What If? Lab
What if the Sun had no sunspots?
The Sun has dark patches called sunspots. Some years it has lots. Some years it has very few. What if it had none at all?
Sunspots are darker, cooler patches on the Sun made by strong magnetic fields, and their numbers rise and fall about every 11 years. Imagine a Sun with none: what would happen to its light, to solar storms and to the auroras they bring? Once, for about 70 years, the real Sun came close.
Sunspots mark concentrated magnetic flux and track an approximately 11-year activity cycle that also drives flares, coronal mass ejections and geomagnetic storms. Between 1645 and 1715, in the Maunder minimum, sunspots almost vanished. This thought experiment separates what is measured about a quiet Sun from what remains debated.
The big question
The Sun looks smooth and bright. But it has dark patches called sunspots.
What if the Sun had no sunspots at all? Would anything change here on Earth?
Seen through special solar telescopes (never with your eyes!), the Sun's glowing surface is often freckled with dark patches called sunspots. Some years there are many; other years there are almost none.
So what if the Sun had no sunspots at all? This is a thought experiment. We can't switch sunspots off, but we can use what scientists have measured about busy and quiet Suns to work out what is known and what is still a question.
Sunspots are the most visible sign of the Sun's changing magnetic field, and they have been counted systematically for centuries. Their number rises and falls in a cycle of about 11 years.
This thought experiment asks what a spotless Sun would mean for its energy output, for solar storms and auroras, and for climate. Each step labels what is measured (fact) and what is reasoned or debated (idea).
Explore the idea
Make a prediction
If the Sun had no sunspots, how bright would it be?
If the Sun had no sunspots at all, how would its total brightness change?
Compared with a Sun at solar maximum, a spotless Sun's total irradiance would be…
- Much dimmer
- Almost the same, just a tiny bit dimmer
- Much brighter
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Established fact
Sunspots come and go about every 11 years.
Sunspot numbers rise and fall in a cycle of about 11 years.
Sunspots follow an approximately 11-year cycle tied to the reversal of the Sun's magnetic field.
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An idea scientists discuss
This is a pretend journey. A Sun with no spots is imagined.
A Sun with no spots at all is a thought experiment: what it would do to storms and auroras is reasoned from the real cycle, not measured.
Effects of a permanently spotless Sun are inferences from the observed cycle and the Maunder minimum, not predictions.
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Established fact
Sunspots are cooler than the rest of the Sun, so they look dark.
Sunspots are about 7,000°F, while the surface around them is about 10,000°F, so they look dark by comparison.
Sunspots are cooler (about 7,000°F), less dense regions within a photosphere of about 10,000°F, produced by intense magnetic flux.
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Established fact
The number of sunspots goes up and down, about every 11 years.
Sunspot numbers rise and fall in a cycle of about 11 years, from solar minimum to solar maximum and back.
Sunspot counts follow an approximately 11-year cycle; Cycle 25 began at the solar minimum of December 2019.
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Established fact
A busy Sun with spots is a tiny bit brighter.
Bright faculae around sunspots more than make up for the dark spots, so the Sun gives out a little more energy when it has many spots.
Faculae more than offset sunspot darkening, so total solar irradiance increases with sunspot activity.
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Established fact
The change is very, very small.
Over a whole 11-year cycle, the Sun's total energy changes by only about 0.1 percent.
Yearly-average total irradiance varies by about 0.1 percent, or 1.4 W/m², over a cycle.
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An idea scientists discuss
Without spots, the Sun would shine almost the same.
A Sun with no spots would probably shine about as it does at solar minimum: very slightly dimmer than when it is busy.
A permanently spotless Sun would likely hold near solar-minimum irradiance; whether other long-term changes would come with it is unknown.
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Established fact
Big storms on the Sun happen near sunspots.
Solar flares are sudden bursts of energy where magnetic field lines near sunspots tangle and cross. Coronal mass ejections, huge bubbles of particles, often come with them.
Flares release energy as magnetic fields near sunspots reorganize; coronal mass ejections often accompany them.
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Established fact
In May 2024, a big Sun storm made auroras glow in many places.
In May 2024, the strongest solar storm to reach Earth in two decades made auroras visible as far south as the southern United States and northern India.
The May 2024 storm reached G5, the top of the geomagnetic scale, for the first time since 2003; auroras were reported down to about 26° magnetic latitude.
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Established fact
Near the poles, auroras glow on many nights.
Between about 60 and 75 degrees latitude, auroras can be seen on more than half the nights of the year.
Under the auroral oval, about 60–75° latitude, auroras are visible on more than half of nights (NOAA SWPC).
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An idea scientists discuss
Without spots, faraway auroras might be rare.
With no sunspots, big storms would probably be rarer, so auroras far from the poles would be seen less often. Auroras near the poles would likely continue.
A spotless Sun would likely produce fewer major geomagnetic storms and fewer low-latitude auroras; polar auroras driven by the solar wind would likely persist.
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Established fact
From 1645 to 1715, people saw very few sunspots.
Between 1645 and 1715, very few sunspots were seen. Careful observers said the ones they did spot were the first in years.
Maunder (1894) noted the scarcity; Eddy (1976) showed the observers were diligent and confirmed the lull with carbon-14 in tree rings.
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Established fact
It was a very cold time in some places.
The Maunder minimum came during the coldest part of the Little Ice Age, when England's River Thames froze over in winter.
It coincided with the coldest phase of the Little Ice Age (about 1500–1850) in the Northern Hemisphere.
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An idea scientists discuss
Maybe the quiet Sun helped make it cold. Scientists are not sure.
Some scientists think the quiet Sun may have helped cause the cold, but no one knows how, and one example can't prove it.
NASA's SORCE material says the quiet Sun may have been partly responsible; Britannica notes the mechanism is unknown and a single episode does not prove the link.
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Established fact
Each group of spots counts as 10. Each spot counts as 1.
In the official sunspot number, each group counts as 10 and each spot as 1, so a day with no spots is zero, and the next possible number is 11.
Sunspot number = 10 × groups + individual umbrae, compiled by WDC-SILSO at the Royal Observatory of Belgium.
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Established fact
Cycle 25 began in 2019.
Cycle 1 began in 1755. Cycle 24 ran from December 2008 to December 2019, when Cycle 25 began.
Cycle 24: December 2008 to December 2019, peaking in April 2014; Cycle 25 began in December 2019.
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Established fact
Forecasts help keep astronauts and satellites safe.
Forecasting the cycle helps protect radio communications, satellites and astronauts: satellites can go into safe mode and spacewalks can wait.
Cycle forecasts let operators put satellites in safe mode and schedule spacewalks around active periods (NASA).
Sunspots today
Sunspots look dark because they are a little cooler than the rest of the Sun. They are still very, very hot!
Some groups of sunspots are bigger than the whole Earth.
NOAA's Space Weather Prediction Center explains that sunspots are about 7,000°F, while the surface around them is about 10,000°F. They are still blazing hot, but next to the brighter surface they look dark. The largest sunspot groups can be many times the size of Earth.
A sunspot can last a few hours or, for the biggest groups, months. The total number of spots rises and falls about every 11 years in the solar cycle: few at solar minimum, many at solar maximum.
NOAA SWPC describes sunspots as regions where intense magnetic flux pushes up through the photosphere, leaving areas around 7,000°F inside surroundings near 10,000°F. A spot's dark core is the umbra; the lighter, fibrous ring around it is the penumbra. Groups can grow to many times Earth's size and last from hours to months.
The official sunspot number, kept by the World Data Center SILSO at the Royal Observatory of Belgium, counts each group as 10 and each spot as 1. Numbered cycles began with Cycle 1 in 1755; Cycle 24 ran from December 2008 to December 2019, when Cycle 25 began.
A spotless Sun
Without sunspots, the Sun would shine almost the same. It would be just a tiny bit dimmer.
But there might be fewer big storms on the Sun.
You might expect a Sun without dark spots to be brighter. In fact the opposite happens. Bright patches called faculae appear around sunspots and outshine them, so the Sun gives out slightly more energy when it is busy. NASA measured the change over a cycle: only about 0.1 percent.
The bigger difference would be in solar storms. Flares and coronal mass ejections come from the tangled magnetic fields around sunspots, and they are what send the strongest auroras far from the poles. A spotless Sun would likely mean fewer of them. That is an idea based on the cycle we see, not a measurement of a spotless Sun.
NASA's SORCE fact sheet notes that total solar irradiance rises and falls by about 1.4 W/m², or 0.1 percent, over the cycle, peaking at maximum because faculae more than offset the darkening by spots. A permanently spotless Sun would therefore be marginally dimmer, by roughly the solar-minimum amount.
Flares arise where magnetic field lines near sunspots tangle and reorganize, and coronal mass ejections often follow. With fewer active regions, one would expect fewer large geomagnetic storms. The steady solar wind would continue, so polar auroras would not simply stop; how much rarer storms would become is an idea, not a forecast.
Why sunspots happen
The Sun is a huge ball of moving, glowing gas. The moving gas makes strong magnets.
Where the magnets are strongest, less heat reaches the top. That patch looks dark.
The Sun is made of electrically charged hot gas that is always moving, and moving charged gas creates magnetic fields. NASA explains that these fields get tangled, stretched and twisted. Where they are especially strong, they keep some of the heat inside the Sun from reaching the surface, so that patch is cooler and looks dark.
About every 11 years the Sun's whole magnetic field flips: its north and south magnetic poles swap places. Sunspots come and go with this same magnetic cycle.
The Sun's convecting, electrically charged plasma generates its magnetic field. Where the field is concentrated, NASA explains, it keeps some of the heat inside the Sun from reaching the surface, producing a cooler, darker spot. The surrounding active region heats up and appears bright as faculae and plage.
NASA describes the cycle as the Sun's magnetic field reversing about every 11 years, so a full magnetic cycle takes about 22. Predicting the strength of each cycle is still hard: some cycles have many spots, others very few.
When the spots went quiet
Long ago, for about 70 years, the Sun had hardly any sunspots.
It was a very cold time in some places. Scientists are still not sure if the quiet Sun helped make it cold.
Between 1645 and 1715, astronomers saw very few sunspots. Some who watched the Sun carefully said the spots they did see were the first in years. This quiet time is called the Maunder minimum, and it came in the coldest part of a chilly period called the Little Ice Age, when England's River Thames froze in winter.
Did the quiet Sun cause the cold? Britannica notes that no one knows how a quiet Sun would cool Earth, and one example does not prove it. Scientists still study the question.
Edward Walter Maunder pointed out the scarcity of sunspots between 1645 and 1715 in 1894. In 1976 John Allen Eddy showed that observers of the time had been careful, and confirmed the lull using carbon-14 in tree rings, which increases when solar activity is low.
The Maunder minimum coincided with the coldest part of the Little Ice Age (about 1500 to 1850). NASA's SORCE fact sheet says it may have been partly responsible; Britannica stresses that the mechanism is unknown and that a single episode does not prove a link. The connection remains an open research question.
Amazing facts
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Some sunspot groups are bigger than Earth.
The largest sunspot groups can cover huge areas of the Sun and be many times the size of Earth.
Large, complex sunspot groups can span many Earth diameters and last for months (NOAA SWPC).
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The Sun's magnet flips every 11 years or so.
About every 11 years, the Sun's magnetic field completely flips: its north and south magnetic poles switch places.
The solar magnetic field reverses about every 11 years, so a full magnetic cycle lasts about 22 years (NASA).
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A busy Sun is a tiny bit brighter.
Bright faculae around sunspots make the Sun give out about 0.1 percent more energy at solar maximum than at minimum.
Total solar irradiance varies by about 1.4 W/m² over a cycle, peaking at maximum because of faculae (NASA SORCE).
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Trees can tell us about the Sun long ago.
Carbon-14 in old tree rings helped scientists confirm that the Sun was quiet between 1645 and 1715.
Carbon-14 production rises when solar activity is low, so tree rings record past solar quiet; Eddy used them in 1976 (Britannica).
Words to know
- sunspot
- a darker, cooler patch on the Sun's surface caused by a strong magnetic field
- solar cycle
- the rise and fall of sunspots and solar activity, about every 11 years
- faculae
- bright patches on the Sun's surface that appear around sunspots
- solar flare
- a sudden burst of energy from the Sun, near sunspots
- coronal mass ejection
- a huge cloud of charged particles thrown out from the Sun
- aurora
- glowing lights in the sky caused by particles from the Sun hitting Earth's upper air
Discovery challenge
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Why do sunspots look dark?
Why do sunspots look dark?
Sunspots appear dark because…
- They are cooler than the surface around them
- They are holes in the Sun
- Clouds cover them
Show the answer
They are cooler than the surface around them
They are a bit cooler, so they glow less.
They are about 7,000°F, while the surface around them is about 10,000°F.
…strong magnetic fields keep some heat from reaching the surface, leaving them cooler than the surrounding photosphere.
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About how often do sunspots go from few to many and back?
About how long is one solar cycle?
The sunspot cycle has a typical length of about…
- 1 year
- 11 years
- 100 years
Show the answer
11 years
About 11 years.
About 11 years, from one solar minimum to the next.
…11 years; a full magnetic cycle, with two field reversals, is about 22.
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When the Sun has lots of spots, is it brighter or dimmer?
When the Sun has many sunspots, its total energy output is…
At solar maximum, total solar irradiance is…
- A tiny bit higher
- Much lower
- Exactly the same
Show the answer
A tiny bit higher
A tiny bit brighter, because of bright patches near the spots.
A tiny bit higher, about 0.1 percent, because bright faculae outshine the dark spots.
…about 0.1 percent higher, since faculae more than offset spot darkening.
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When did the Sun have hardly any spots for about 70 years?
When did the Maunder minimum happen?
The Maunder minimum spanned…
- 1645 to 1715
- 1900 to 1970
- 2008 to 2019
Show the answer
1645 to 1715
From 1645 to 1715.
From 1645 to 1715, when very few sunspots were seen.
…1645–1715, confirmed by Eddy in 1976 with historical records and carbon-14.
Experiments to try
- Watch What If? Lab What if auroras could be seen everywhere? Auroras glow when tiny particles from the Sun crash into the air high above Earth. Earth's magnetic field steers them toward the poles, so that is where auroras shine most. Imagine lights over the whole planet, find out what makes the colors, and see how people keep satellites safe in big solar storms.
- Watch What If? Lab What if a comet passed close to Earth? Comets are icy leftovers from when our solar system formed. Near the Sun, they warm up and grow a glowing cloud and long tails. Dust they leave behind gives us meteor showers. Astronomers have predicted comets' returns for centuries: Halley's Comet is due back in 2061.
- Watch What If? Lab What if Earth had no magnetic field? Deep inside Earth, swirling melted iron makes a magnetic field all around our planet. It turns compass needles, helps sea turtles find their way and shields our air from the solar wind. Imagine it gone, compare Earth with Mars, and find out why scientists are calm about Earth's changing field.
Explore next
- Watch What If? Lab What if auroras could be seen everywhere? Auroras glow when tiny particles from the Sun crash into the air high above Earth. Earth's magnetic field steers them toward the poles, so that is where auroras shine most. Imagine lights over the whole planet, find out what makes the colors, and see how people keep satellites safe in big solar storms.
- Watch What If? Lab What if a comet passed close to Earth? Comets are icy leftovers from when our solar system formed. Near the Sun, they warm up and grow a glowing cloud and long tails. Dust they leave behind gives us meteor showers. Astronomers have predicted comets' returns for centuries: Halley's Comet is due back in 2061.
- Watch What If? Lab What if Earth had no magnetic field? Deep inside Earth, swirling melted iron makes a magnetic field all around our planet. It turns compass needles, helps sea turtles find their way and shields our air from the solar wind. Imagine it gone, compare Earth with Mars, and find out why scientists are calm about Earth's changing field.
- Watch Try it What If? Lab What if Earth had no Moon? The Moon's pull stretches Earth's oceans and gives us most of our tides. Take the Moon away in our tide model and see what is left: the Sun still makes tides, but they are less than half as big as the Moon's.
- Watch Try it What If? Lab What if Earth had two moons? Our Moon goes round Earth in a neat, repeating loop. Add a second moon in our orbit model and watch what changes: the two moons tug on each other as well as on Earth, so their paths start to wobble.
- Watch Try it What If? Lab What if the Sun disappeared? The Sun cannot vanish, and it will keep shining for billions of years. But imagining it gone answers a real question: what keeps Earth going round? Switch off the Sun's pull in our model and Earth stops curving and travels on in a straight line.
- Watch Try it What If? Lab What if Earth rotated faster? One spin of Earth gives us one day and one night. Spin Earth twice as fast in our model and the days and nights each shrink to about six hours, with less time for the ground to warm up or cool down.
- Watch Try it What If? Lab What if Earth rotated slower? Slow Earth's spin to one turn a week in our model and a single afternoon lasts days. The ground has time to bake in the long sunshine and to chill in the long dark, so the gap between the hottest and coldest times grows far bigger.
For parents & teachers
What children will learn
- Sunspots are cooler, darker regions caused by strong magnetic fields on the Sun.
- Sunspot numbers rise and fall in a cycle of about 11 years, along with flares and solar storms.
- The Sun's total energy output changes very little over a cycle (about 0.1 percent).
- Scientists still debate how much the quiet Sun of 1645–1715 affected Earth's climate.
Recommended ages: 12 to 17 · About 15 minutes
Talk about it
- Why might a Sun with dark spots actually give out more energy than one without them?
- Why can't one quiet period on the Sun prove that a quiet Sun cools Earth?
- Why do satellite operators and astronauts care about forecasts of the solar cycle?
Try at home or in class
- Look up today's picture of the Sun from NASA's Solar Dynamics Observatory online and count the sunspot groups and spots. Work out the sunspot number: 10 for each group plus 1 for each spot. Never look at the Sun directly.
- Sprinkle iron filings (or use a compass) around a bar magnet to see the shape of an invisible magnetic field, like the fields that make sunspots.
Key vocabulary: sunspot, solar cycle, faculae, solar flare, coronal mass ejection, aurora
Where these facts come from
- Sunspots/Solar Cycle , NOAA Space Weather Prediction Center
- Aurora , NOAA Space Weather Prediction Center
- What Is the Solar Cycle? , NASA Space Place
- Sunspots and Solar Flares , NASA Space Place
- Solar Radiation and Climate Experiment (SORCE) Fact Sheet , NASA Earth Observatory
- How NASA Tracked the Most Intense Solar Storm in Decades , NASA Science
- Sun: Facts , NASA Science
- Maunder minimum , Encyclopaedia Britannica
Checked, not yet human-reviewed. Last updated October 26, 2026. Spotted a mistake? Tell us.