Seasons of the Sun

01Without the Sun we would not be talking today and no one would be able to listen while drinking coffee or a cup of juice.

02We couldn't go to work, we couldn't go to school because the Sun is ultimately the source of all of the energy in our solar system and in us even.

03But it can also be the source of destruction if we don't pay close attention.

04Most days the Sun appears to be happily hovering over us providing warmth and light but it does have this bit of a mean streak if you will.

05The Sun is very dynamic it's constantly changing and when you zoom in on it and stare at it it almost looks like it's breathing.

06This is NASA's curious universe.

07Our universe is a wild and wonderful place.

08I'm Patti Boyd and in this podcast NASA is your tour guide.

09As Earth makes its annual journey around the Sun we experience that journey in the form of seasons.

10Earth's tilt in relation to the Sun determines what season we experience here on Earth.

11But did you know that the Sun goes through seasons too?

12The Sun doesn't have seasons like you and I experience.

13Its seasons of activity come and go every 11 years or so in what's called the solar cycle.

14If you've ever been around a toddler you've probably experienced how they have bursts of playful activity followed by complete crashes often with a meltdown in between right before they finally give up and fall asleep on the floor right next to their bed.

15But this will repeat the next day and the next day and the next is always leading up to nap time.

16And sometimes the meltdowns are mild and other times there's lots of screaming and tears.

17That's Sabrina Savage.

18She's a solar physicist at NASA's Marshall Space Flight Center and she studies what it means to live with a star.

19Just like a toddler the Sun has highs and lows.

20Sometimes the Sun is very active with random bursts of activity and at other times it's quiet.

21But over the span of a decade there is a distinctive pattern on the Sun that scientists can follow.

22The active period is known as solar maximum.

23This is when there is lots of activity happening on the Sun such as solar flares and sunspots.

24When the Sun is in its quiet phase it is said to be in solar minimum.

25During this time there's less activity and the Sun is pretty calm.

26Recently scientists announced that our Sun has entered a new solar cycle.

27Solar cycle 25.

28This means it's the 25th solar cycle we're monitoring since regular records began in 1755.

29We just recently moved over to a new solar cycle which is quite exciting.

30The last cycle was fairly mild and many experts who model these global flows and activity trends expect that the the new one to be similar and to be fairly mild.

31But that does not mean that we are in the clear at all.

32Large eruptions can happen at any time.

33To us the Sun and the stars appear calm as they twinkle in the sky.

34But the surface of the Sun is anything but tranquil.

35And that's because the Sun is made entirely of plasma.

36It isn't solid and so it doesn't all rotate together.

37The Sun actually spins faster at the equator than it does towards the poles.

38And this plasma of ionized particle soup creates very large magnetic fields that actually wrap around the whole Sun below the surface.

39As the plasma particle soup churns electric currents create magnetic fields.

40At home when you put a magnet on the fridge it's held in place by a magnetic force that comes from moving electric charges.

41As the electric charges move they create magnetic fields.

42These magnetic fields twist around the Sun like big magnetized rubber bands.

43Imagine twisting the middle of a rubber band faster than the ends.

44When you let go the middle will spin faster and drag the ends of the band with it.

45This is also what happens on the Sun.

46Things get messy really quickly.

47There's bound to be some twisting and tangling and breaking.

48And in essence the plasma that created the field also ends up tearing it apart.

49In some of the messy places where those knots begin to form magnetic fields are able to bubble up through the surface and form sunspots.

50The intense magnetic fields that manage to poke through the surface appear as dark blotches on the Sun.

51We call them sunspots.

52These are areas of high magnetic activity that can be up to 10 times bigger than Earth.

53In visible light, which is what we see with our eyes, sunspots appear darker than the area around them.

54However, it's a little bit more complicated than that up close.

55You'll see all of these writhing connected magnetic field lines and all of this plasma traveling along those fields.

56And it just looks like it's pulsing the whole time.

57And that's because of all of the convection underneath the surface that's causing that and moving all that plasma together.

58It's really quite a beautiful thing.

59And so very roughly speaking, it takes about 11 years, give or take, for the Sun to cycle from a smooth, quiet, global magnetic field.

60Where there aren't that many sunspots on the disk to one that is experiencing a lot of activity with a bunch of sunspots and a lot of eruptions at any given moment.

61So it's all due to magnetic fields.

62How many sunspots appear on the Sun plays an important role in the solar cycle.

63They show scientists when a new solar cycle is starting and when there may be more activity from our star.

64And so the Sun has some kind of seasons on it that are related to the number of sunspots that are visible on the surface.

65That's Dean Pesnell.

66He's the project scientist for the Solar Dynamics Observatory at NASA's Goddard Space Flight Center.

67So a sunspot appears to be a dark region on the surface of the Sun.

68They've been regularly observed since the early 1600s when people developed the first telescopes.

69But they have been recorded for about 3,000 years.

70The history of sunspot counting goes back centuries.

71Scientists today count sunspots almost the same way as they did 200 years ago.

72If you brought an 18th century astronomer to a modern observatory, they would still be able to count the spots.

73Today's satellites and high-powered telescopes are great for figuring out how the Sun works.

74However, when it comes to counting sunspots, we stick to the centuries-old method.

75That's because modern telescopes are just too accurate.

76The problem with the modern cameras is they see spots that are much smaller than a human would have seen 200 years ago using the telescopes that they have.

77We want to be able to keep using that long record of sunspot data, and that means consistent measuring.

78Every day, all around the world, solar observers count sunspots by physically drawing a map of the Sun.

79With a pencil and paper, they are able to trace sunspots using the Sun's light.

80They have a telescope, and they put a piece of paper into a little binder clip that they have there.

81And then they shine the Sun onto it, and they make a couple adjustments.

82And then the person basically draws, they trace over what they see projected onto that piece of paper.

83And then once that's done, they take the piece of paper and they take it away from the Sun, and put it over someplace else.

84And then they go through and they count the number of sunspots they see, and then they actually group them into families.

85And then that becomes the first official sunspot number of that day.

86Sketching out sunspots may seem like a pretty simple task.

87But it can be tricky when the Sun has lots of sunspots during solar maximum.

88And the people sketching sunspots need to work quickly.

89They need to finish this in a certain short period of time to make sure it's the same kind of sampling.

90And you can just see them sketching furiously, trying to make it from one side of the Sun to the other, to pick up all the details that they can see with the human eye.

91But we see much more detail now with our telescopes.

92So we rely on these hand-produced diagrams to do the sunspot number, even as we use the more precise and more accurate data to figure out what's actually happening to produce sunspots and where they go.

93That sunspot number is very important for charting the solar cycle.

94But the number of sunspots isn't the only important measurement.

95There are several ways to track solar cycle progress, such as the location of the sunspots themselves.

96So as the cycle progresses, the sunspots begin to appear closer and closer to the equator.

97And so if you map out where the sunspots appear over time, it looks a lot like a butterfly, with its outstretched wings outlined by where the sunspots first appear, moving from the poles to the equator.

98And we call this a butterfly diagram because we're very clever.

99However, these butterflies overlap a little bit, which makes it tricky to firmly announce a brand new cycle.

100Scientists keep track of sunspots to determine when there will be other types of solar activity.

101That's because huge solar explosions often originate from sunspots.

102We keep a close watch on the sun and its cycles because the sun's outbursts can impact our technology on Earth.

103The most famous of these solar storms happened in 1859.

104British astronomer Richard Carrington peered through his telescope and saw a bright, dazzling light blazing from a dark region on the sun.

105Shortly thereafter, there were great aurora.

106Aurora so bright that people at mid-latitudes could actually read newspapers by them.

107So that is what we call the Carrington storms.

108That's Dolores Knipp.

109She's a research professor at the University of Colorado Boulder, and her area of study is space weather.

110She studies how the sun's activity affects the solar system, which includes us here on Earth, too.

111The magnetic storms that the sun sends out can have dramatic effects on Earth.

112The Carrington event was so powerful, it lit the skies with bright aurora as far south as Puerto Rico, and sent floods of electric currents that threw telegraph networks into disarray.

113The Carrington event is the event where we had our first intersection between a great solar storm and a technology that we had become very dependent on.

114And that technology was the telegraph.

115What came with that was the absolute garbling of telegraph signals worldwide.

116And that went on for many hours.

117I believe it's important to know how this episodic and cyclical nature of the sun's extreme behavior can impact society.

118We are a very large, globally connected society that relies heavily on technology.

119And there are ways that this technology can be interrupted very quickly and very globally by the sun and its eruptions.

120These impacts are the result of powerful solar eruptions known as solar flares and coronal mass ejections.

121So, it's not just sunspots.

122It's all these other things that are related to the sunspots that go with the solar cycle that make it interesting to study.

123Solar flares are sudden outbursts of electromagnetic energy.

124These bright flashes can last from a few minutes to a few hours, kind of like fireworks on the sun.

125There are the things that the sun does to get rid of the magnetic field.

126The magnetic field has gotten so strong, it actually is converted into heat.

127And we get a big, bright flash of light called a solar flare.

128But the sun still has magnetic fields sticking above the surface that it would like to get rid of.

129And it does that by throwing the field off in what we call coronal mass ejections.

130These coronal mass ejections mean serious business.

131As the sun churns and appears to breathe, it can hurl particles into space like a great big sneeze.

132And so, when it sneezes, it can throw off mountains of material traveling at hundreds of miles per second through interplanetary space.

133And that happens to be where we live.

134That material can't pass through Earth's atmosphere to hurt us down on the ground.

135But at its very worst, it can affect our technology.

136The coronal mass ejections, as they pass by the Earth, can interact with the Earth's atmosphere and with the Earth's magnetic field to cause the aurora and to cause allergies in things like power stations.

137They can interfere with communications that use radio waves.

138We have a couple of examples later on in history where one of these coronal mass ejections actually affected something here on the Earth.

139The most famous is the one in March of 1989, which affected the eastern parts of the United States and Canada by taking out the power transmission lines.

140And so, it caused power blackouts in parts of the eastern seaboard of the United States and Canada.

141The March 1989 event was a one-two punch that actually set up our power grid, it seems, for more of a disturbance than we were anticipating.

142While the eruptions occurred on different days, the arrival of the material seems to have happened on the same day.

143And so, Earth's system, its atmosphere, its magnetosphere, its sphere of charged particles that surround Earth, really did not have time to recover between the first event and the second event.

144The 1989 event showed the world that we need to prepare for solar storms.

145These disruptive events are not a matter of if they will happen again, but when.

146And this is becoming a growing problem, if you think about it, as we've become completely dependent on technology, especially our space assets.

147And these coronal mass ejections can wreak havoc on communications satellites, GPS, and power grids.

148So, now it becomes kind of imperative for scientists who are looking at this going, okay, what could happen next?

149What ways does nature find to disrupt our new, favorite, absolutely essential technology?

150So, understanding what drives the Sun and how to anticipate these outbursts are extremely important, especially as we become increasingly reliant on satellite communication and continue to expand beyond the Earth's own protective magnetic field.

151While scientists have been able to unlock many of the Sun's mysteries, there are still questions left to answer.

152From the first solar spacecraft, Helios, to the recently launched solar orbiter, NASA has a long history of studying the Sun.

153We now have eyes constantly staring at the Sun with extraordinary resolution.

154At least one picture has been taken of the Sun every second for the last decade, and we never stop detecting the particles that it's constantly throwing at us.

155We really see every blemish.

156We hear every sneeze.

157And we are just at the very beginning of building up the baseline of these extraordinary observations that we need to cover at least one solar cycle and beyond.

158So, we really are at the precipice of understanding what makes the Sun a variable star.

159The Sun is such an ingrained part of our lives.

160We don't even think about it.

161We take it completely for granted.

162It's just there.

163But it's a star.

164So, we look in awe and wonder at the sky at night because of how it glitters.

165At least I do.

166It makes us think of how small we are and how much of the universe there is out there.

167But we really should be just as introspective of the daytime sky.

168Without the Sun, we would not be here today.

169It's so much more than a bright light in the sky.

170Our Sun supports life on Earth, but it also has an unpredictable side that makes it important to study.

171Over the years, we've learned a lot about our star.

172But there's still so much we don't know yet.

173And that's why scientists like Sabrina, Dean, and Dolores are so interested in studying the Sun.

174Next time you step outside on a sunny day, maybe you will think a little more about the power and mysteries of our neighborhood star.

175This is NASA's Curious Universe.

176This episode was written by Joy Ung, Lina Tran, and Vicki Woodburn.

177The Curious Universe team includes Maddie Arnold, Michaela Sosby, and Margo Wall.

178Our executive producer is Katie Ekinson.

179Special thanks to Karen Fox, the Heliophysics team, and Ryland Hegey.

180To keep up with the latest solar cycle science from NASA, check out nasa.gov slash solar cycle.

181If you liked this episode, please let us know by leaving us a review, tweeting about the show at NASA, and sharing us with a friend.

182Still curious about NASA?

183You can send us questions about this episode or a previous one, and we'll try to track down the answers.

184You can email a voice recording or send a written note to nasa-curiousuniverse at mail.nasa.gov.

185Go to nasa.gov slash curiousuniverse for more information.