1 00:00:00,000 --> 00:00:02,050 There’s a rhythm emanating from the Sun 2 00:00:02,050 --> 00:00:04,620 to the edges of the solar system. 3 00:00:04,620 --> 00:00:09,920 Roughly every 11 years, our star ramps up to a turbulent state expelling violent eruptions. 4 00:00:09,920 --> 00:00:13,120 After a peak, it calms down to a quieter phase, 5 00:00:13,120 --> 00:00:15,320 before starting all over again. 6 00:00:15,320 --> 00:00:17,680 This is known as the solar cycle. 7 00:00:17,680 --> 00:00:22,150 This ebb and flow of solar activity affects the entire solar system 8 00:00:22,150 --> 00:00:25,370 including spacecraft electronics and astronauts 9 00:00:25,370 --> 00:00:29,670 that can be affected by particle radiation if they’re not sufficiently protected. 10 00:00:29,670 --> 00:00:34,690 Understanding the solar cycle is one of the oldest problems in solar physics 11 00:00:34,690 --> 00:00:40,540 and now, predicting it is more critical than ever as we venture to the Moon and Mars, and beyond. 12 00:00:40,540 --> 00:00:43,690 So, here are ways we’ve learned about tracking it. 13 00:00:43,690 --> 00:00:46,760 [Text: 1: Count sunspots] 14 00:00:46,760 --> 00:00:49,090 So, welcome to the dome. 15 00:00:49,090 --> 00:00:50,830 Today, we’re going to observe the Sun 16 00:00:50,830 --> 00:00:53,750 and see if it has some sunspots. 17 00:00:53,750 --> 00:00:55,640 Every morning when the skies are clear, 18 00:00:55,640 --> 00:00:59,460 Olivier looks through this telescope in search of sunspots. 19 00:00:59,460 --> 00:01:03,750 These are dark blotches on the Sun that are the main source of solar eruptions. 20 00:01:03,750 --> 00:01:06,750 They appear and disappear on the Sun’s surface. 21 00:01:06,750 --> 00:01:08,540 So, we’re not looking at the Sun. 22 00:01:08,540 --> 00:01:13,790 In fact, we’re looking at the shadow of the instrument. 23 00:01:13,790 --> 00:01:18,200 Then we put the paper always at the same place 24 00:01:18,200 --> 00:01:21,050 and then we can start drawing. 25 00:01:21,050 --> 00:01:26,500 Olivier and a team of sun observers record the pattern of sunspots by pencil. 26 00:01:26,500 --> 00:01:31,010 The first known record of sunspots date back to around a thousand years ago in China. 27 00:01:31,010 --> 00:01:36,580 After the invention of the telescope in the 17th century, routine observations were made. 28 00:01:36,580 --> 00:01:39,980 Today, sunspot drawers still use the same technique. 29 00:01:39,980 --> 00:01:44,870 While we’ve created satellites that can see the Sun in much more detail in recent decades, 30 00:01:44,870 --> 00:01:49,330 drawing by hand keeps the centuries-long record consistent. 31 00:01:49,330 --> 00:01:52,980 The sunspot number record goes back farther than any other instrument 32 00:01:52,980 --> 00:01:57,560 allowing scientists to analyze the Sun’s behavior over many, many solar cycles.  33 00:01:57,560 --> 00:02:02,760 Sunspot numbers are collected from observatories around the world and are averaged. 34 00:02:02,760 --> 00:02:07,560 During every 11-year cycle, the number of sunspots rise from zero to a peak 35 00:02:07,560 --> 00:02:09,640 and then go back down to zero again. 36 00:02:09,640 --> 00:02:16,060 Scientists use these numbers to determine when a new solar cycle begins and how active a cycle is. 37 00:02:16,060 --> 00:02:22,740 Solar maximum, the period of highest activity, can vary wildly from cycle to cycle. 38 00:02:22,740 --> 00:02:27,520 The more sunspots there are, the higher the frequency of solar storms of all types — 39 00:02:27,520 --> 00:02:32,860 some that create aurora and some that can affect power grids on Earth. 40 00:02:32,860 --> 00:02:35,560 But sunspot number isn’t the only indicator we see; 41 00:02:35,560 --> 00:02:38,600 these numbers are often combined with other signs. 42 00:02:38,600 --> 00:02:39,430 [Text: 2: Track location of sunspots] 43 00:02:39,430 --> 00:02:40,920 At the beginning of each cycle, 44 00:02:40,920 --> 00:02:45,460 sunspots appear on the Sun in the midlatitudes for a brief few hours to days. 45 00:02:45,460 --> 00:02:49,430 At solar minimum, there are often days without any spots at all. 46 00:02:49,430 --> 00:02:51,240 As the Sun becomes more active, 47 00:02:51,240 --> 00:02:56,110 sunspots form closer to the equator and can stick around for weeks to months. 48 00:02:56,110 --> 00:03:00,210 These sunspot patterns give clues to what drives the solar cycle — 49 00:03:00,210 --> 00:03:03,080 the twisting of the Sun’s magnetic field. 50 00:03:03,080 --> 00:03:07,260 Like Earth, the Sun has a magnetic field with a north and south pole. 51 00:03:07,260 --> 00:03:11,990 But unlike Earth, the Sun’s magnetic field becomes extremely complex. 52 00:03:11,990 --> 00:03:14,120 This is because the Sun is made of plasma — 53 00:03:14,120 --> 00:03:17,110 a charged gas that generates electric currents. 54 00:03:17,110 --> 00:03:22,360 As the Sun rotates, plasma around the equator moves faster than near the poles, 55 00:03:22,360 --> 00:03:26,780 causing the magnetic fields to become stretched, elongated and then twisted. 56 00:03:26,780 --> 00:03:30,610 Then Kinks in the magnetic fields burst through the surface 57 00:03:30,610 --> 00:03:33,200 as sunspots larger than the size of Earth. 58 00:03:33,200 --> 00:03:35,380 As the solar cycle unfolds, 59 00:03:35,380 --> 00:03:39,330 more sunspots appear and the magnetic field becomes more tangled. 60 00:03:39,330 --> 00:03:43,840 At the peak of the solar cycle, the Sun’s magnetic field flips — 61 00:03:43,840 --> 00:03:46,760 the north pole switches to the south and vice versa. 62 00:03:46,760 --> 00:03:49,950 The cycle then ramps down ready to start a new cycle. 63 00:03:49,950 --> 00:03:56,010 Scientists can eventually see the result of this flip within sunspots using satellites. 64 00:03:56,010 --> 00:03:58,460 [Text: 3: Spot new sunspots] 65 00:03:58,460 --> 00:04:02,590 This black and white image of the Sun shows the magnetic field on the surface. 66 00:04:02,590 --> 00:04:05,220 Most sunspots appear in pairs. 67 00:04:05,220 --> 00:04:09,150 Like a magnet, one side is positive and the other is negative. 68 00:04:09,150 --> 00:04:11,870 After they form, they gradually disappear again 69 00:04:11,870 --> 00:04:16,810 leaving behind remnants of magnetic fields that move towards the Sun’s poles. 70 00:04:16,810 --> 00:04:24,070 Eventually each pole accumulates enough magnetic fields forcing the Sun’s poles to flip at the peak of the cycle. 71 00:04:24,070 --> 00:04:29,560 Then new sunspot groups appear with the polarities in the opposite direction. 72 00:04:29,560 --> 00:04:36,000 Scientists look for a consistent string of these new sunspots in order to declare the next solar cycle. 73 00:04:36,000 --> 00:04:39,550 But the transition between cycles is slow and messy. 74 00:04:39,550 --> 00:04:46,270 Cycles often overlap creating freckles of old and new sunspots on the Sun at the same time. 75 00:04:46,270 --> 00:04:52,140 Scientists can only determine we’re in the new cycle when the number of new sunspots overtake old ones, 76 00:04:52,140 --> 00:04:56,140 which can be six months to a year after the new cycle has begun. 77 00:04:56,140 --> 00:04:58,280 While these spots give a visible tracker, 78 00:04:58,280 --> 00:05:03,610 in recent years scientists have discovered another signal that is hard to see from Earth. 79 00:05:03,610 --> 00:05:04,040 [Text: 4: Measure strength of Sun’s poles] 80 00:05:04,040 --> 00:05:07,330 The strength of the Sun’s poles during solar minimum 81 00:05:07,330 --> 00:05:10,910 can help predict how active the next cycle will be.  82 00:05:10,910 --> 00:05:17,100 After the poles have reversed at the peak, scientists keep a close eye on it for the next few years. 83 00:05:17,100 --> 00:05:22,010 If the magnetic fields accumulated at the poles become strong during this time, 84 00:05:22,010 --> 00:05:25,320 it’s likely the next solar cycle will be an active one. 85 00:05:25,320 --> 00:05:30,280 If the buildup is weak, the next solar cycle won’t be as active. 86 00:05:30,280 --> 00:05:35,370 While we use these indicators to track the Sun, predictions are still hard. 87 00:05:35,370 --> 00:05:41,610 After all, we’ve only detailed satellite observations of the last four solar cycles 88 00:05:41,610 --> 00:05:45,660 and scientists are still learning about what causes the Sun’s cycle. 89 00:05:45,660 --> 00:05:48,560 So until we piece together those missing pieces, 90 00:05:48,560 --> 00:05:54,570 the Sun, even with its 11-year clock, will continue to surprise us. 91 00:05:54,570 --> 00:06:04,416