You’ve probably seen them in high-res NASA photos or maybe even through a pair of cardboard eclipse glasses. They look like holes. Little inklings of ink spilled across a glowing orange marble. We call them sunspots, but if you're looking for a more poetic or literal description, they are essentially a shadow on the sun.
Except they aren't shadows. Not in the way your house casts a shadow on the driveway.
If you could somehow scoop a sunspot out of the solar atmosphere and place it in the night sky, it would glow brighter than the full moon. It’s a trick of the light—a massive, magnetic illusion. They only look black because the rest of the sun is so blindingly, violently bright. We're talking about a temperature difference that messes with your internal sense of scale. While the "normal" surface of the sun (the photosphere) sits at a comfortable $5,500^\circ\text{C}$, these "shadows" are closer to $3,500^\circ\text{C}$. Still hot enough to vaporize any metal known to man, but cool enough to look like a void by comparison.
The magnetism behind the darkness
Why does the sun get "bruised" like this? It’s not clouds. It’s not smoke.
It’s magnets. Really, really big ones.
The sun isn't a solid rock; it’s a roiling, twisting ball of plasma. Because plasma is electrically charged, its movement creates magnetic fields. Sometimes, these magnetic field lines get all tangled up like a bunch of rubber bands that have been twisted too many times. When a particularly knotty bundle of these lines pokes through the surface, it creates a sort of "magnetic dam."
This dam is strong. It literally pushes back against the hot, rising gases from the sun's interior. In a normal spot on the sun, hot plasma rises, cools, and sinks back down—a process called convection. But in a sunspot, the magnetism is so intense it chokes off that flow. The heat can’t get through. The area stays "cool."
Imagine a boiling pot of thick oatmeal. If you hold a cold spoon just under the surface in one spot, the bubbles stop there. That’s your shadow on the sun.
It's more than just a visual glitch
These dark patches are the primary indicators of the Solar Cycle. Every 11 years, the sun goes from "quiet" to "screaming." During the Solar Maximum, the sun is peppered with these dark spots. We are currently heading toward a peak in Solar Cycle 25, and things are getting weird.
In early 2024, we saw some of the largest sunspot groups in years. One group, AR3664, became so massive it was visible to the naked eye (with proper filters, obviously). It was wider than several Earths placed side-by-side.
When people see a shadow on the sun of that magnitude, they should be thinking about their electronics. Those tangled magnetic lines eventually snap. When they do, they release more energy than a billion hydrogen bombs. This is what we call a Solar Flare or a Coronal Mass Ejection (CME).
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- Radio Blackouts: High-frequency communication gets fried.
- Power Grid Failures: The 1989 Quebec blackout was caused by solar activity.
- Satellite Damage: Spacecraft can literally get "dragged" down by an expanding atmosphere.
- The Aurora: The only beautiful part of this magnetic violence.
The anatomy of a spot
If you look closely at a photo from the Daniel K. Inouye Solar Telescope in Hawaii, you’ll see the "shadow" has layers.
The darkest part in the middle is the umbra. This is where the magnetic field is strongest and most vertical. Surrounding it is a lighter, streaky region called the penumbra. It looks like the iris of an eye. In the penumbra, the magnetic field is more tilted, allowing a little bit more heat to leak through.
It’s a violent, shifting landscape. Sunspots don't just sit there. They migrate. They grow. They merge. They rotate. A spot can last for a few days or persist for months before the magnetic field finally decays and the surrounding heat rushes back in to "heal" the dark patch.
Historical freak-outs and the Maunder Minimum
Humans have been obsessing over the shadow on the sun for centuries. Galileo famously argued about them with Jesuit scholars. Before telescopes, observers in ancient China recorded seeing "birds" or "flecks" within the sun.
But the weirdest period was between 1645 and 1715. It’s known as the Maunder Minimum. For about 70 years, sunspots almost completely vanished. The sun was "spotless."
Interestingly, this coincided with the "Little Ice Age" in Europe and North America. Thames River froze over. Crops failed. While scientists still debate exactly how much sunspot activity affects Earth's climate (it's a tiny percentage of total solar irradiance), the correlation remains one of the most studied mysteries in solar physics.
Why you should care in 2026
We are living through a period of high solar activity. If you see a news report about a "giant shadow on the sun," it’s a warning.
Modern society is incredibly fragile when it comes to space weather. We rely on GPS for everything from Uber rides to landing planes. We rely on long-distance power lines that act like giant antennas for solar induced currents. Understanding these dark spots isn't just for astronomers; it's about protecting the infrastructure of the 21st century.
National agencies like NOAA and the Space Weather Prediction Center (SWPC) monitor these spots 24/7. They look for "delta" configurations—spots where opposite magnetic polarities are packed tightly together. Those are the dangerous ones. Those are the ones that produce the X-class flares that can knock out a transformer in New Jersey from 93 million miles away.
How to see them yourself safely
Don't ever look at the sun with your bare eyes. You will burn your retinas. Seriously.
- Eclipse Glasses: Use ISO-certified glasses leftover from the last eclipse. If a sunspot is big enough, you’ll see it as a tiny black pinprick.
- Solar Projection: Use a colander or a pinhole projector to cast an image of the sun onto a white piece of paper.
- Dedicated Solar Telescopes: These use H-alpha filters to show the sun in a specific wavelength, making the "shadows" and the surrounding flares look like a 3D topographic map.
Actionable steps for the solar-conscious
Watching the sun is a hobby that pays off in awareness.
- Check the Solar Index: Visit SpaceWeather.com or the SWPC website. Look for the "Sunspot Number." If it's over 150, the sun is very active.
- Download an Aurora Alert App: If a large sunspot group is facing Earth and releases a flare, you might get a chance to see the Northern Lights much further south than usual.
- Backup Your Data: It sounds paranoid, but during extreme solar cycles, localized hardware glitches are more common. Keep a physical backup of your most important files.
- Learn the Lingo: When you hear "X-Class Flare," that’s the big one. "M-Class" is medium. "C-Class" is basically a solar sneeze.
The sun is a dynamic, living star. Those shadows are just the visible heartbeat of its magnetic engine. Keep looking up, but keep your filters on.