The latest discoveries reveal the mysterious and ever-changing nature of the Sun. Astronomers are only now beginning to understand the vast power of our giant star, and new ground-breaking investigations show it like never before.
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LearningTranscript
00:0590 million miles from us lies the greatest power in the solar system.
00:11It lights our lives and warms our world.
00:17The sun.
00:20For most of us, our sun remains a mystery.
00:24Too bright to look at with the naked eye.
00:28But we're going to show you our star as you've never seen it before.
00:39Oh, my goodness.
00:43We'll discover what the latest science is revealing about our very own star.
00:49From the extraordinary drama of a total eclipse
00:53to the magical beauty of the northern lights.
00:58We'll be exploring the sun's most spectacular displays
01:02and what they can tell us about its inner workings.
01:06We'll investigate the sun's changing nature,
01:09its dramatic cycles of activity.
01:13Is it coming our way or not? And if so, how fast?
01:16And the unexpected effects these cycles can have on our lives.
01:24The sun is more active now than it has been for a decade.
01:28And a new generation of satellites is capturing it in more detail than ever before.
01:36Come explore how new science is revealing the secret history of the sun.
01:58To begin to understand the sun's extraordinary power,
02:02and its changing cycles of activity.
02:05We need the help of one of the most dramatic events in the astronomical calendar.
02:11A total solar eclipse.
02:25November 2012.
02:28Cairns, Australia.
02:31In 48 hours, there's going to be a total eclipse,
02:35and people have come from across the globe to catch it.
02:39But this one's special because it promises to reveal something crucial about what's going on with our sun.
02:49To get an eclipse, the moon must drift between the sun and the earth.
02:55At what's called first contact, the moon begins to block it.
03:00But what's extraordinary is what happens when the sun is completely covered.
03:05That moment of totality reveals something that's normally hidden by the sun's glare.
03:11The sun's faint atmosphere.
03:14The corona.
03:15And it's the corona that's key to what this eclipse can tell us.
03:23We're very lucky.
03:27The Earth is the only planet in the solar system from where you can witness a total eclipse.
03:33Because although the moon is 400 times smaller than the sun, it's also 400 times closer.
03:41So at a total eclipse, it appears to be exactly the same size.
03:49There's a total eclipse on average every 18 months.
03:53So they're not exactly rare.
03:55But catching one isn't easy.
04:00The narrow shadow paths they trace on the Earth's surface are far more likely to pass over uninhabited regions, such
04:07as the oceans, than a populated area like Cairns.
04:13And the timing of this eclipse is significant.
04:18Right now, we're due to be at solar maximum.
04:22The period of greatest activity in the sun's cycle.
04:27But each maximum is slightly different.
04:31So scientists need to confirm that we've actually reached it.
04:41Just click on that.
04:45Delivery!
04:47One way to confirm solar maximum is to study the sun's corona during totality.
04:54It's what makes this eclipse especially exciting.
04:57Even to the most hardened eclipse chasers.
05:09Astronomer Francisco Diego has seen 17 total eclipses.
05:15This time, he's advising a group of 100 British enthusiasts.
05:19But he's also brought his own equipment.
05:23A camera and some filters are all Francisco needs to take photographs of the corona.
05:29It's the shape of the corona in the photos that will show him if we're at solar maximum.
05:36The shape of the solar corona is modulated by magnetic fields on the sun,
05:42which in turn are the consequence of an 11-year cycle.
05:46So this 11-year cycle of activity in the sun goes to very high activity, low activity, and then high
05:52again.
05:52And in that process, the shape of the solar corona is changing all the time.
05:56For example, when the corona is very round, that means the solar activity is at the maximum.
06:03You have a lot of myths and legends about the disappearance of the sun in the middle of the day.
06:06And still today, I think we have that fear.
06:09When we see that shadow coming, it comes at twice the speed of the sun, very, very fast,
06:14and covers the whole landscape in a matter of a couple of minutes.
06:17And it is terrifying. And we still feel that.
06:19I mean, you're operating your equipment, and you still feel that fear and that anxiety of the sun disappearing in
06:25the middle of the day.
06:26So, in a way, yes, it will be one of the reasons that we travel to those remote places to
06:33witness and to feel this very deep emotion,
06:38this link that we have with nature, with natural phenomenon.
06:44Francisco will only have two minutes in which to get a successful picture of the corona.
06:515 a.m., the day of the eclipse. The sun is already rising.
06:57First contact is only ten minutes away.
07:08Oh, yeah. We're well on our way.
07:15The moon has begun to cover the sun.
07:18But the sun is so bright that there is no noticeable darkening of the daylight until much closer to totality.
07:31From now on, there is something strange in the light.
07:36You see, the colours are fading.
07:51What do you think, Francisco? It's looking quite skinny now.
07:54It's quite skinny. It's about ten minutes before totality.
07:57So this is where things are going to happen faster and faster.
07:59The darkness is going to really come much quicker.
08:08The darkness is going to really come much quicker.
08:17Oh, my goodness.
08:21The most amazing thing.
08:26I can't believe how beautiful it is.
08:31The moon has completely blocked the disk of the sun.
08:35A delicate halo is all that remains.
08:38It's the corona.
08:42Francisco now has two minutes and two seconds to get the photos he needs.
08:49Here it comes.
08:58Isn't that amazing?
09:02Amazing.
09:06It was great.
09:12The whole thing is over.
09:14And you are left with this image, as I have right now in my mind.
09:19The image of the solar corona there in that bit of the landscape.
09:23It's very, very intense, very fast.
09:26And you want to relax and to feel what you just saw.
09:33But what do Francisco's photos show?
09:36Has the sun reached its peak of activity?
09:53Astronomer Francisco Diego is trying to determine what stage the sun is in in its 11-year cycle.
10:01This is Francisco's photograph of the corona at a past solar minimum.
10:06The corona has a vertical axis.
10:09It is ordered and calm.
10:13But this is his 2012 Australian eclipse photo.
10:18The corona goes out in all directions.
10:21It's the sun at its most active, solar maximum.
10:29So why does the sun go through these cycles of activity?
10:37To understand why there is a solar cycle at all, we need to know what's going on deep within the
10:43sun.
10:45It's a place we can never go to.
10:50But we can learn a lot from something that makes the journey all the way from the core of the
10:55sun to us, here on Earth.
10:59Sunlight.
11:06We think of sunlight as simply coming from the sun's surface.
11:11But its journey is far more epic.
11:15It starts deep inside the sun, a vast burning mass of hydrogen and helium.
11:25It's the sun's enormous mass that creates the conditions to produce sunlight.
11:31Its intense gravitational pull forces the sun into layers, each with its own special properties.
11:40Beneath the thin outer peel is a 125,000-mile thick layer where hot material rises and falls.
11:48The next layer radiates the sun's heat outwards.
11:54And at around 250,000 miles is the core.
11:59A 16-million-degree furnace where the entire mass of the sun pushes inwards.
12:05The pressure is so vast that the very atoms are fused together.
12:14And it's that fusion reaction between atoms of hydrogen that gives birth to the sun's heat and light.
12:30The scientists here at the National Ignition Facility in California are trying to make a tiny sun and thus recreate
12:38fusion.
12:43Fusion in the sun's core keeps itself going, powered only by the sun's mass.
12:48Copying that here on Earth is not easy.
12:54All of this is about getting ignition that could change the world.
12:58Here in this dust-free environment, Beth Zanidis creates hydrogen fuel capsules smaller than a grain of rice,
13:06and destined for a very violent fate.
13:09This is called the capsule fill tube assembly.
13:12It's a 2-millimeter diameter plastic capsule.
13:16192 laser beams converge on the capsule,
13:19and that plastic material flows away from the capsule when it gets hot and under high pressure.
13:25And that causes a subsequent reaction of the fuel layer to be compressed so that the hydrogen atoms fuse.
13:35To get those atoms to fuse, they need to generate similar pressures to the sun's core.
13:42340 billion times the pressure on Earth.
13:45It's not easy, but there is a way.
13:54The 192 individual laser beams they use are each more powerful than any other laser on the planet.
14:03And they all fire at a spherical chamber at the heart of the complex.
14:09This is the target chamber.
14:12And when the lasers hit the fuel capsule at its center, they bring the atoms together with the same force
14:18as in the sun's core.
14:21But to truly mimic our star, the NIF team needs to pull off an even greater trick.
14:29Proceeding to system shot countdown state.
14:32Once ignited, that fusion reaction must keep itself going.
14:44Starting system shot sequence on my mark.
14:46Three, two, one, mark.
14:52May I have your attention?
14:55Preparations for shot operations in Laser Bay 2 are underway.
14:59Leave Laser Bay 2 now.
15:03It's not without its dangers.
15:05Before every shot, the area is evacuated.
15:09Three-foot-thick steel and concrete doors enclose the target chamber.
15:13A misfire from the most powerful laser in the world could cause a catastrophic explosion.
15:20MOR ready for system shot countdown clock.
15:23And even the smallest fusion reaction unleashes a lethal blast of neutrons and high energy light.
15:30Three, two, one.
15:39The only visible sign is this flash from the world's biggest laser as it fires.
15:48But inside that fuel capsule, they're hoping to create their tiny sun.
15:54And with it, man-made sunlight.
16:15Another day, another shot at creating nuclear fusion.
16:19The NIF team routinely achieve momentary fusion.
16:23But this time, no self-sustaining fusion.
16:26Yet if we could achieve it on Earth, we'd have the sun's energy at our fingertips.
16:34Recreating a small sun in this target chamber that's not too far away is always daunting in a lot of
16:41respects.
16:42We will get there eventually.
16:47It's that elusive trick of generating endless energy that makes our sun so miraculous.
16:55The result is the birth of sunlight in the sun's core in particles of light energy known as photons.
17:09But their journey is far from over.
17:14Imagine this pinball is a photon newly created in the sun's core.
17:19That light must now reach the sun's surface.
17:24But it's a very difficult journey.
17:26Because in between the core of the sun and the surface, there is a seething mass of superheated gas called
17:34plasma.
17:36The particles of plasma are so hot, they hurtle at high speed in every direction.
17:42So like the pinball, the photon can't take a direct route out.
17:47It's forever colliding with obstacles moving at thousands of miles an hour.
17:53With hundreds of thousands of miles of plasma to cross between the sun's core and its surface,
18:00even though it's traveling at the speed of light,
18:05a photon of sunlight will take between 10,000 and a million years just to get from the core of
18:13the sun to the surface.
18:20And then, freedom.
18:29What we think of as sunlight's journey, the 90 million miles from the sun to the earth,
18:35is only the last eight minutes of an odyssey that could have taken thousands and thousands of years.
18:50But this extraordinary journey raises a question.
18:59Fusion in the core never stops.
19:02So why does the sun's activity go up and down with the 11-year solar cycle?
19:16To understand, we need to know what's happening between the core and the surface.
19:25As the sun's plasma gets heated from below, it rises up to the surface of the sun, like steam rising
19:32in a kettle.
19:34The plasma is so hot, it is also electrically charged.
19:39And because it moves up and down with the convection currents, this creates huge magnetic fields.
19:49And that's not all.
19:51The sun, like the earth, spins on an axis.
19:55So plasma also flows sideways.
20:02And as the sun builds up to solar maximum, the magnetic fields get wound up and tangled.
20:13At times of high solar activity, those magnetic loops break out from the surface of the sun, drawing the sun's
20:21plasma with them.
20:23This one loop is many times bigger than the earth.
20:29But solar maximum has another implication.
20:33It's when the sun sends pulses of solar wind towards the earth.
20:38The solar wind is a constant stream of particles flowing out from the sun, bombarding the earth's own magnetic field.
20:50We can't see it directly, but we can see its effects.
21:00The aurora.
21:01The legendary northern and southern lights.
21:08This is time-lapse photography of the aurora seen from the International Space Station.
21:20But to see this evidence of the solar wind with your own eyes, you need to head not to the
21:26most sun-drenched parts of the world,
21:30but to some of the coolest, and at a time of year when they receive the least sunlight.
21:42This is Lapland in Arctic Sweden.
21:46It's February, negative 19 degrees, and a moonless winter night is about to fall.
21:56These are perfect aurora conditions.
22:08As the solar wind encounters the earth's magnetic field,
22:12it sends energy down our magnetic field lines toward the poles,
22:17causing our atmosphere to luminesce in ghostly colors.
22:22That's what creates the aurora.
22:28Now is a good time to see it, because the solar maximum is when the solar wind gusts most strongly.
22:43Patricia Cowan knows better than anyone what it takes to capture the aurora.
22:48She was so bewitched by it, she moved from England to live in Lapland.
22:54Patricia's photographed the aurora thousands of times in the 16 years she's lived here.
23:00The very first time I saw the aurora was a really nerve-tingling experience,
23:06because I had read and sort of explored a little bit about the aurora,
23:11but had no conception of the hugeness, the size, the sense of energy that the aurora gives.
23:22And when you are out alone under this totally mind-blowing experience, it just makes you feel very, very small.
23:31And even though that was 15, 16 years ago, I can still remember how I felt and what I saw
23:40that night.
23:40I don't think that will ever, ever leave me. Never.
23:50It may be cold here in Lapland, but this is a hot spot for seeing the aurora.
23:58The people who live here know that it's not the twilight days of winter,
24:02but it's dark nights when the sun makes its most spectacular appearance.
24:15Thousands of people come here from across the globe to see the northern lights.
24:27But it's not just tourists and photographers who are drawn here.
24:31It's a perfect backdrop for scientists interested in an important question.
24:37How well is our magnetic field holding up to the constant battering of the solar wind?
24:59The aurora is but a faint trace of the solar wind's true strength.
25:08Out there is a violent collision where it meets the Earth's magnetic field.
25:15That thin shell gives us vital shelter.
25:22It's the last night in Sweden for our camera crew.
25:25It's tonight or never.
25:28Oh my goodness, look at those stars.
25:31It's so clear.
25:38Oh my goodness, look at that!
25:41Look what's happening in the sky!
25:46With ordinary cameras you can see it faintly, but to capture it in its full glory, you need time-lapse
25:53cameras.
26:02It just gives me an absolute physical vibe and thrill.
26:08I cannot imagine ever living anywhere that I can't experience the northern lights during the rest of my lifetime.
26:15It means that much to me.
26:20The aurora is a stunningly beautiful display of the solar wind.
26:24But it's also a reminder that thanks to our magnetic field, the majority never reaches us.
26:33It's a mere hint of the vast amount of radiation and particles that the Sun sends our way.
26:47During periods of high solar activity, the magnetic loops in the Sun's atmosphere become tangled and knotted, and occasionally they
26:57snap.
27:00A billion tons of mass from the Sun being ejected into space.
27:05Such eruptions are called coronal mass ejections.
27:10These solar storms are the most high-energy events in the solar system,
27:14and the Sun unleashes more of them at solar maximum than at any other time.
27:21The clouds of plasma they send our way travel at alarming speeds.
27:26To cover the 90 million miles from the Sun, seen here reduced in scale on the right,
27:32to the Earth on the left, can take less than a day.
27:50Solar storms can destroy satellites, silence communications, and ground aircraft.
28:07But the link in our modern lives it threatens most is our dependence on electricity.
28:16The highly charged particles of coronal mass ejections can induce powerful electrical currents on the Earth's surface,
28:25overloading circuits and melting transformers.
28:30This could take out lighting, heating, our ability to refrigerate and cook food,
28:37operate fuel pumps, sanitation, and water supplies.
28:46We know we're vulnerable because we've been hit in the past.
28:51In Quebec, the entire power grid went down after a solar storm in 1989,
28:57plunging millions into freezing darkness.
29:04But we're not helpless.
29:06Technology and systems are already being built that are resilient to solar storms,
29:11and the best thing of all would be to have an early warning system.
29:16Fortunately, there is one inside this building.
29:23The Space Weather Prediction Center in Colorado is the only team on the planet solely dedicated to watching for solar
29:31storms.
29:35The aim is to give even a few hours warning for governments, the power grid, aviation, and space industries to
29:43get ready when a storm's on its way.
29:48The forecasters have their eyes peeled for the telltale signs that a storm could be coming.
29:54Space weather really starts with sunspots.
29:57So if we don't have big, complex sunspots, we really don't have those source regions for the big, significant activity.
30:03So essentially, before we get a big event, before we get that first clue that we should start looking for
30:07the other pieces,
30:08we're really looking at the sunspots. How big are they? How much are they changing?
30:13The black and white here is as if you could see magnetically, you know, how magnetically complex they are.
30:18So essentially, the two ends of a magnet, so to speak, the white and the black, if those get very
30:23close together,
30:24you can get very, very explosive reconnections.
30:27The next piece we start looking for on chronograph images, for example, where we've essentially blocked out the sun and
30:33watched the outer atmosphere around that.
30:35We start to watch and see, with this eruption, was there a big portion of the outer atmosphere blown into
30:40space?
30:41And if so, is it headed right at us?
30:49Every one of these amazing images is being beamed to us from the new generation of solar satellites.
30:59They are our eyes in space, to keep watch over the sun.
31:05They can see the sun with visible light.
31:11Magnetic fields.
31:16X-rays.
31:20Ultraviolet.
31:25On a typical day near solar maximum, the sun will send out three coronal mass ejections.
31:35Fortunately, today, there haven't been any.
31:41But dramatic events can happen with little warning.
32:00Dramatic solar weather can happen any day, any time.
32:04Dramatic solar weather can happen any day, any time.
32:05I've picked out, from late October 2003, really, probably the last significant, really big round of space weather activity that
32:13we had.
32:14We've blocked out the sun so we can see the atmosphere.
32:17You'll see the eruption.
32:18It looks like a halo coming straight at you.
32:21It was going at tremendous speed, so it made it here in just under a day.
32:25So we have the levels one through five, just like a hurricane or tornado, and it was pegged at that
32:29five-level storm.
32:32That solar storm took out the power grid in the Swedish city of Malmo.
32:38Tens of thousands were left without electricity.
32:42On that occasion, the Earth was only struck a glancing blow.
32:46But we can't be sure that next time we'll be so lucky.
32:51Today, if we saw this happen again, we'd be able to give our partners in the key industries, like the
32:55electric power industry, a heads up to say, hey, prepare your systems, keep them as safe as you can.
33:11Day and night, solar weather is always happening.
33:18We can't afford to ignore it.
33:22But we're only just beginning to understand it.
33:28And crucially, the sun's activity is highly dependent on which stage of its cycle it's at.
33:36But the latest research suggests that the cycles themselves could be changing.
33:42We could be living through bigger shifts in the sun's behavior than we thought.
33:47And the evidence comes from a feature of the sun that's been plain to see, even before the invention of
33:53the telescope.
34:02Early astronomers like Galileo risked damaging their eyes to look at the sun on cloudy days or at sunset and
34:11sunrise.
34:13And they spotted dark features on the surface of the sun that we now know as sunspots.
34:22Thanks to those early astronomers, sunspots are one of the few clues we have of the sun's long-term behavior.
34:33The key is what causes them.
34:40It's been known for centuries that sunspots are cooler.
34:45While most of the sun's surface is at 10,000 degrees Fahrenheit, sunspots are at around 6,000.
34:57That's the same temperature as the spark from an arc welder.
35:02Cool in comparison to the rest of the sun.
35:06But sunspots are still ferociously hot, active areas.
35:11And new research is revealing something surprising about them.
35:22As the sun approaches solar maximum and the magnetic field lines beneath its surface become tangled, the flow of plasma
35:30within is disrupted.
35:32Hot material from the interior can't rise to the surface.
35:36The result is zones of cooler plasma, sunspots.
35:43They are like windows in the sun's surface, through which we can study what's happening inside the sun itself.
36:01The McMath Solar Telescope in Arizona is the largest in the world.
36:11Seventeen years ago, a study of sunspots began here, led by a group of astronomers, including Matt Penn.
36:21Matt and his colleagues began to look at the strength of the magnetic fields within sunspots.
36:29Well, sunspots have revealed a lot about the interior of the sun.
36:33It's the surface manifestation of the magnetic field.
36:36We know the sun is filled with magnetic fields on the interior and also in the atmosphere.
36:40But sunspots are the surface detail of that.
36:43The questions about what generates the magnetic field and how it changes with time can be addressed by looking at
36:47the clues that sunspots give us on the surface.
36:51So when we started making these measurements, we weren't sure exactly what we would find.
36:55One idea was that as the sunspot number increased to a maximum and then decreased to a minimum, we might
37:01see that the magnetic field would change as well.
37:03It might increase to a maximum during the maximum of a sunspot cycle and then decrease to a minimum at
37:08the minimum.
37:09Turns out that when we looked at the data, that's not exactly what we saw.
37:18Matt has found an ingenious way of measuring the strength of the sunspot's magnetic fields.
37:38Scientists Matt Penn is using a clever new technique to measure the strength of sunspot's magnetic fields.
37:45A change in the infrared light coming from them.
37:51So what we're doing is measuring the magnetic field with the spectral line and we've done a survey of about
37:553,000 sunspots over the past 10 years, measuring the magnetic field strength in each sunspot.
38:02And what he discovered is surprising. Instead of rising and falling in line with the solar cycle as expected, the
38:11magnetic strength of sunspots has been steadily decreasing year by year.
38:19As a function of time, the magnetic field in sunspots is getting weaker and weaker.
38:23Now this is important because when we look at sunspots, we don't see any sunspots with magnetic fields below a
38:28threshold, a 1,500 gauss threshold.
38:30So as this decrease continues, if it does, into the future, we'll eventually get to the point where the magnetic
38:36fields erupting from the sun can't form dark spots.
38:39So a decreasing trend means that in the future, we may not have any sunspots at all.
38:45It's an extraordinary result.
38:51The trend suggests that over and above the familiar 11-year solar cycle, there are bigger patterns in the sun's
38:58activity.
39:01And in the long term, we may be heading for an extended quiet period, what solar scientists call a grand
39:08minimum.
39:13Intriguingly, we've been here before.
39:19Thanks to those historical records, we know that around 350 years ago, sunspots almost vanished for 70 years.
39:31So this is something new, but it suggests that we might be entering a period that we saw in history.
39:35In the mid-1600s, we entered a period called the modern minimum, where the number of sunspots in successive sunspot
39:41cycles decreased.
39:42And for a while, for four sunspot cycles, there were no sunspots on the sun.
39:46During that time, there is some evidence that the climate of the Earth actually changed.
39:49And so if we are entering another minimum period like the modern minimum, we'll be very interested to see if
39:54the climate of the Earth is going to change as well.
40:00A grand minimum would be a double-edged sword.
40:05It might mean fewer solar storms, something in our favor.
40:12But it could also mean a dramatic change in our weather.
40:20The previous grand minimum coincided with a period of brutally harsh winters in Europe and North America.
40:30The River Thames in London froze solid.
40:34It was known as the Little Ice Age.
40:39Are we heading for another?
40:44So in the long-term life of the sun, we'd love to know what's going on.
40:48It's a big unknown, a big mystery.
40:51The River Thames in London
40:51We've known all of the sun, we've known all of the sun, and we've been on the planet.
41:19years old. We don't know how it was behaving a billion years ago, and we don't know what
41:26it will do a billion years from now. We're witnessing just a tiny sliver of the lifetime
41:34of the Sun. Even several hundred years of data cannot tell us if this long-term change
41:44is part of a much bigger cycle in the Sun's behavior that we've only just begun to glimpse.
41:53But what's emerging is that even the pattern we thought we knew, the 11-year solar cycle,
41:59isn't the full story. The new research is hinting that there are greater, longer-term patterns in
42:08the Sun, and they could have profound influences on our planet and on us. In this bright age of solar
42:19research, we're getting closer than ever before to understanding the hidden mysteries inside our star,
42:26the Sun.
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