done that analysis,
0:04:19 > 0:04:22we can actually look up the right answers,
0:04:22 > 0:04:26because satellites like Venus Express are giving us
0:04:26 > 0:04:28the detailed composition and we can tell
0:04:28 > 0:04:30whether the transit analysis has been right.
0:04:31 > 0:04:35Colin and his colleagues may be here for astronomical reasons,
0:04:35 > 0:04:37but the boat trip's also a chance
0:04:37 > 0:04:40to see the magnificent scenery of Svalbard and even spot some wildlife.
0:04:42 > 0:04:44There he is!
0:04:44 > 0:04:48Well, it's a beautiful evening up in Svalbard, a beautiful location.
0:04:48 > 0:04:51What do you reckon, Lucie - not a bad place for a transit?
0:04:51 > 0:04:53This is absolutely perfect.
0:04:53 > 0:04:56We've got fantastic clear skies at the moment, which bodes well
0:04:56 > 0:04:58and you know, it was quite a journey getting here,
0:04:58 > 0:05:00so I'm full of excitement
0:05:00 > 0:05:03and I can't wait to see how the sun looks in terms of the sunspots
0:05:03 > 0:05:06as well as seeing the black disc of Venus moving across as well.
0:05:06 > 0:05:08Of course, we're here
0:05:08 > 0:05:10because we need to see the sun just after midnight.
0:05:10 > 0:05:14The sun is up for the entire day and all night.
0:05:14 > 0:05:18It's 7:30 at night and the sun's still up there. It's pretty nice.
0:05:18 > 0:05:21- It sinks to about 10 degrees above the horizon.- That's right.
0:05:21 > 0:05:25Pete, you've been doing some careful observation of the conditions.
0:05:25 > 0:05:27What did you make of your day here so far?
0:05:27 > 0:05:31Well, in the morning, I was actually quite depressed about things
0:05:31 > 0:05:33because there was thick cloud everywhere
0:05:33 > 0:05:35and there was no wind, so nothing was moving.
0:05:35 > 0:05:39Then suddenly, as if by magic, it just disappeared completely.
0:05:39 > 0:05:43I got the telescope out, tested the telescope and I actually managed
0:05:43 > 0:05:45to find Venus, which is really close to the sun at the moment.
0:05:45 > 0:05:50We're not very many hours before the transit and I now feel at home.
0:05:50 > 0:05:54We also have to worry about seeing, about how crisp the sky is.
0:05:54 > 0:05:56I really wouldn't worry about that.
0:05:56 > 0:05:59The scene this afternoon was amazing. Venus was absolutely crisp.
0:05:59 > 0:06:01The atmosphere looks really, really steady,
0:06:01 > 0:06:05so long as the clouds stay away, and we've got no guarantee of that,
0:06:05 > 0:06:08but fingers crossed they do, we should have a fantastic view.
0:06:08 > 0:06:12- We're looking forward to the transit, you're looking forward to your sunspots.- Yeah.
0:06:12 > 0:06:14You've got some work to do before the transit, Pete,
0:06:14 > 0:06:17you've got some images you want to get before Venus hits the sun?
0:06:17 > 0:06:20I'd really like to try and get Venus about a degree and a half
0:06:20 > 0:06:24away from the sun, which is really, really close.
0:06:24 > 0:06:30That's probably about 24-30 hours before the transit actually starts.
0:06:30 > 0:06:34If I hit it right, what happens is,
0:06:34 > 0:06:36where Venus looks like a crescent...
0:06:36 > 0:06:40It's a crescent when it's further round and then as it gets closer...
0:06:40 > 0:06:43..as it gets closer, the cusps of the crescent start to elongate round.
0:06:43 > 0:06:44If you get it at the right point,
0:06:44 > 0:06:47which is dangerously close to the sun, those cusps join up
0:06:47 > 0:06:50and you get a ring, which I'm really looking forward to seeing.
0:06:50 > 0:06:53This is light being refracted in the atmosphere of Venus.
0:06:53 > 0:06:55It's scattered round the upper part of the atmosphere.
0:06:55 > 0:06:59- It's just creating this amazing ring effect.- I'm looking forward to it.
0:06:59 > 0:07:02Tonight, I'm going to enjoy the boat trip, see a bit of Svalbard,
0:07:02 > 0:07:05and our surroundings and if the weather's like this tomorrow,
0:07:05 > 0:07:08then I will be deeply, deeply happy.
0:07:08 > 0:07:11I think I'll be happy too.
0:07:11 > 0:07:14We're not the first to travel for a transit of Venus.
0:07:14 > 0:07:18Previous generations have scrambled to the far ends of the globe
0:07:18 > 0:07:20whenever these rare events come round.
0:07:22 > 0:07:26We've just come to a grinding halt. We've hit some ice.
0:07:26 > 0:07:29Feels appropriate, given the hardships and struggles
0:07:29 > 0:07:31that the previous transit expeditions went through.
0:07:34 > 0:07:36Our boat journey comes to an end
0:07:36 > 0:07:38exactly 24 hours before the transit,
0:07:38 > 0:07:42with brilliantly clear midnight sunlit skies
0:07:42 > 0:07:45making Longyearbyen look rather tranquil.
0:07:45 > 0:07:47I feel rather less calm, it has to be said.
0:07:47 > 0:07:51We need these clear skies to last until tomorrow.
0:07:53 > 0:07:57This will be only the seventh transit of Venus ever observed
0:07:57 > 0:07:59and the reason transits are so rare
0:07:59 > 0:08:02stand to a little bit of celestial mechanics.
0:08:07 > 0:08:09To get a transit we need the sun, Venus and Earth
0:08:09 > 0:08:11to be exactly in a straight line.
0:08:11 > 0:08:15That doesn't happen every day. It needs a special set of circumstances.
0:08:15 > 0:08:17The solar system is dynamic
0:08:17 > 0:08:20and Venus, being much closer to the sun than the Earth is,
0:08:20 > 0:08:25orbits more rapidly, taking only 225 days to do one lap.
0:08:27 > 0:08:30Whereas I over here for the Earth take, of course,
0:08:30 > 0:08:32a whole year to go round.
0:08:32 > 0:08:36In fact, I only catch up with the Earth after 584 days.
0:08:36 > 0:08:41And you'd think that there'd be a transit every 584 days?
0:08:41 > 0:08:43But that's not actually what happens.
0:08:43 > 0:08:46When we look at the orbits of Venus and the Earth
0:08:46 > 0:08:48we see that they're tilted with respect to each other
0:08:48 > 0:08:50by just over three degrees
0:08:50 > 0:08:55and that means that even when this alignment happens, sometimes
0:08:55 > 0:08:59Venus passes underneath the sun from the Earth's perspective
0:08:59 > 0:09:04and at other times, it's moving above the sun from the Earth's perspective.
0:09:04 > 0:09:07In that case, a transit doesn't happen.
0:09:07 > 0:09:10So all of this only comes together very, very rarely.
0:09:10 > 0:09:13In fact it happens twice, eight years apart,
0:09:13 > 0:09:15separated by a gap of more than a century,
0:09:15 > 0:09:19so that's why we have to wait so long for the next transit of Venus.
0:09:20 > 0:09:24By the 18th century, astronomers were making incredible efforts
0:09:24 > 0:09:27to trace transits of Venus.
0:09:27 > 0:09:31Their aim was to get observations of the transit from all over the world.
0:09:31 > 0:09:34One famous expedition was led by Captain Cook,
0:09:34 > 0:09:37and they observed the transit from Tahiti in 1769
0:09:37 > 0:09:41before they ran into Australia on their way home.
0:09:41 > 0:09:43By timing how long it took for the planet Venus
0:09:43 > 0:09:45to pass in front of the sun, astronomers realised
0:09:45 > 0:09:49they could measure the sun's distance from the Earth.
0:09:50 > 0:09:53Observing the transit was therefore a high scientific priority,
0:09:53 > 0:09:57but once mixed in with efforts to improve navigation,
0:09:57 > 0:10:00it also became a matter of national prestige
0:10:00 > 0:10:02as scientists to persuaded
0:10:02 > 0:10:04governments and navies to lend them a hand
0:10:04 > 0:10:06as well as plenty of funding.
0:10:06 > 0:10:09Lucie and I took a trip up the hill overlooking Longyearbyen
0:10:09 > 0:10:14to talk about the successes and the failures of previous transit expeditions.
0:10:14 > 0:10:17I feel like we've had quite a trek coming up this beautiful mountain.
0:10:17 > 0:10:19Really, it's nothing compared to
0:10:19 > 0:10:22the lengths that the previous transit expeditions went to.
0:10:22 > 0:10:26I think we've done pretty well. We've come all the way up to the Arctic.
0:10:26 > 0:10:27You're quite right, of course.
0:10:27 > 0:10:31Particularly the 18th century transits, when they were trying to use
0:10:31 > 0:10:33the transit of Venus to measure the solar system.
0:10:33 > 0:10:36They sent observers right across northern Europe
0:10:36 > 0:10:39to try and get as many observations as possible.
0:10:39 > 0:10:41For example, the Swedish Academy of Sciences
0:10:41 > 0:10:43sent people up to northern Sweden.
0:10:43 > 0:10:46The French Academy of Sciences, who were behind a lot of the efforts
0:10:46 > 0:10:49to try and co-ordinate these observations
0:10:49 > 0:10:52sent somebody off to the Russian Siberian wastes
0:10:52 > 0:10:55and he had a particularly terrible time, because it was spring
0:10:55 > 0:10:58and he was trying to get to his observing site as everything melted
0:10:58 > 0:11:01and of course, that's not very good if you're travelling by sled.
0:11:01 > 0:11:04And so, he ended up having to get his local crew drunk to get them to
0:11:04 > 0:11:09go across the last of the rivers with the ice cracking underneath them.
0:11:09 > 0:11:12But he made it and so we have observations from Siberia,
0:11:12 > 0:11:14observations from northern Sweden.
0:11:14 > 0:11:18What we don't have and we really needed were observations from India.
0:11:18 > 0:11:21In particular, there was a Frenchman called Le Gentil.
0:11:21 > 0:11:24Ah, the unluckiest astronomer of all time!
0:11:24 > 0:11:27He is. He set off in 1760 to see the 1761 transit.
0:11:27 > 0:11:29He gets attacked by the British.
0:11:29 > 0:11:32The world was at war at that point, it was the Seven Years War.
0:11:32 > 0:11:34They only escaped because of fog.
0:11:34 > 0:11:38He makes it to Madagascar, doesn't make it to Pondicherry,
0:11:38 > 0:11:40the French colony in India because of the war.
0:11:40 > 0:11:42In fact, the British have taken it.
0:11:42 > 0:11:45And so, he ends up on serving the transit of Venus from the deck
0:11:45 > 0:11:47of a ship, really rather poorly.
0:11:47 > 0:11:49Which of course would be moving all the time.
0:11:49 > 0:11:52Exactly - no good for precision observations.
0:11:52 > 0:11:55But also, they need to know where on the Earth they are
0:11:55 > 0:11:58and he can't get good measurements as to where the ship is.
0:11:58 > 0:12:00And so, he decides, quite sensibly,
0:12:00 > 0:12:03that instead of going all the way back to France,
0:12:03 > 0:12:05he's going to hang around for the 1769 transit.
0:12:05 > 0:12:06He waited for eight years,
0:12:06 > 0:12:09which when you go to those lengths, I suppose you might as well do.
0:12:09 > 0:12:13The whole month before the transit was beautifully clear.
0:12:13 > 0:12:15Gets up every morning and it's clear skies
0:12:15 > 0:12:17and then on the morning of the transit,
0:12:17 > 0:12:20he writes in his journal that he woke up about two in the morning,
0:12:20 > 0:12:22he could hear the wind whipping in off the sea
0:12:22 > 0:12:25and he knew that that meant clear whether.
0:12:25 > 0:12:27But, as you know, he wandered outside and looked up
0:12:27 > 0:12:29and it was completely overcast.
0:12:29 > 0:12:32And then he comes back and describes throwing himself face down
0:12:32 > 0:12:37onto the bed and he writes, "Such is the fate of astronomers."
0:12:37 > 0:12:39And in fact, he went mad.
0:12:39 > 0:12:40It is amazing to think that at the time
0:12:40 > 0:12:43when we didn't know the size of the solar system,
0:12:43 > 0:12:47we also didn't understand the Earth, we didn't have a map of the landmass
0:12:47 > 0:12:50and even know how to get accurate positions on the Earth.
0:12:50 > 0:12:53They did get observations, particularly 1769,
0:12:53 > 0:12:54from all over the place.
0:12:54 > 0:12:59It turns out one of the limiting factors that stopped them getting a perfect measurement
0:12:59 > 0:13:02was the fact they didn't know the distance between Greenwich and Paris.
0:13:02 > 0:13:05Some observers reported where they were relative to Paris,
0:13:05 > 0:13:07some relative to Greenwich,
0:13:07 > 0:13:09and that fundamental measurement wasn't made till much later.
0:13:09 > 0:13:12Of course, you needed to know the separation
0:13:12 > 0:13:15to put that into the calculation for the sun-Earth distance.
0:13:15 > 0:13:17Absolutely. Without that, then all of this effort,
0:13:17 > 0:13:20all of this trekking round the world is wasted.
0:13:20 > 0:13:23Then there's also the other thing that affected them,
0:13:23 > 0:13:26- which is this black drop affect... - The problems of the transit.
0:13:26 > 0:13:29That's right, this elongation of Venus when it's inside the sun,
0:13:29 > 0:13:31which means making the measurements,
0:13:31 > 0:13:34the crucial timing measurement, is incredibly difficult.
0:13:34 > 0:13:36We know from Halley that you need to get a measurement to within about
0:13:36 > 0:13:41one second of time in accuracy to get a good sun-Earth distance.
0:13:41 > 0:13:45The interesting thing is if you took what we know about the Earth now,
0:13:45 > 0:13:47we know the distance between Greenwich and Paris
0:13:47 > 0:13:49and we know where the observers were,
0:13:49 > 0:13:51if you take the measurements they made and that knowledge,
0:13:51 > 0:13:54you get a pretty good value for the distance to the sun.
0:13:54 > 0:13:55The best ones were within 1%
0:13:55 > 0:13:58of what we know as the sun-Earth distance now, which is incredible.
0:13:58 > 0:14:00- Good going.- Incredible, that's right.
0:14:00 > 0:14:05This is only the seventh transit to be witnessed by humanity,
0:14:05 > 0:14:08but we've come so far from working out the size of the solar system
0:14:08 > 0:14:11to looking for life elsewhere in our universe.
0:14:11 > 0:14:14Well, first of all, let's hope we see it.
0:14:15 > 0:14:19Well, I'm beginning to understand just how Le Gentil must have felt,
0:14:19 > 0:14:22because the clouds have rolled in.
0:14:22 > 0:14:26The sun is now completely obscured, leaving us more than a little worried
0:14:26 > 0:14:28about the forecast for tomorrow's transit.
0:14:28 > 0:14:32Inspired by the plucky astronomers of the 18th and 19th centuries,
0:14:32 > 0:14:36we could do nothing but grit our teeth and hope for the best.
0:14:37 > 0:14:39While we wait for the skies to clear,
0:14:39 > 0:14:43we've set up our very own transit up here in the snow.
0:14:43 > 0:14:46Transits occur whenever there are three bodies in a row.
0:14:46 > 0:14:49So we've got the Earth, we've got a purple ping-pong ball
0:14:49 > 0:14:52pretending to be Venus, and then of course, we've got the sun back here.
0:14:52 > 0:14:56But what you see during a transit depends on exactly where you are.
0:14:56 > 0:14:58The observers on the Earth
0:14:58 > 0:15:01experienced an affect known as parallax,
0:15:01 > 0:15:04which means that observers near the North Pole
0:15:04 > 0:15:06see Venus in one position against the disc of the sun
0:15:06 > 0:15:09but you'll notice that towards the South,
0:15:09 > 0:15:14Venus appears in a different place against the face of the sun.
0:15:14 > 0:15:17And so with that measurement, they only needed to know one more thing -
0:15:17 > 0:15:20they needed to know the relative distance from the sun, out here,
0:15:20 > 0:15:25to Venus and then from Venus back to the Earth.
0:15:25 > 0:15:28And that's something that had been known since the 1600s
0:15:28 > 0:15:30thanks to the work of Kepler, who realised that
0:15:30 > 0:15:34the orbits of the planets around the sun had a special relationship
0:15:34 > 0:15:37- to how far each planet was from the sun.- And so that was it.
0:15:37 > 0:15:40With those two measurements, the speed the planets were moving
0:15:40 > 0:15:44and the observations of the transits, the observers were able to set out
0:15:44 > 0:15:48the scale of the solar system for the very first time.
0:15:50 > 0:15:54There are only two planets which transit the sun as seen from Earth -
0:15:54 > 0:15:55Venus and Mercury.
0:15:55 > 0:16:00Let's go back to Patrick to hear more about these two enigmatic worlds.
0:16:03 > 0:16:05Time now to talk about the inner solar system.
0:16:05 > 0:16:09With me are Chris North and Paul Abel.
0:16:09 > 0:16:15These planets are very different, so let's begin with little Mercury.
0:16:15 > 0:16:18Yes, I have it here. The usual sky at night model..
0:16:18 > 0:16:20Wonderful little Mercury.
0:16:20 > 0:16:24In fact, Mercury, one of the ancient planets known since antiquity,
0:16:24 > 0:16:28earliest cavemen must have seen it whizzing around in the sky.
0:16:28 > 0:16:31We had to wait till the start of the telescopic area before we could
0:16:31 > 0:16:33begin making investigations of it.
0:16:33 > 0:16:35Even then, we didn't see an awful lot.
0:16:35 > 0:16:38- We didn't really know much until the space age?- That's right.
0:16:38 > 0:16:41The reason being, of course, Mercury's very small
0:16:41 > 0:16:43and it's very close to the sun,
0:16:43 > 0:16:45and this makes it very difficult to observe.
0:16:45 > 0:16:48Schiaparelli, of course, made lots of observations of it.
0:16:48 > 0:16:52We had to wait until, was it Mariner 10 got out to Mercury first?
0:16:52 > 0:16:56Yes, Mariner 10 went round it, passed it by the 1970s,
0:16:56 > 0:16:59made the first observations. One of the problems with Mercury is that
0:16:59 > 0:17:02it's so close to the sun that if we send a spacecraft there from Earth,
0:17:02 > 0:17:04it's a third of the distance from the sun
0:17:04 > 0:17:06and as the spacecraft goes inwards,
0:17:06 > 0:17:09it gets faster and faster and faster,
0:17:09 > 0:17:11which means that it whizzes past Mercury,
0:17:11 > 0:17:14so the biggest problem with going into orbit around Mercury
0:17:14 > 0:17:16- is actually slowing down enough. - Yes.
0:17:16 > 0:17:20So the Messenger spacecraft had a very convoluted journey
0:17:20 > 0:17:22to actually end up going into orbit around Mercury
0:17:22 > 0:17:24and is the first spaceship ever to go into orbit.
0:17:24 > 0:17:28Everything else, Mariner 10, just passed straight by.
0:17:28 > 0:17:34So, up next then, the planet Venus. Now, this is an interesting world.
0:17:34 > 0:17:37It couldn't be more further removed from Mercury.
0:17:37 > 0:17:41Shrouded with a very thick, poisonous atmosphere. Lovely, bright object.
0:17:41 > 0:17:45It's a beauty. Go there, you'll find it anything but beautiful.
0:17:45 > 0:17:46Indeed. It's more like hell.
0:17:46 > 0:17:49It's an interesting planet for observers to look at.
0:17:49 > 0:17:53It's very, very bright and the reason it's very bright is because
0:17:53 > 0:17:55the vast clouds covering it reflect a lot of sunlight.
0:17:55 > 0:17:59This means that the early telescopic observers that looked at Venus
0:17:59 > 0:18:01didn't see an awful lot,
0:18:01 > 0:18:04so Venus became a mystery. I think we had to wait again till
0:18:04 > 0:18:07the spacecraft got there, because there was very little we could do.
0:18:07 > 0:18:11With the space age, we've had probes that have actually gone to Venus.
0:18:11 > 0:18:13The earlier probes were squashed on the way down?
0:18:13 > 0:18:16- They were, yes. - They didn't make it to the surface.
0:18:16 > 0:18:18The pressure on the surface of Venus
0:18:18 > 0:18:21is 90 times the pressure on the surface of Earth,
0:18:21 > 0:18:23so they had to build the spacecraft again
0:18:23 > 0:18:25to try and survive the pressures. They got to the surface
0:18:25 > 0:18:29and discovered the temperature on the surface is 400 degrees.
0:18:29 > 0:18:31The longest a probe survived on the surface was
0:18:31 > 0:18:34Venera 13 in the 1980s, I think.
0:18:34 > 0:18:36That sent back that lovely image, one of my favourite ones,
0:18:36 > 0:18:38a little bit of glowing sky.
0:18:38 > 0:18:41That lasted for 127 minutes, that's just over two hours.
0:18:41 > 0:18:43Finally, its electronics overheated.
0:18:43 > 0:18:47- I think we can forgive it for that. - Well, yes!
0:18:47 > 0:18:50- I wouldn't like to survive in that kind of in environment. - No, I wouldn't.
0:18:50 > 0:18:53To make it worse, the atmosphere is very dense, the surface is very hot,
0:18:53 > 0:18:57and you have sulphuric acid clouds to contend with.
0:18:57 > 0:19:02We've had probes go there, so we had the Magellan probe in 1990,
0:19:02 > 0:19:05which made a radar map using radar that can penetrate
0:19:05 > 0:19:07the very thick clouds
0:19:07 > 0:19:11and was able to map the surface and show us mountains,
0:19:11 > 0:19:14volcanoes, in fact, possibly or probably not active,
0:19:14 > 0:19:16certainly not very many of them active,
0:19:16 > 0:19:20and valleys and so on and lava flows.
0:19:20 > 0:19:23Very interesting structures on the surface as well.
0:19:23 > 0:19:27There are sort of pancake shapes, a very, very weird surface.
0:19:27 > 0:19:29All kinds of volcanoes.
0:19:29 > 0:19:32Yes, it's a very volatile world on the surface to look at
0:19:32 > 0:19:35and it helps that the maps are always drawn in that sort of
0:19:35 > 0:19:38orangey-yellow colour, which makes it look very hot.
0:19:38 > 0:19:41Whether any of the volcanoes are active now,
0:19:41 > 0:19:43well that's a matter for debate.
0:19:43 > 0:19:45- A great debate.- It is.
0:19:45 > 0:19:47We know that a few hundred million years ago,
0:19:47 > 0:19:50there was an enormous resurfacing of the surface of the planet
0:19:50 > 0:19:55due to this immense bout of volcanism which plagued the surface,
0:19:55 > 0:19:59and it's possible that Venus undergoes such bouts, you know,
0:19:59 > 0:20:02- in periodic cycles. - It would certainly explain why
0:20:02 > 0:20:05the surface appears to be all the same age.
0:20:05 > 0:20:07It's actually all very young. If we try and count the craters
0:20:07 > 0:20:10on the surface of Venus, we actually see there are very few,
0:20:10 > 0:20:11only about 1000 on the entire surface.
0:20:11 > 0:20:14And over a whole planet, that's not very many at all.
0:20:14 > 0:20:17Partly that's because it's been resurfaced and partly
0:20:17 > 0:20:21because the atmosphere burns up the smaller objects that hit it.
0:20:21 > 0:20:24Both Mercury and Venus are inferior planets, they are closer to
0:20:24 > 0:20:28the sun than we are, and from our point of view, occasionally
0:20:28 > 0:20:31they pass in front of the sun in an event known as a transit.
0:20:31 > 0:20:35The best place to study the sun is in fact from the very
0:20:35 > 0:20:38northern climes of Europe, in Svalbard.
0:20:38 > 0:20:41And the team, Chris, Lucy and Pete, have been there.
0:20:41 > 0:20:45So, back now to Svalbard.
0:20:45 > 0:20:49'The Sky At Night team has come to the Arctic Circle to see
0:20:49 > 0:20:53'the transit of Venus, which is happening later tonight.'
0:20:53 > 0:20:55Down in Longyearbyen, Peter has been on an expedition
0:20:55 > 0:20:58to find a good spot to observe the sun
0:20:58 > 0:21:02and get an elusive shot of Venus as it approaches it.
0:21:02 > 0:21:05Well, I brought lots and lots of kit over from the UK
0:21:05 > 0:21:08to see the transit of Venus from Svalbard.
0:21:08 > 0:21:14Now, the transit is going to occur in a number of hours' time,
0:21:14 > 0:21:18but before that actually happens, there are other things to look at.
0:21:18 > 0:21:22I have been following Venus over the last few days from the UK
0:21:22 > 0:21:25and watching that beautiful, slender crescent get thinner
0:21:25 > 0:21:27and thinner and thinner.
0:21:27 > 0:21:29Now, as it gets really close to the sun,
0:21:29 > 0:21:32the cusps of the present begin to extend around and
0:21:32 > 0:21:35if I am really lucky and if I can find it today, I might be able to
0:21:35 > 0:21:39see them join up to create a ring, which is the atmosphere of Venus.
0:21:39 > 0:21:41Now, that should be really quite special,
0:21:41 > 0:21:43so I'm really very excited about that.
0:21:43 > 0:21:46Venus guards its secrets well.
0:21:46 > 0:21:53In a telescope, it looks so lovely, mysterious and welcoming.
0:21:53 > 0:21:55But its thick, impenetrable atmosphere
0:21:55 > 0:21:58is full of carbon dioxide and sulphuric acid,
0:21:58 > 0:22:00a most uninviting world.
0:22:01 > 0:22:03Venus and Earth are almost the same size,
0:22:03 > 0:22:06but that is where the similarities end.
0:22:06 > 0:22:10It rotates much more slowly and spins backwards.
0:22:10 > 0:22:12It also lacks a magnetic field.
0:22:13 > 0:22:16Earth's magnetic field protects us from damaging particles
0:22:16 > 0:22:22from the sun and from space, and a nice bonus is the Aurora Borealis.
0:22:23 > 0:22:27In winter, Svalbard is a great place to see the Northern Lights.
0:22:27 > 0:22:31It is a sign that the magnetic field above is acting as our shield.
0:22:34 > 0:22:36What I have here is a magnet
0:22:36 > 0:22:40with a north magnetic pole and a south magnetic pole
0:22:40 > 0:22:43and iron filings around the magnet, so if you look carefully,
0:22:43 > 0:22:45you can see that the iron filings
0:22:45 > 0:22:48take on what is actually the shape of the magnetic field
0:22:48 > 0:22:51and they form these beautiful arches going from one pole to the other.
0:22:51 > 0:22:54You can see here, they're in arcs, right?
0:22:54 > 0:22:55So, this is a pretty good model
0:22:55 > 0:22:58- of the Earth's magnetic field. - That's right.
0:22:58 > 0:22:59And it's nice, because this is three-dimensional
0:22:59 > 0:23:03so you can see the magnetic field forms a sphere
0:23:03 > 0:23:06and the magnetic field lines shown by the iron filings
0:23:06 > 0:23:09go in at the north pole
0:23:09 > 0:23:12and the south pole, which is what we have happening around us here,
0:23:12 > 0:23:15for the huge Earth's magnetic field.
0:23:15 > 0:23:17If this is inside Earth, we're here in this
0:23:17 > 0:23:20- cluster of iron filings at the top, near the poles.- That's right.
0:23:20 > 0:23:23So, this is the shape of the Earth's magnetic field,
0:23:23 > 0:23:27- sitting in the solar system. - So, when you have the solar wind,
0:23:27 > 0:23:29those particles coming in towards this, they get channelled
0:23:29 > 0:23:32down towards the poles, that's how you get the Northern Lights.
0:23:32 > 0:23:35That's right, and it becomes very clear to see why that's the case.
0:23:35 > 0:23:39The particles coming from the sun can get on to
0:23:39 > 0:23:41the Earth's magnetic field lines, and if they do that,
0:23:41 > 0:23:45they can be funnelled down, and they naturally get funnelled to the
0:23:45 > 0:23:49polar regions because that is where the magnetic field is guiding them,
0:23:49 > 0:23:53the field acts as this kind of tube, along which the particles can flow.
0:23:53 > 0:23:57So, here on the Earth, this invisible magnetic field above
0:23:57 > 0:24:02our heads protects us from the solar wind and that is really important.
0:24:02 > 0:24:06But on Venus, there is no protection at all.
0:24:06 > 0:24:09Without a magnetic field, Venus has no way to stop the solar
0:24:09 > 0:24:15wind from constantly bombarding it, stripping away its atmosphere.
0:24:15 > 0:24:19We think that billions of years ago, Venus was once a wet world.
0:24:19 > 0:24:21'And Dr Janet Luhmann talked to me about why
0:24:21 > 0:24:25'she thinks the lovely Venus became the Earth's evil twin.'
0:24:26 > 0:24:28Well, Venus is special
0:24:28 > 0:24:32and different than the Earth in that it does not have
0:24:32 > 0:24:35an internal magnetic field.
0:24:35 > 0:24:40And so, there is nothing to prevent the solar wind from directly
0:24:40 > 0:24:44- entering the upper atmosphere. - Slammed straight into it.
0:24:44 > 0:24:46Slammed straight into it like a comet,
0:24:46 > 0:24:50and a very long time ago, science fiction writers
0:24:50 > 0:24:54thought Venus was a very large comet and presented it as such.
0:24:54 > 0:24:58When we finally visited Venus with spacecraft
0:24:58 > 0:25:01and took detailed measurements, we of course proved
0:25:01 > 0:25:06to ourselves once and for all that Venus is very much a planet.
0:25:06 > 0:25:12One of the things that has been a puzzle is the lack of water on Venus.
0:25:12 > 0:25:14And what happened to it in the past.
0:25:14 > 0:25:18So assuming Venus began in a very similar state to the Earth.
0:25:18 > 0:25:20Exactly.
0:25:20 > 0:25:24Whereas Earth in its oceans has in the order of a kilometre
0:25:24 > 0:25:27equivalent of water if you spread the oceans over the globe,
0:25:27 > 0:25:33on Venus there is only a few microns of water in the atmosphere.
0:25:33 > 0:25:38And so, that and the particular composition of hydrogen
0:25:38 > 0:25:40in Venus's atmosphere, which is unusual,
0:25:40 > 0:25:46combined with the oxygen loss that we see, suggests maybe water has been
0:25:46 > 0:25:49stripped off the top of the atmosphere
0:25:49 > 0:25:53over the 4.5 billion year lifetime of the solar system.
0:25:53 > 0:25:58The main question is whether it occurred in a much stronger
0:25:58 > 0:26:01fashion early in the solar system's history.
0:26:01 > 0:26:03It feels like Venus has been overlooked in recent years,
0:26:03 > 0:26:06it has become the evil twin or the ugly sister.
0:26:06 > 0:26:10But actually, there is still a lot of exciting things to find out.
0:26:10 > 0:26:14Exactly. And in fact, it is the twin Earth,
0:26:14 > 0:26:20from early observations of its similarity in size,
0:26:20 > 0:26:23and it is the most proximate planet, it's closest to us.
0:26:23 > 0:26:25And yet, all our attention has been
0:26:25 > 0:26:29focused on Mars, in part because we can actually go to Mars
0:26:29 > 0:26:31and rove on the surface
0:26:31 > 0:26:35and photograph it in minute detail, in all wavelengths, essentially.
0:26:35 > 0:26:39On Venus, we have this shrouded body,
0:26:39 > 0:26:44with incredible pressures on the surface that would crush most
0:26:44 > 0:26:49equipment and of course would be totally unfriendly
0:26:49 > 0:26:53and inhospitable to anything resembling life as we know it.
0:26:53 > 0:26:56And now, it is good to see that there is some attention
0:26:56 > 0:26:59being refocused on Venus.
0:26:59 > 0:27:02In space, the LASCO telescope is looking at the sun
0:27:02 > 0:27:06and we can see Venus marching towards its edge.
0:27:06 > 0:27:09Just as it was getting dangerously close,
0:27:09 > 0:27:12Pete did manage to get his Venusian ring,
0:27:12 > 0:27:16created by sunlight being deflected off the top of the atmosphere.
0:27:16 > 0:27:18It's really rather beautiful.
0:27:24 > 0:27:26It's 11 o'clock at night here in Svalbard,
0:27:26 > 0:27:29the transit of Venus festivities have begun.
0:27:29 > 0:27:32It is still light, as you can see, which is great.
0:27:32 > 0:27:34It's also pretty cloudy, which isn't.
0:27:34 > 0:27:36There are a few breaks in the clouds, though,
0:27:36 > 0:27:38so we haven't given up hope yet.
0:27:38 > 0:27:40But whatever happens, in about an hour from now,
0:27:40 > 0:27:43the last transit of Venus of the 21st century will have begun,
0:27:43 > 0:27:46whether we are able to see it or not.
0:27:46 > 0:27:48Most of Svalbard is here
0:27:48 > 0:27:53and the locals are getting into the spirit of the occasion.
0:27:53 > 0:27:54The longer we are here,
0:27:54 > 0:27:59the more I begin to sense what life in this frontier land must be like.
0:27:59 > 0:28:02Previous explorers who have travelled to see the transit of Venus
0:28:02 > 0:28:05found all sorts of things, so I pretty much imagine this is what
0:28:05 > 0:28:09those arctic explorers encountered, back in the 18th century.
0:28:09 > 0:28:13THEY SING IN NORWEGIAN
0:28:13 > 0:28:19What I have here is the low-tech way of watching the transit of Venus.
0:28:19 > 0:28:21This is a simple solar viewer.
0:28:21 > 0:28:25The light comes in through the glass at the front, bounces off some
0:28:25 > 0:28:29mirrors on the inside and then down through a lens and it projects
0:28:29 > 0:28:33an image of the sun a few inches across on a piece of paper in here.
0:28:33 > 0:28:36So this is a really simple and really safe way to
0:28:36 > 0:28:38look at the transit of Venus, and I should be able to see
0:28:38 > 0:28:41the event happening really clearly with this piece of kit.
0:28:41 > 0:28:44But also, using this, I can see sunspots
0:28:44 > 0:28:46that are on the surface of the sun.
0:28:46 > 0:28:48And I know at the moment, there are some really fantastic
0:28:48 > 0:28:51sunspot groups, so I'm looking forward to seeing
0:28:51 > 0:28:53just how close Venus gets to those.
0:28:55 > 0:28:58The skies are still ominously heavy, but Miguel and Michelle
0:28:58 > 0:29:02from the European Space Agency have set up their telescopes nonetheless.
0:29:02 > 0:29:07They will be sending images of the transit live onto the web.
0:29:07 > 0:29:09But only if those clouds clear.
0:29:09 > 0:29:12Also here are the Venus Twilight Experiment,
0:29:12 > 0:29:17a global collaboration in the best tradition of transit hunting,
0:29:17 > 0:29:20with teams in Japan, in Hawaii, in Kazakhstan
0:29:20 > 0:29:23and even in Ulan Bator in Mongolia.
0:29:23 > 0:29:26All of these teams are waiting to catch something called
0:29:26 > 0:29:30the arc of Venus, or more scientifically, the aureole.
0:29:30 > 0:29:34It occurs when the sun's light is seen shining directly through
0:29:34 > 0:29:38the thick Venusian atmosphere, rather than being reflected by it.
0:29:39 > 0:29:44And it occurs for just a few fleeting seconds, around the beginning
0:29:44 > 0:29:46and the end of the transit.
0:29:46 > 0:29:49There will be a sort of ring of light around Venus,
0:29:49 > 0:29:51which is fantastic to see.
0:29:51 > 0:29:57We have great expectations of how beautiful this should be.
0:29:57 > 0:30:02It is mostly visible during what we call the first contact,
0:30:02 > 0:30:05which is when Venus hits the sun, and the second contact,
0:30:05 > 0:30:08when Venus is now fully plunged into the face of the sun.
0:30:08 > 0:30:10So, it is a matter of 15 to 20 minutes.
0:30:10 > 0:30:15The arc of Venus was seen during the 2004 transit,
0:30:15 > 0:30:19both from the trace spacecraft and by amateur astronomers on the ground.
0:30:19 > 0:30:23Remarkably, we can even see detail in the arc,
0:30:23 > 0:30:26revealing the layers of Venus's atmosphere.
0:30:26 > 0:30:30In 1882, there were only visual and some photography,
0:30:30 > 0:30:34but the photography did not see the aureole.
0:30:34 > 0:30:38Only drawings by expert observers mentioned this aureole.
0:30:38 > 0:30:40It was also mentioned in the 18th century,
0:30:40 > 0:30:43even since 1761 and 1769.
0:30:43 > 0:30:46The telescope works by blocking out the sun
0:30:46 > 0:30:50so that the delicate arc of light can be revealed.
0:30:50 > 0:30:52But setting it up in Svalbard has been tricky.
0:30:52 > 0:30:54We wanted to observe from here
0:30:54 > 0:30:56because this is the only part of Europe that can actually see
0:30:56 > 0:30:59both ends of the transit - the ingress,
0:30:59 > 0:31:03when Venus comes into the sun, and the egress, which is the opposite.
0:31:03 > 0:31:07And for that, we had to use portable equipment, because there is
0:31:07 > 0:31:11no major astronomical facility here, no fixed facility.
0:31:11 > 0:31:15And this is also something which is difficult for any astronomer,
0:31:15 > 0:31:19to align a portable motorised mount.
0:31:19 > 0:31:23You always need to aim at the pole in a very accurate manner,
0:31:23 > 0:31:25and this is the midnight sun period of the year,
0:31:25 > 0:31:28so there are no stars at all, so this is difficult to do.
0:31:28 > 0:31:30It's nice to see that the French
0:31:30 > 0:31:33and the British can set up next to each other without war breaking out!
0:31:33 > 0:31:36A little bit different from the 18th century.
0:31:36 > 0:31:38But we do still share some problems with that
0:31:38 > 0:31:41unluckiest of astronomers, Le Gentil.
0:31:41 > 0:31:44After all, the thick clouds are still hanging about
0:31:44 > 0:31:46and time is beginning to run out.
0:31:48 > 0:31:51Look, I'm not a natural optimist. But that looks much like it did
0:31:51 > 0:31:55just before we got that clear patch, half an hour ago.
0:31:55 > 0:32:00- Well, if it does go, it's going to be a real rush.- I think that's...
0:32:00 > 0:32:02Do you see what I mean? I think that's breaking,
0:32:02 > 0:32:04in between the different bands.
0:32:04 > 0:32:07We might just get a crack. That's all we need.
0:32:07 > 0:32:10I don't actually know where the sun is up there at the moment,
0:32:10 > 0:32:14but those rays in the distance, they are pointing back to it.
0:32:14 > 0:32:18- That's right... Really? Has it moved all the way round?- It has, yeah.
0:32:18 > 0:32:21- We'll be waiting a while. - I'm probably wrong, then.
0:32:21 > 0:32:24It's so bizarre, because we're now coming up to midnight,
0:32:24 > 0:32:26and it's daylight.
0:32:26 > 0:32:29- It is, which is good. - For a transit, it's excellent!
0:32:29 > 0:32:32This is the thing, for transit of Venus explorers,
0:32:32 > 0:32:36we are in the right place at the right time, with our equipment.
0:32:36 > 0:32:39- Well, we can't control the weather. - We can't.
0:32:39 > 0:32:45The transit will be a long affair, lasting nearly 7 hours.
0:32:45 > 0:32:46But the beginning and end are dramatic.
0:32:46 > 0:32:50The tension is running high.
0:32:50 > 0:32:53Getting another glimpse of the sun coming out.
0:32:53 > 0:32:55But not the full disc.
0:32:55 > 0:32:58Will it be enough for Pete to get his telescopes lined up?
0:32:58 > 0:33:00I don't think so.
0:33:03 > 0:33:05It's such a tease!
0:33:09 > 0:33:11Lucy, you were telling me that you wanted to see something
0:33:11 > 0:33:14called the black drop, which you only see on the way in and out?
0:33:14 > 0:33:17That's right, this elongation of the disc of Venus
0:33:17 > 0:33:20when it's close to the edge of the sun. Since the last transit,
0:33:20 > 0:33:23people have put forward an explanation for that.
0:33:23 > 0:33:25I want to see it myself, and then later on see
0:33:25 > 0:33:28- other people's opinions. - The sun is right there, isn't it?
0:33:30 > 0:33:33We've got a few minutes to go, come on!
0:33:33 > 0:33:35We've flown all this way, we've brought all this kit.
0:33:35 > 0:33:37It could do it, actually.
0:33:37 > 0:33:40I'm going to change tack, I'm going to go to white light now.
0:33:40 > 0:33:42- OK.- And have a look. I'm going for it.
0:33:42 > 0:33:45- Do we need to get out of your way, Pete?- No, you're fine there.
0:33:45 > 0:33:48Patrick tells a story of an eclipse in Finland where
0:33:48 > 0:33:50he was the only person to leave his kit.
0:33:50 > 0:33:53- I know, and he was the only one that got the picture.- Yes.
0:33:53 > 0:33:55You've got to be optimistic, haven't you?
0:33:55 > 0:33:57You just don't know what the cloud is going to do.
0:33:57 > 0:34:00- No, it's just thin enough to give us a little bit of hope.- Yeah.
0:34:00 > 0:34:03And this telescope will track the sun?
0:34:03 > 0:34:07- It will, if I can find the sun first!- Once we're locked on.
0:34:07 > 0:34:10Well, somebody locally predicted the clouds would clear at midnight.
0:34:10 > 0:34:12But also, according to Ian,
0:34:12 > 0:34:14they were sitting on their porch with a beer
0:34:14 > 0:34:19- when they predicted that, so... - That can make you more optimistic!
0:34:19 > 0:34:22'This is astronomical torture. Goodness knows how those
0:34:22 > 0:34:27'who had staked their career on transit observing must have felt.'
0:34:27 > 0:34:31- Well, about two minutes left. - It's not looking good.
0:34:31 > 0:34:35It's not, my optimism was there for a second, it's faded already.
0:34:35 > 0:34:37Mine peaked for about 30 seconds, now it's gone.
0:34:37 > 0:34:40There's a higher level of cloud that's come in that wasn't there,
0:34:40 > 0:34:42literally wasn't there half an hour ago.
0:34:42 > 0:34:45It's really grey. Really, really grey.
0:34:45 > 0:34:48The sun is just there, near that gap in the clouds.
0:34:48 > 0:34:52- We've got the telescope, so we just need...- Oh, is that the sun's...
0:34:52 > 0:34:56- No, it's not the sun's disc, is it? Is it?- Is it?
0:34:56 > 0:34:58That could... No, it's too far over.
0:34:59 > 0:35:01- Yes, it is.- I'll go with anything.
0:35:01 > 0:35:03- Yes, it is, it is.- It's too round.
0:35:03 > 0:35:06Is it? Yes, it is. There's the sun.
0:35:06 > 0:35:08Pete, well spotted. Two minutes to go.
0:35:08 > 0:35:12- OK.- This would just be the most magical piece of timing.
0:35:12 > 0:35:14- Come on!- Oh, my goodness, come on!
0:35:14 > 0:35:17It's not bright enough to register through the filter.
0:35:17 > 0:35:19- A minute and a half to go. - It's about to brighten, Pete.
0:35:19 > 0:35:22- We've got the top bit as well. - Is that where it is?
0:35:22 > 0:35:25Yeah, it comes in across the top.
0:35:25 > 0:35:29< PEOPLE SHOUT You're already aligned. I think some people over there have got it.
0:35:29 > 0:35:32Literally 20 seconds and the sun's just come out.
0:35:32 > 0:35:35I think some people over there have got it. We've heard some gasps.
0:35:35 > 0:35:39We can see the sun. Can Pete get his telescope on it, though? That's the question.
0:35:39 > 0:35:42- It's going to disappear again. - Oh, come on!
0:35:44 > 0:35:47SHE SPEAKS IN FRENCH
0:35:47 > 0:35:51'A clear patch in the right place at the right time
0:35:51 > 0:35:54'and Pete gets his first shot of the transit of Venus.'
0:35:54 > 0:35:58Pete, I can't quite believe we've got this, and I won't distract you too much,
0:35:58 > 0:36:02but just at the point where Venus started crossing the sun,
0:36:02 > 0:36:04we've got a clear patch
0:36:04 > 0:36:09and there is the last chance you'll have for 105 years
0:36:09 > 0:36:12to see Venus beginning to cross the face of the sun.
0:36:12 > 0:36:16Even though the clouds are there, it still sends tingles up the back of your neck.
0:36:16 > 0:36:20- It's dramatic with the clouds going past.- Yeah, definitely.
0:36:20 > 0:36:22Proof that the solar system is working.
0:36:22 > 0:36:24There's a sunspot in the top-left as well.
0:36:24 > 0:36:26There are loads of sunspots on there
0:36:26 > 0:36:28which is quite photogenic. It's like the sun is a canvas
0:36:28 > 0:36:31against which the transit is taking place.
0:36:31 > 0:36:34- That's very nice. - Yeah, I thought so, too.
0:36:34 > 0:36:37'Venus has begun its long crawl across the sun's disc,
0:36:37 > 0:36:42'a majestic demonstration of the power of celestial mechanics,
0:36:42 > 0:36:45'but we are still at the mercy of nature.'
0:36:45 > 0:36:48If the clouds weren't here, we should be seeing Venus now,
0:36:48 > 0:36:51just passing over the edge of the sun.
0:36:51 > 0:36:54We've had first contact, and in a few minutes' time,
0:36:54 > 0:36:55we'll have second contact,
0:36:55 > 0:36:58- so maybe we'll catch that one. - Lucie!
0:36:58 > 0:37:02- We've got it!- Oh, I'm missing it!
0:37:02 > 0:37:04It's actually behind some thick cloud.
0:37:04 > 0:37:06- It's just about there. - Oh, yes, there it is!
0:37:06 > 0:37:09- It's moving quite quickly onto the disc, isn't it?- Wow!
0:37:09 > 0:37:12- Incredibly fast. - It's maybe halfway there now.
0:37:12 > 0:37:13My goodness...
0:37:13 > 0:37:16So we've got ten minutes now until second contact?
0:37:16 > 0:37:19- That's right. When Venus is completely on the sun. - Fully inside, that's right.
0:37:19 > 0:37:23We can see if we can see the infamous black drop.
0:37:23 > 0:37:26- It's very black at the minute. - It doesn't exist.
0:37:26 > 0:37:30'Previous observers reported that something strange happens
0:37:30 > 0:37:32'as Venus moves onto the sun's disc.
0:37:32 > 0:37:36'It seems to stretch, forming the infamous black drop.
0:37:36 > 0:37:39'We'll have to wait and see if the black drop is real.
0:37:39 > 0:37:41'For now, I'm with Pete, a sceptic.'
0:37:41 > 0:37:44It's like if you hold your finger and thumb up
0:37:44 > 0:37:47and you have them close to you. As you put them closer together,
0:37:47 > 0:37:50it looks like your finger and thumb begin to join together.
0:37:50 > 0:37:53- Yeah.- That's one theory. - And in bad optics.
0:37:53 > 0:37:56- Yeah.- You've got a little layer of heat between your finger and thumb,
0:37:56 > 0:37:58and I think that distorts the view.
0:37:58 > 0:38:01Yes!
0:38:01 > 0:38:03Everyone is just ecstatic
0:38:03 > 0:38:06that after our long wait, we're finally getting a glimpse of Venus.
0:38:06 > 0:38:11These are some of the first views from spacecraft looking at the sun.
0:38:11 > 0:38:14In these amazing time-lapse movies,
0:38:14 > 0:38:18we see Venus entering the sun's disc, with all its dramatic texture,
0:38:18 > 0:38:22in breathtaking detail. It's both beautiful and astounding.
0:38:29 > 0:38:31The transit's officially started now.
0:38:31 > 0:38:34We can actually see it from Svalbard.
0:38:34 > 0:38:37Only an hour late, but that's pretty good!
0:38:37 > 0:38:40Look at that! Isn't that spectacular?
0:38:40 > 0:38:43That big black circle.
0:38:43 > 0:38:47- It's so clear.- Have you seen this?! It's got all the ridges in it.
0:38:47 > 0:38:49It does.
0:38:49 > 0:38:53You can see the disc really clearly. It looks terrific.
0:38:53 > 0:38:57It's really clearly defined.
0:38:57 > 0:38:59'It's touch and go at the minute - one moment the sun's there
0:38:59 > 0:39:03'and then it's gone, but we've still seen it.'
0:39:03 > 0:39:05I think we should settle in for the night, guys,
0:39:05 > 0:39:09- cos that's gone behind a very large bank of cloud.- Definitely.
0:39:09 > 0:39:12So, transit is underway. We saw some of it,
0:39:12 > 0:39:15so mission accomplished, as far as I'm concerned,
0:39:15 > 0:39:19- and now everything else is just gravy, don't you think? - Yeah, definitely.
0:39:21 > 0:39:24Gentlemen, how is it for you? How's it going?
0:39:24 > 0:39:26- It was stressy...- Stressy, yeah!
0:39:26 > 0:39:29..because we can do nothing automatically,
0:39:29 > 0:39:32- so we have to do it manually. - Because of the clouds? - Because of the clouds.
0:39:32 > 0:39:35This means that we have to adjust the cameras, the setup,
0:39:35 > 0:39:37for every shot.
0:39:37 > 0:39:41- But you've managed to see something? - Yes, and it's so exciting!
0:39:41 > 0:39:43We had to take the filter out, in fact,
0:39:43 > 0:39:48so that we could see the image of the sun
0:39:48 > 0:39:51through the clouds. So the cloud was the filter.
0:39:51 > 0:39:53'Looking at the sun is incredibly dangerous,
0:39:53 > 0:39:57'so do always use filters or project its image
0:39:57 > 0:39:59'and be very careful with the telescope.'
0:39:59 > 0:40:02How are you doing so far? Have you seen anything?
0:40:02 > 0:40:05Well, I saw quite a nice view in the beginning,
0:40:05 > 0:40:08for a glimpse of both the sun and Venus,
0:40:08 > 0:40:11and then we had some clouds.
0:40:11 > 0:40:14I swapped the eyepiece to the camera and I made some shots.
0:40:14 > 0:40:16I think I got a couple of good things.
0:40:16 > 0:40:19- So you've seen the transit?- I've seen part of it.- Mission accomplished.
0:40:19 > 0:40:22It's going great. We've got the live feeds from the guys here,
0:40:22 > 0:40:25and also their colleagues in Canberra,
0:40:25 > 0:40:27which we're keeping an eye on.
0:40:27 > 0:40:30- Clear weather in Canberra, by the look of it.- There's some cloud, too,
0:40:30 > 0:40:32- but there's Venus down there. - Excellent.
0:40:32 > 0:40:35I've just taken a nice shot of the transit
0:40:35 > 0:40:37through our ESA TV cameras there.
0:40:37 > 0:40:40- Very good.- We've got a video camera there as well.
0:40:40 > 0:40:43- And going straight out on Twitter? - Yeah, and retweeted around the world.
0:40:43 > 0:40:48That's probably a first. This is live tweeting of a transit for the first time in history.
0:40:48 > 0:40:51- That's probably right. That's amazing.- There are always firsts.
0:40:51 > 0:40:54'Some news from the Twilight team -
0:40:54 > 0:40:57'no luck in Svalbard,
0:40:57 > 0:41:00'but they've heard from Arizona that there's been a successful observation
0:41:00 > 0:41:03'of the arc of Venus.'
0:41:03 > 0:41:08The report I just received says that they observed the aureola very well.
0:41:08 > 0:41:11It was quite bright, very asymmetrical, as expected.
0:41:11 > 0:41:14Which is what you wanted, cos that's the interest.
0:41:14 > 0:41:18And it was more intense near the pole.
0:41:18 > 0:41:22Moreover, it was also observed well before the first contact...
0:41:22 > 0:41:25- Oh, great.- ..which means we'll have a long photometric curve
0:41:25 > 0:41:28on each of the points on the Venus atmosphere.
0:41:28 > 0:41:30This is what we want
0:41:30 > 0:41:34because the longer the light curve is for each point,
0:41:34 > 0:41:37the best constraint we have on the temperature
0:41:37 > 0:41:40- at the point we try to measure. - Ulan Bator? Have you heard from them?
0:41:40 > 0:41:43No, but I think they don't have fast internet there,
0:41:43 > 0:41:45so I don't expect them to call during the transit.
0:41:48 > 0:41:52So we've got the sunspots that we can see really clearly.
0:41:52 > 0:41:54- Oh, yeah.- A variety of sizes
0:41:54 > 0:41:57and a real cluster of them, actually.
0:41:57 > 0:41:59- There's an enormous number there. - Yup.
0:41:59 > 0:42:03I can see the umbra and the penumbra of some of those ones.
0:42:03 > 0:42:05- The faint shadow around the sunspot? - That's right.
0:42:05 > 0:42:08And then Venus, of course, with no penumbra,
0:42:08 > 0:42:10just the big black dot moving across the face of the sun.
0:42:10 > 0:42:13Isn't that a fantastic sight? Venus is just so perfect.
0:42:13 > 0:42:18- Lucie, you should get your solarscope out.- It's bright enough now.
0:42:18 > 0:42:23Finally we've got a shadow on here that I can use
0:42:23 > 0:42:25to align it. Now...
0:42:25 > 0:42:28There we go! Look, there's Venus
0:42:28 > 0:42:31and one, two, three, four, five, six sunspots, maybe?
0:42:31 > 0:42:33Fantastic!
0:42:33 > 0:42:36And what I like about this Sunspotter is that
0:42:36 > 0:42:38because the Earth is rotating so fast,
0:42:38 > 0:42:41the sun is moving out of the field of view of my Sunspotter
0:42:41 > 0:42:44so I'm always having to make an adjustment every few minutes.
0:42:44 > 0:42:46It'd be much easier if the Earth didn't rotate!
0:42:46 > 0:42:50- Working out the sun-Earth distance would be much easier.- That's true!
0:42:53 > 0:42:56So, here we can see Venus
0:42:56 > 0:42:58looking pretty much like a very large sunspot
0:42:58 > 0:43:02- with no penumbra, with no light around the edge. - It looks darker than the sunspots.
0:43:02 > 0:43:05- Maybe it's just larger. - Yeah, much, much larger.
0:43:05 > 0:43:08It's great to see it in such a simple... No offence to your Sunspotter,
0:43:08 > 0:43:10but in such a simple device. That's full sunshine.
0:43:10 > 0:43:13- Yeah.- Let's look. Have you seen it with the naked eye yet?
0:43:13 > 0:43:17- No, I haven't given that a go. - Let's see if we can see this.- OK.
0:43:17 > 0:43:20Oh, yeah. There it is. I can see it.
0:43:20 > 0:43:22That's rather nice.
0:43:22 > 0:43:25- There's a band of cloud that looks rather pretty.- It does.
0:43:28 > 0:43:31It's about one-thirtieth of the width of the sun,
0:43:31 > 0:43:35and I was worried that my eyes wouldn't be good enough to pick it out, but there it is.
0:43:35 > 0:43:39All we need now is the rest of the clouds to go away.
0:43:39 > 0:43:42'The sun is always changing
0:43:42 > 0:43:46'and one type of feature that comes and goes is the sunspots.
0:43:46 > 0:43:48'These can be bigger than the Earth
0:43:48 > 0:43:50'and they're cool areas on the surface.
0:43:50 > 0:43:53'Right now, there's a group of sunspots
0:43:53 > 0:43:55'and also something called a "filament"
0:43:55 > 0:43:58'where the sun's magnetic energy is holding up gas.'
0:43:59 > 0:44:05I'm trying to see Venus with a hydrogen-alpha filter.
0:44:05 > 0:44:08The sun is so bright that it makes it difficult to see
0:44:08 > 0:44:12any detail on your computer screen.
0:44:12 > 0:44:16But with my patented black shroud,
0:44:16 > 0:44:21which got a lot of interest from some of the locals yesterday,
0:44:21 > 0:44:25it helps me to see the detail. There's the sunspot group
0:44:25 > 0:44:28and there is a giant, twisting filament,
0:44:28 > 0:44:31a dark, snaking line, if you like,
0:44:31 > 0:44:34running between all the sunspots there.
0:44:34 > 0:44:36So that makes quite a pretty picture.
0:44:36 > 0:44:39'I study the sun every day
0:44:39 > 0:44:42'using spacecraft that look at it in different ways.
0:44:42 > 0:44:45'Each wavelength tells you something different.'
0:44:47 > 0:44:51One thing I wanted to ask you, Lucie. Pete's been imaging in hydrogen-alpha
0:44:51 > 0:44:55so what exactly is that and what are we seeing in these H-alpha images?
0:44:55 > 0:44:59In hydrogen-alpha, this is a narrow part of the visible spectrum
0:44:59 > 0:45:01that the filter allows through,
0:45:01 > 0:45:04and it's a really useful part of the spectrum to use
0:45:04 > 0:45:05because it sees not the lowest part
0:45:05 > 0:45:08of the sun's atmosphere - the photosphere.
0:45:08 > 0:45:10That's the bit we normally see in most of the images?
0:45:10 > 0:45:13Right. So when you see sunspots, it's normally the photosphere,
0:45:13 > 0:45:17but the hydrogen-alpha sees a layer of the atmosphere slightly higher,
0:45:17 > 0:45:19a layer that we call the chromosphere,
0:45:19 > 0:45:21and this is the red layer that you see
0:45:21 > 0:45:24- during a total eclipse.- And what you pick up is the activity on the sun.
0:45:24 > 0:45:27I noticed in one of Pete's images, as Venus moved across,
0:45:27 > 0:45:31- you had what looked like squiggly lines just above it.- Yeah.
0:45:31 > 0:45:34- Are those the filaments?- That's right. These are the filaments.
0:45:34 > 0:45:37- They look like snakes on the surface of the sun.- Yeah.
0:45:37 > 0:45:39When you see them at the edge, we call them prominences.
0:45:39 > 0:45:41- When they stick out?- That's right.
0:45:41 > 0:45:43But they're exactly the same thing.
0:45:43 > 0:45:48They are relatively cool gas that's held up in the sun's atmosphere a little bit higher,
0:45:48 > 0:45:50and I was really pleased to see
0:45:50 > 0:45:52that there's a really nice S-shaped one
0:45:52 > 0:45:55on the sun at the moment. There's a dispersed sunspot group
0:45:55 > 0:45:57- that we were looking at in white light.- I saw that.
0:45:57 > 0:46:00When we moved up and looked in the hydrogen-alpha filter,
0:46:00 > 0:46:03we saw not really the sunspots so much,
0:46:03 > 0:46:07but we saw the filament that was also in that sunspot group.
0:46:07 > 0:46:11So then we start to go up into the atmosphere, which is fairly hot.
0:46:11 > 0:46:14It goes from 6,000 degrees centigrade at the surface,
0:46:14 > 0:46:17up into millions in the atmosphere,
0:46:17 > 0:46:19and you're right, that's what we start to see from space.
0:46:19 > 0:46:22We start to look in ultraviolet light, extreme ultraviolet light,
0:46:22 > 0:46:24and then even X-rays coming from the hot atmosphere.
0:46:24 > 0:46:27Some of the satellites saw the transit before we did,
0:46:27 > 0:46:31- cos they see Venus going through the sun's atmosphere.- That's right.
0:46:31 > 0:46:35Yeah, so now is a really nice era to have a transit of Venus,
0:46:35 > 0:46:37because you're making use of the light
0:46:37 > 0:46:39all across the electromagnetic spectrum.
0:46:39 > 0:46:41There's going to be some fantastic images that come through.
0:46:41 > 0:46:44It is magical, being here and seeing it the old-fashioned way
0:46:44 > 0:46:47- and having the space-based images as well.- Yeah.
0:46:47 > 0:46:51'Colin has an ingenious arrangement
0:46:51 > 0:46:53'with which to view Venus,
0:46:53 > 0:46:56'and it's a safe way to look at the sun by projecting it.
0:46:56 > 0:46:58'The transit's really a rather special sight,
0:46:58 > 0:47:00'even at three in the morning.'
0:47:00 > 0:47:03This is something I borrowed from a colleague
0:47:03 > 0:47:06and it does look a bit like a pizza box.
0:47:06 > 0:47:09It is a bit of folded cardboard. You get quite a good image.
0:47:09 > 0:47:12Yeah, you've got the sunspots there, and Venus.
0:47:12 > 0:47:15- It must be about mid-transit, I would say.- Yeah. About mid-transit.
0:47:15 > 0:47:16Maybe just past.
0:47:16 > 0:47:19We didn't have this going for the beginning of the transit
0:47:19 > 0:47:23because we've had clouds, but now it's glorious, in fact.
0:47:23 > 0:47:25Yeah. It's good.
0:47:25 > 0:47:29So actually, what I meant to ask you, while we're sitting here mid-transit,
0:47:29 > 0:47:32is you are, of course, involved with Venus Express,
0:47:32 > 0:47:35which is going around Venus. What's it doing right now, do you think?
0:47:35 > 0:47:37Will it be making observations during the transit?
0:47:37 > 0:47:41Yeah. It's got a 24-hour orbit, which is convenient,
0:47:41 > 0:47:43so we know exactly where it is in its orbit.
0:47:43 > 0:47:46At this time of day, in fact, around three in the morning,
0:47:46 > 0:47:49is usually when it comes its closest to Venus.
0:47:49 > 0:47:52It will be taking some particles and fields measurements,
0:47:52 > 0:47:55so it's got its magnetometer recording magnetic fields.
0:47:55 > 0:48:00It could be searching for lightning right now because we only
0:48:00 > 0:48:03are sensitive to that when we're within the magnetosheath.
0:48:03 > 0:48:07- When you're close in.- Yeah. - That's quite something.
0:48:07 > 0:48:10The dot down there that I can see is a planet the size of Earth
0:48:10 > 0:48:14and you're telling me there might well be storms.
0:48:14 > 0:48:17- Suddenly makes it feel real. - We've seen the signs of lightning.
0:48:17 > 0:48:22- I don't think you'll see flashes. - Not even if I look closely.- No, no.
0:48:22 > 0:48:24This transit is fun to watch,
0:48:24 > 0:48:30but astronomers are using transits to study planets orbiting other stars.
0:48:30 > 0:48:32Here we have an extraordinarily rare event.
0:48:32 > 0:48:37We have a transit of an earth-like planet in front of a familiar star
0:48:37 > 0:48:40and we can use all the transit analysis techniques on it.
0:48:40 > 0:48:45And we can try to study it. We can look for signs of habitability.
0:48:45 > 0:48:47And when we've done that analysis, we can see
0:48:47 > 0:48:51whether we were right because we know what Venus is like in detail
0:48:51 > 0:48:55because we've got a satellite there measuring it in great detail.
0:48:55 > 0:48:59So if we find that our transit calculations are giving us
0:48:59 > 0:49:02the right answers, that gives us a lot more confidence
0:49:02 > 0:49:05in our analysis of exoplanets and our search for earth-like planets.
0:49:05 > 0:49:07Venus is continuing its magnificent journey
0:49:07 > 0:49:11and is now more than halfway across the sun.
0:49:11 > 0:49:14Pete has been looking at it with a special telescope.
0:49:14 > 0:49:18By using filters, he can look at different layers of the sun.
0:49:18 > 0:49:21Seeing the calcium layer reveals hidden detail.
0:49:22 > 0:49:25Pete, you've been observing with the calcium filter.
0:49:25 > 0:49:28- Can I see some of your images? - Yeah, sure.
0:49:28 > 0:49:32I've sort of taken a whole sequence to try and get the entire disc on here,
0:49:32 > 0:49:35but with calcium filters like this...
0:49:35 > 0:49:37- This is the telescope that you were using.- Yeah.
0:49:37 > 0:49:43I sort of describe it like a super white light view.
0:49:43 > 0:49:46It's like you get a view using a normal white light filter,
0:49:46 > 0:49:48so you're looking at the surface of the sun,
0:49:48 > 0:49:52but it's plus because you see all the bright regions
0:49:52 > 0:49:55around the sunspots in the centre of the disc.
0:49:55 > 0:49:58It's just full of detail, it's absolutely gorgeous.
0:49:58 > 0:50:01I don't often look at the sun in this wavelength.
0:50:01 > 0:50:04I'm familiar with visible light and familiar with the hydrogen-alpha.
0:50:04 > 0:50:06Both of those I'd use in my research.
0:50:06 > 0:50:09But I'm keen to see how it looks.
0:50:09 > 0:50:12- We're looking at the chromosphere of the sun.- Yes.
0:50:12 > 0:50:15- Right at the bottom of it, is that right?- Right.
0:50:15 > 0:50:20So the emission can come from a variety of heights.
0:50:20 > 0:50:24And the sunspots appear dark, still, so I can see those really clearly.
0:50:24 > 0:50:28Yeah. But then you get this large granular network,
0:50:28 > 0:50:30which is the chromospheric network.
0:50:30 > 0:50:31That's right.
0:50:31 > 0:50:37So what we're able to see is actually created by magnetic fields.
0:50:37 > 0:50:40Where the magnetic fields are very strong, in the sunspots,
0:50:40 > 0:50:41you have dark features,
0:50:41 > 0:50:44which is the same as you have in the visible light.
0:50:44 > 0:50:48But then this bright, mottled structure, that's still formed
0:50:48 > 0:50:51by the presence of magnetic fields, but just weaker.
0:50:51 > 0:50:54What's been your favourite wavelength?
0:50:54 > 0:50:55Visible, calcium or hydrogen-alpha?
0:50:55 > 0:50:59That's an awful question to ask! I don't know.
0:50:59 > 0:51:02Once I've switched to one, I want to go back to another
0:51:02 > 0:51:04because they all have their merits.
0:51:04 > 0:51:08I think the white light looks fantastic.
0:51:08 > 0:51:12But the calcium, you get all that beautiful detail underneath Venus
0:51:12 > 0:51:14and moving across the disc.
0:51:14 > 0:51:18And in H-alpha, you get all those beautiful snaking magnetic features.
0:51:18 > 0:51:21- So my answer to your question is I don't know.- All of them.
0:51:21 > 0:51:23They're all lovely, yeah.
0:51:23 > 0:51:25As well as the transit,
0:51:25 > 0:51:28I've been enjoying my first experience of the midnight sun.
0:51:28 > 0:51:32It's weird to think that we've been up all night and it never got dark.
0:51:32 > 0:51:36Despite the fact, though, that the light hasn't changed, it is morning
0:51:36 > 0:51:39and we're all beginning to feel a bit of nightshift strain,
0:51:39 > 0:51:43but it's time to wake up because the end of the transit is approaching.
0:51:43 > 0:51:46We're not far off the black drop here, actually.
0:51:46 > 0:51:48This is Venus getting very close now.
0:51:48 > 0:51:50This would be the point where you were struggling
0:51:50 > 0:51:54if you were trying to measure the scale of the solar system.
0:51:54 > 0:51:57This would be the point, wouldn't it, when you were just trying to time...
0:51:57 > 0:51:59..things very precisely, yeah.
0:51:59 > 0:52:02It's really wobbling around in the atmosphere.
0:52:02 > 0:52:06- The atmosphere is very poor, yeah. - Really, really poor, but we're...
0:52:06 > 0:52:10- I think I can still see some...- Gap. - It's hard.- There you go.- That's it.
0:52:10 > 0:52:12- There's the black drop.- Yes!
0:52:12 > 0:52:17So it looks like a connection between the blackness of space
0:52:17 > 0:52:18and then, yeah...
0:52:18 > 0:52:21And that's caused here
0:52:21 > 0:52:24- because we've got such poor atmospheric conditions.- Yeah.
0:52:24 > 0:52:28That was third contact, so Venus is on its way off the disc of the sun
0:52:28 > 0:52:30and there really can't be much transit left.
0:52:35 > 0:52:38Right now we are in between the third and fourth contact.
0:52:42 > 0:52:47And it's really amazing. Astonishing that we are seeing this.
0:52:47 > 0:52:52We are lucky that the weather is now good for the final phase.
0:52:55 > 0:52:59As we reach the end of the transit, with Venus just about to move off
0:52:59 > 0:53:04the face of the sun, a reverential quietness has descended on Svalbard.
0:53:05 > 0:53:08- A few minutes to go. - Three minutes by my watch.
0:53:10 > 0:53:11Yep.
0:53:14 > 0:53:17- That's good enough.- Yeah, then rotate across, that's nice.
0:53:17 > 0:53:21You can just see it here. Just as we come up to fourth contact,
0:53:21 > 0:53:24it's just visible with Venus on the edge of the sun's limb.
0:53:24 > 0:53:28It's really going, isn't it? Even without the black drop, on this.
0:53:28 > 0:53:31If this was what you were using to make your measurements,
0:53:31 > 0:53:33say in the 17th century, has it gone?
0:53:33 > 0:53:37Has it not? It's coming and going because of the atmosphere.
0:53:37 > 0:53:39That's right, if you don't have really good conditions,
0:53:39 > 0:53:42- this becomes even harder. - That's right.
0:53:44 > 0:53:45Goodbye, Venus.
0:53:48 > 0:53:50Miguel and Michel cast their laptops aside
0:53:50 > 0:53:54to see those final moments through the telescope,
0:53:54 > 0:53:57just as their predecessors did centuries ago.
0:53:58 > 0:54:03- It's gone.- Yeah.- Quick, record the time! Record the time!- It's gone.
0:54:07 > 0:54:09So we think that's it.
0:54:09 > 0:54:12After hours of waiting for the skies to clear
0:54:12 > 0:54:18and then hours of watching Venus move very, very slowly across the disc,
0:54:18 > 0:54:21looking at the sun in different wavelength bands,
0:54:21 > 0:54:23seeing the sunspots, the filaments,
0:54:23 > 0:54:27it looks like Venus has finally gone from the face of the sun.
0:54:28 > 0:54:31- It's rather depressing. - I'm going to bed!
0:54:31 > 0:54:32THEY LAUGH
0:54:32 > 0:54:35You've been working hard, Pete, seriously.
0:54:35 > 0:54:38Venus has departed, the show is over,
0:54:38 > 0:54:41so let's see how everyone else got on.
0:54:41 > 0:54:45Well, Colin? It's all done. How was it?
0:54:45 > 0:54:49- It was good and bits of it were even sunny.- Yeah, especially the end.
0:54:49 > 0:54:52- Did you see third and fourth contact?- Yes, yes.
0:54:52 > 0:54:55Looking over various shoulders and trying to goad people
0:54:55 > 0:54:59into telling me exactly when they occurred. It was great fun.
0:54:59 > 0:55:02It's really difficult, isn't it, to judge that final...
0:55:02 > 0:55:04No wonder their timings were difficult.
0:55:04 > 0:55:07I found judging that third or fourth contact was really hard.
0:55:07 > 0:55:10We had a couple of people looking through very similar equipment
0:55:10 > 0:55:15and they disagreed by several... ten seconds, something like this?
0:55:15 > 0:55:17Or more. Whereas meanwhile,
0:55:17 > 0:55:21an observer on a different telescope was claiming 20 seconds out.
0:55:21 > 0:55:25I heard you say, we were over there, and I heard you say,
0:55:25 > 0:55:28"Has anyone seen fourth contact?"
0:55:28 > 0:55:33- We thought it was 30 seconds earlier, so we were ahead of you.- You see?
0:55:33 > 0:55:37If we were a set of observers who had been sent out by the Royal Astronomy Society...
0:55:37 > 0:55:39We'd be scrapping on the way home!
0:55:39 > 0:55:43And we'd have done a great disservice to the whole astronomy community.
0:55:43 > 0:55:45We'd have screwed up the universal measurements.
0:55:45 > 0:55:49Thank God they don't rely on us any more. Not you and I.
0:55:49 > 0:55:51Even though they've been up all night,
0:55:51 > 0:55:54everyone is still basking in the glow of a successful transit.
0:55:54 > 0:55:57We are happy that we could do it
0:55:57 > 0:56:01because this morning it didn't look as if it would be possible.
0:56:01 > 0:56:06- So I think it was worth coming here with all the equipment. - Definitely. Definitely.
0:56:06 > 0:56:07And I think we're quite happy.
0:56:07 > 0:56:11It was very rewarding that the sun finally shone for us
0:56:11 > 0:56:14at the end, after a long, long night.
0:56:16 > 0:56:20With clouds passing. Yeah, it was fantastic.
0:56:20 > 0:56:24The Venus Twilight Team, though, are still hard at work.
0:56:24 > 0:56:27This is the edge of the sun, which is perfectly covered
0:56:27 > 0:56:30by the cone, which is designed for that, actually.
0:56:30 > 0:56:34It's off-centre, it's not in the optical axis of the telescope.
0:56:34 > 0:56:38- This is what allows us to centre on Venus.- Sure.
0:56:38 > 0:56:41And so it's probably there, acquiring
0:56:41 > 0:56:45and being written in the form of a file.
0:56:45 > 0:56:49- This will be analysed later.- Get the data first, do the work later. - Absolutely.
0:56:49 > 0:56:52The good news is that Thomas saw the aureole,
0:56:52 > 0:56:56that beautiful, faint arc of light hanging in space.
0:56:56 > 0:56:59Australia, too, got this lovely view,
0:56:59 > 0:57:04although we still haven't heard from Ulan Bator and their elephant.
0:57:04 > 0:57:08Pete also managed to get a glimpse of the aureole, an impressive sight.
0:57:10 > 0:57:12On our Sky At Night Flickr site,
0:57:12 > 0:57:16we have lots of lovely images of Venus as it went across the sun.
0:57:16 > 0:57:20And they really show what a global experience this transit has been,
0:57:20 > 0:57:24with images from as far afield as the South China Seas and Argentina,
0:57:24 > 0:57:29and even some nice ones from the rather cloud-ridden UK.
0:57:29 > 0:57:33Our spacecraft above the clouds also got some great images
0:57:33 > 0:57:37and movies showing Venus flying across the sun.
0:57:37 > 0:57:40This one, from the Solar Dynamic Observatory,
0:57:40 > 0:57:44a very special event finished in the blink of an eye.
0:57:44 > 0:57:47Well, the transit is over in a brilliant blue sky
0:57:47 > 0:57:50and I'm feeling a little odd right now.
0:57:50 > 0:57:53I've always known there'd be a transit of Venus in 2012,
0:57:53 > 0:57:56and now it's over, and I'll never see another one.
0:57:56 > 0:57:58That feels pretty strange.
0:57:58 > 0:58:00On the other hand, we came somewhere spectacular,
0:58:00 > 0:58:04with some remarkable people, and we saw an amazing sight.
0:58:04 > 0:58:05That feels pretty special.
0:58:25 > 0:58:30What a magnificent sight. And I do hope you saw the transit of Venus.
0:58:30 > 0:58:33If not, look on the Sky At Night website.
0:58:33 > 0:58:35When I come back next month,
0:58:35 > 0:58:39we'll be talking about small amateur observatories.
0:58:39 > 0:58:41Until then, good night.
0:58:58 > 0:58:59Subtitles by Red Bee Media Ltd