WEBVTT - How Do Sunspots Work? 0:00:01.910 --> 0:00:07.890 Welcome to BrainStuff, a production of iHeartRadio. Hey, BrainStuff. Lauren 0:00:07.910 --> 0:00:13.670 Vogelbaum here. Sunspots. The ancient Chinese referred to them as 0:00:13.850 --> 0:00:18.669 stars inside the solar orb. One Renaissance astronomer argued that 0:00:18.710 --> 0:00:23.850 they were actually undiscovered planets. Today, some believe their appearance 0:00:23.910 --> 0:00:27.390 is linked to waves of UFO sightings and paranormal activity. 0:00:28.350 --> 0:00:30.070 The rest of us wonder if they're the reason for 0:00:30.140 --> 0:00:35.380 our dropped calls or spotty radio or internet service. Sunspots 0:00:35.560 --> 0:00:39.100 are the peculiar dark spots that pop up regularly on 0:00:39.140 --> 0:00:43.210 the surface of the sun. They usually appear in pairs 0:00:43.330 --> 0:00:45.970 or in groups called belts on either side of the 0:00:46.010 --> 0:00:49.690 sun's equator, between about 40 degrees and 50 degrees latitude 0:00:49.830 --> 0:00:55.220 both north and south. Sunspots vary tremendously in size, ranging 0:00:55.280 --> 0:00:59.280 from Less than 200 miles across, that's 30 kilometers, to 0:00:59.340 --> 0:01:03.240 many times larger than Earth. Small sunspots may last for 0:01:03.280 --> 0:01:06.039 less than an hour, but larger ones can last up 0:01:06.060 --> 0:01:09.160 to six months. Some are big enough to be seen 0:01:09.200 --> 0:01:12.120 by the naked eye. Keep in mind, of course, that 0:01:12.360 --> 0:01:15.750 staring directly at the unfiltered sun is an extremely bad 0:01:15.810 --> 0:01:22.090 idea because it can permanently harm your eyes. Side note here, yes, seriously. 0:01:22.740 --> 0:01:25.780 You can observe the sun and its spots safely by 0:01:25.910 --> 0:01:29.710 using solar viewing glasses or eclipse glasses. Or if you 0:01:29.750 --> 0:01:32.770 have a telescope or binoculars, you can fit them with 0:01:32.830 --> 0:01:36.950 a specialized solar filter meant for observation. Or if you 0:01:36.970 --> 0:01:39.300 don't have any of those on hand, you can always 0:01:39.459 --> 0:01:42.480 use a pinhole projector. Punch a hole in a stiff 0:01:42.520 --> 0:01:44.860 piece of paper and with the sun at your back, 0:01:45.200 --> 0:01:48.160 project an image of it onto another surface like a 0:01:48.220 --> 0:01:51.560 wall or another piece of paper. Do not mess around 0:01:51.580 --> 0:01:57.340 with the sun. it will win. Anyway, sunspots appear dark 0:01:57.460 --> 0:02:01.460 to us when viewed safely because they're cooler in temperature 0:02:01.520 --> 0:02:05.980 than the surrounding areas on the sun's visible surface. This 0:02:06.080 --> 0:02:08.580 is called the photosphere, and it has a temperature of 0:02:08.639 --> 0:02:14.350 about 10,000 degrees Fahrenheit, or around 5,500 Celsius. The dark 0:02:14.450 --> 0:02:18.070 interior of a sunspot can be about 40% cooler than 0:02:18.110 --> 0:02:22.130 the rest of the sun's surface. Sunspots are cooler because 0:02:22.190 --> 0:02:26.350 they're areas of intense magnetism, so intense that it inhibits 0:02:26.430 --> 0:02:29.230 the flow of hot material from the sun's interior to 0:02:29.290 --> 0:02:34.000 its surface. Sunspots occur because the sun isn't a hunk 0:02:34.060 --> 0:02:38.600 of rock like Earth, but a ball of continually circulating plasma, 0:02:39.020 --> 0:02:42.640 that is, hot electrically charged gases, that doesn't move in 0:02:42.720 --> 0:02:47.710 one piece. The interior and exterior of the sun rotate separately. 0:02:48.840 --> 0:02:52.200 And the exterior rotates more quickly at the equator than 0:02:52.300 --> 0:02:54.900 at the north and south poles. A point on the 0:02:54.940 --> 0:02:57.980 equator will only take 25 Earth days to go around, 0:02:58.380 --> 0:03:02.080 while a point near one of the poles could take 36. 0:03:02.200 --> 0:03:05.930 Over time, all of that messy and uneven movement twists 0:03:06.000 --> 0:03:09.510 and distorts the sun's main magnetic field in the same 0:03:09.570 --> 0:03:12.430 way that your bedsheets get wrinkled and bunched up when 0:03:12.490 --> 0:03:16.090 you toss and turn in your sleep. The bunched-up spots, 0:03:16.169 --> 0:03:19.140 the twists in the magnetic field lines, have so much 0:03:19.200 --> 0:03:22.880 magnetic power that they push on the circulating plasma beneath 0:03:22.960 --> 0:03:26.550 them and prevent its heat from rising directly to the surface. 0:03:28.030 --> 0:03:33.490 In other words, they become sunspots. The cooler sunspots appear darker, 0:03:33.790 --> 0:03:36.310 and the plasma blocked by them will flow into the 0:03:36.390 --> 0:03:40.560 areas surrounding them, making those even hotter and brighter than normal, 0:03:40.820 --> 0:03:44.700 thus making the sunspots stand out even more. I should 0:03:44.740 --> 0:03:48.540 say here that sunspots are still objectively very bright, about 0:03:48.580 --> 0:03:52.310 as bright as the full moon. The average sunspot is 0:03:52.370 --> 0:03:55.190 about as big as our planet, but the biggest on record, 0:03:55.270 --> 0:03:59.230 which appeared in 1947, was about 18 times as large 0:03:59.330 --> 0:04:02.770 as the whole surface area of the Earth. Due to 0:04:02.810 --> 0:04:05.350 the size of the sun, despite the slow speed of 0:04:05.390 --> 0:04:08.770 its surface rotation, a sunspot will appear to move across 0:04:08.810 --> 0:04:11.670 its surface about four times faster than a point on 0:04:11.750 --> 0:04:15.650 Earth would appear to move from space. In London, the 0:04:15.710 --> 0:04:19.230 Royal Observatory Greenwich has kept detailed records of the size 0:04:19.290 --> 0:04:24.730 and location of sunspots since 1874. Roughly every 11 years, 0:04:24.910 --> 0:04:28.729 the number of sunspots increases from nearly zero to more 0:04:28.770 --> 0:04:32.330 than 100, then decreases to near zero again as a 0:04:32.420 --> 0:04:36.600 new cycle starts. This pattern is called the sunspot cycle. 0:04:37.640 --> 0:04:41.460 Since the 1700s, sunspot cycles have varied in length between 0:04:41.460 --> 0:04:45.320 9 and 14 years. At the beginning of the cycle, 0:04:45.440 --> 0:04:49.970 sunspots form in the sun's mid-latitudes, but as the cycle progresses, 0:04:50.250 --> 0:04:54.169 they occur closer to the equator. We think the cycle 0:04:54.210 --> 0:04:57.690 occurs because the sun contains a sort of conveyor belt 0:04:57.790 --> 0:05:01.150 that circulates plasma between the sun's equator and its poles 0:05:01.230 --> 0:05:05.030 and then back again over a period of years. The 0:05:05.110 --> 0:05:08.440 idea is that when sunspots that formed early in a 0:05:08.460 --> 0:05:11.849 sunspot cycle begin to decay and They leave a kind 0:05:11.890 --> 0:05:16.270 of magnetic imprint on the moving plasma beneath them. The 0:05:16.310 --> 0:05:20.029 conveyor belt carries that plasma with those magnetic imprints towards 0:05:20.070 --> 0:05:24.630 the poles and then back inside the sun. The magnetic 0:05:24.690 --> 0:05:27.960 fields within the sun are then distorted and intensified even 0:05:28.040 --> 0:05:31.380 more before the conveyor belt sends the plasma to resurface 0:05:31.600 --> 0:05:36.260 nearer the equator. There, the plasma forms new, even more 0:05:36.300 --> 0:05:41.659 powerful sunspots. During any given sunspot cycle, activity usually rises 0:05:41.760 --> 0:05:46.190 quickly and then declines gradually. The point where sunspots reach 0:05:46.200 --> 0:05:49.430 their peak of intensity is called the solar maximum, and 0:05:49.470 --> 0:05:53.330 the low point the solar minimum. Solar minimums usually last 0:05:53.370 --> 0:05:56.549 for several years, but they sometimes go on for much longer. 0:05:57.510 --> 0:06:02.170 For example, there was a 60-year period between 1650 and 0:06:02.170 --> 0:06:05.450 1710 when there was little or no sunspot activity at all. 0:06:06.390 --> 0:06:09.450 This is called the Maunder Minimum, after the astronomer who 0:06:09.490 --> 0:06:13.850 discovered it. The cause remains a mystery, though some astronomers 0:06:13.890 --> 0:06:17.180 have theorized that it's normal for stars to occasionally go 0:06:17.240 --> 0:06:22.039 through such long, dormant periods. At the solar maximum, the 0:06:22.080 --> 0:06:26.760 Sun's magnetic poles actually flip. Like Earth, the Sun has 0:06:26.880 --> 0:06:30.179 north and south magnetic poles, around the solar minimum anyway. 0:06:30.680 --> 0:06:34.359 They get increasingly complex throughout the cycle until … at 0:06:34.400 --> 0:06:37.120 the height of solar activity every 11 years or so, 0:06:37.380 --> 0:06:42.039 they flip. So, sunspot activity is actually part of a 0:06:42.060 --> 0:06:45.810 22-ish year cycle, in which the sun's poles flip and 0:06:45.850 --> 0:06:50.089 then revert, called the Hale Cycle. All of this is 0:06:50.130 --> 0:06:54.130 a subject of interest, not just because sunspots are cool, literally, 0:06:54.150 --> 0:07:00.940 but also because of sunspots' potentially disruptive effects on power 0:07:00.980 --> 0:07:05.380 grids and radio-based communications here on Earth. And we're going 0:07:05.420 --> 0:07:07.300 to get into that, but first we're going to get 0:07:07.360 --> 0:07:16.650 into a quick break for a word from our sponsor. Okay, 0:07:17.150 --> 0:07:20.910 sunspots are connected with other solar events like flares and 0:07:20.990 --> 0:07:25.550 coronal mass ejections, or CMEs. A solar flare is a 0:07:25.570 --> 0:07:28.890 sudden release of energy from the sun, and CMEs actually 0:07:29.010 --> 0:07:32.820 shoot hot plasma from the sun into space. We don't 0:07:32.860 --> 0:07:35.920 know exactly what triggers them, but the bigger the group 0:07:35.960 --> 0:07:39.580 of sunspots that appears, the more intense such solar weather 0:07:39.800 --> 0:07:44.270 tends to be. Flares and CMEs can send enormous amounts 0:07:44.310 --> 0:07:50.530 of energy and charged particles hurtling into collision with Earth's atmosphere. Here, 0:07:50.690 --> 0:07:54.860 they can cause magnetic storms that create beautiful auroras, but 0:07:55.080 --> 0:07:59.300 also disrupt or alter radio and cell phone communication. and 0:07:59.340 --> 0:08:03.560 can wreak havoc with satellite electronics and Earth-bound electrical grids. 0:08:04.680 --> 0:08:08.430 For example, during the solar maximum of 1989, a power 0:08:08.470 --> 0:08:12.550 surge triggered by solar energy damaged transformers that were part 0:08:12.570 --> 0:08:17.090 of the Hydro-Quebec power system. That surge left 6 million 0:08:17.150 --> 0:08:20.510 people in Canada and the northeastern U.S. without electricity for 0:08:20.590 --> 0:08:24.800 more than nine hours. The increase in radiation that accompanies 0:08:24.840 --> 0:08:29.450 a solar flare is a theoretical health hazard to spacewalking astronauts, So, 0:08:29.670 --> 0:08:33.030 researchers monitor solar activity and can call for delays of 0:08:33.090 --> 0:08:37.030 work outside of spacecraft until the danger is passed. Some 0:08:37.050 --> 0:08:40.349 people have theorized that there's also a link between solar 0:08:40.390 --> 0:08:44.670 weather and changes in Earth's climate, perhaps instead of climate 0:08:44.720 --> 0:08:49.100 change being driven by human industry and agriculture. It is 0:08:49.220 --> 0:08:51.719 true that our climate is influenced by a lot of 0:08:51.800 --> 0:08:54.830 complex factors, but research has shown that the solar cycle's 0:08:54.870 --> 0:08:58.490 effect is marginal compared with human influence, like the emission 0:08:58.530 --> 0:09:04.340 of greenhouse gases. Oddly, sunspot activity can actually help ham 0:09:04.400 --> 0:09:09.219 radio reception, because the increased radiation causes the atmosphere to 0:09:09.460 --> 0:09:14.680 bend higher radio frequencies back toward Earth. The ways in 0:09:14.740 --> 0:09:17.400 which solar weather can affect us here on Earth deserves 0:09:17.440 --> 0:09:21.920 its own episode, or episodes, and that's all on my list, but... 0:09:22.490 --> 0:09:26.530 Long before people were worried about power grids, radio transmissions, 0:09:26.610 --> 0:09:32.320 and global warming, they were watching sunspots. Ancient Chinese and 0:09:32.400 --> 0:09:37.020 Greek astronomers recorded their observations of sunspots over 2,000 years ago. 0:09:37.040 --> 0:09:41.319 A thousand years ago, records from Korea mapped sunspots, too. 0:09:42.000 --> 0:09:44.380 And a myth out of central Mexico tells of a 0:09:44.440 --> 0:09:50.560 sun god with a pockmarked face, perhaps implying sunspot observations. However... 0:09:50.679 --> 0:09:54.150 While other peoples continued their records over the centuries, there 0:09:54.190 --> 0:09:57.459 was a bit of a gap in Europe. For a 0:09:57.480 --> 0:10:01.319 long time, just about everyone there accepted the Greek philosopher 0:10:01.500 --> 0:10:06.530 Aristotle's idea that the heavens were perfect and unchanging. This 0:10:06.630 --> 0:10:10.350 included the Catholic Church, which considered heavenly bodies to be 0:10:10.410 --> 0:10:16.059 extensions of divine perfection. So, for example, when a large 0:10:16.100 --> 0:10:20.580 sunspot appeared for eight days in 807 CE, they dismissed 0:10:20.640 --> 0:10:24.000 the phenomenon as the passage of the planet Mercury across 0:10:24.059 --> 0:10:29.630 the sun. In 1611, descriptions of sunspots started showing up 0:10:29.710 --> 0:10:33.670 in European literature again, from Galileo Galilei and three other 0:10:33.730 --> 0:10:37.630 astronomers spread across the continent, thanks to the development of 0:10:37.750 --> 0:10:42.550 telescopes in 1608. Back then, people would rely on Earth's 0:10:42.670 --> 0:10:46.670 atmospheric conditions, like a decent fog or a cloudy haze, 0:10:46.770 --> 0:10:50.339 especially around sunrise or sunset, to observe the sun directly. 0:10:50.360 --> 0:10:54.580 And astronomers used a pinhole projection technique, just like we 0:10:54.620 --> 0:10:58.179 might today, to restrict the light hitting a mirror or 0:10:58.220 --> 0:11:02.840 a telescope, and then study the projection. One of those 0:11:02.920 --> 0:11:06.380 astronomers of 1611, a Jesuit priest by the name of 0:11:06.450 --> 0:11:09.970 Christoph Scheiner, tried to come up with an explanation that 0:11:10.120 --> 0:11:14.189 didn't contradict the church's teachings. So he argued that the 0:11:14.250 --> 0:11:18.270 spots were undiscovered planets that orbited very close to the sun. 0:11:19.670 --> 0:11:22.910 Galileo correctly figured out that sunspots were part of the 0:11:22.960 --> 0:11:27.500 sun itself, perhaps clouds, he thought, by closely studying their 0:11:27.559 --> 0:11:30.760 movement as they neared the edge of the sun's visible surface. 0:11:32.200 --> 0:11:36.480 By the mid-1700s, European astronomers were recording and compiling their 0:11:36.559 --> 0:11:42.140 observations of sunspots on a daily basis. As scientists accumulated 0:11:42.260 --> 0:11:45.110 more and more data, they began to notice that sunspot 0:11:45.190 --> 0:11:51.270 activity ebbed and flowed in a pattern. In 1843, astronomer S.H. 0:11:51.429 --> 0:11:54.770 Schwab was the first to describe the 11-year sunspot cycle. 0:11:55.840 --> 0:11:58.440 Since then, researchers have used an array of tools to 0:11:58.480 --> 0:12:02.880 learn more. including giant solar telescopes that were specially cooled 0:12:03.220 --> 0:12:07.660 to observe the sun's light without being distorted by its heat. 0:12:07.760 --> 0:12:12.600 In 1908, astronomer George Ellery Hale discovered sunspots' magnetic nature 0:12:13.120 --> 0:12:15.829 and used that discovery to prove the existence of a 0:12:15.870 --> 0:12:21.130 large magnetic field in the sun's interior. That aforementioned 22-year 0:12:21.210 --> 0:12:25.820 Hale cycle is named after him. More recently, astronomers have 0:12:25.860 --> 0:12:31.579 discovered star spots, that is, sunspots on other stars. Hundreds 0:12:31.640 --> 0:12:35.429 of other stars' spots have been recorded. One giant star 0:12:35.510 --> 0:12:39.949 in the constellation Triangulum bore a spot 10,000 times larger 0:12:40.010 --> 0:12:44.110 than the biggest spots ever observed on our sun. Researchers 0:12:44.170 --> 0:12:47.010 think that some younger stars might be so covered in 0:12:47.070 --> 0:12:50.750 star spots that they affect the stars' overall temperature. which 0:12:50.929 --> 0:12:54.200 means that our prior assumptions about those stars' sizes could 0:12:54.240 --> 0:12:58.300 be wrong. As of this recording, in fall of 2026, 0:12:58.300 --> 0:13:02.580 we're in the middle of the 25th solar cycle since 0:13:02.700 --> 0:13:06.670 researchers started tracking them. It started with a solar minimum 0:13:06.809 --> 0:13:09.630 in 2019, and the peak of the cycle is already 0:13:09.690 --> 0:13:13.630 past us. It started in 2024 and was accompanied by 0:13:13.730 --> 0:13:19.290 unusually widespread auroras. Activity will continue decreasing through the anticipated 0:13:19.390 --> 0:13:22.920 end of the cycle in 2030. But that doesn't mean 0:13:23.000 --> 0:13:27.079 we won't necessarily see some spectacular sunspots in the near future. 0:13:28.040 --> 0:13:32.280 You can follow along with solar changes at sites like spaceweather.gov, 0:13:32.679 --> 0:13:35.810 which is the space weather prediction center of the National 0:13:35.910 --> 0:13:41.150 Oceanic and Atmospheric Administration. They share daily data. including images 0:13:41.230 --> 0:13:44.240 of the solar weather, warnings for when it might affect us, 0:13:44.800 --> 0:13:53.120 and forecasts for aurora here on Earth. Today's episode is 0:13:53.160 --> 0:13:56.699 based on the article How Sunspots Work on HowStuffWorks.com, written 0:13:56.720 --> 0:13:59.570 by Patrick J. Kiger. BrainStuff is a production of iHeart 0:13:59.610 --> 0:14:03.550 Podcasts in partnership with HowStuffWorks.com and is produced by Tyler Klang. 0:14:04.270 --> 0:14:07.420 For more shows from iHeart Podcasts, visit the iHeartRadio app. 0:14:07.840 --> 0:14:10.950 Apple Podcasts, or wherever you listen to your favorite shows.