You’re standing outside at dusk, maybe walking the dog or just looking up because the light caught your eye, and there it is. A weird, glowing purple circle in the sky. It isn’t a star. It definitely isn't a plane. Your first instinct might be to grab your phone, snap a grainy photo, and head straight to Reddit to ask if the aliens have finally arrived.
Actually, you aren't alone. Thousands of people have reported seeing these strange violet hued rings or blobs over the last few years. While it feels like something out of a low-budget sci-fi flick, the reality is a mix of high-end atmospheric physics, tech glitches, and sometimes, just plain old human agriculture.
Why a Purple Circle in the Sky Appears Out of Nowhere
Let’s talk about the most common culprit: LED grow lights. Honestly, this is the answer 90% of the time. Modern commercial greenhouses—especially those growing medicinal cannabis or high-yield tomatoes—use massive arrays of red and blue LED lights. Why? Because plants don't actually need the full spectrum of white light to grow; they crave the red and blue ends of the spectrum for photosynthesis. When those two colors mix and reflect off a low-hanging cloud layer, you get a vibrant, almost neon purple glow that looks like a portal is opening over the horizon.
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It’s a localized phenomenon. If you’re in a place like Delta, British Columbia, or parts of Arizona and Ohio, you’ve probably seen the sky turn a deep plum color at 2:00 AM. It’s light pollution, basically. But on a cloudy or misty night, that light doesn't just dissipate. It hits the water droplets in the air and spreads out into a circular or elliptical shape.
But what if there isn't a greenhouse for fifty miles?
Then things get a bit more "science-heavy." There’s a specific atmospheric event called STEVE (Strong Thermal Emission Velocity Enhancement). For a long time, people thought it was just a weird type of aurora borealis. It wasn't. NASA and citizen scientists eventually figured out that STEVE is a ribbon of hot, glowing gas. While it often looks like a picket fence of green lights, it frequently appears as a mauve or purple streak or arc. Under certain viewing angles, or when the "ribbon" is coming toward you, it can look suspiciously like a distorted purple circle in the sky.
The Physics of Atmospheric Optics
Light is a fickle thing. Sometimes, what you see is just a "glitch" in how light interacts with ice crystals. We’ve all seen halos around the moon—those are caused by hexagonal ice crystals in cirrus clouds refracting light at a $22^{\circ}$ angle. Usually, these are white or slightly rainbow-colored.
However, under very specific conditions—specifically during a "volcanic sunset"—the colors shift. After a major eruption, like Tonga in 2022, the stratosphere gets pumped full of aerosols. These tiny particles scatter blue light differently. When the sun is well below the horizon, the remaining red light mixes with scattered blue light from the upper atmosphere. The result? A vivid, localized purple patch that can appear circular as the sun's rays hit a specific pocket of moisture or dust.
It’s beautiful. It’s also a bit haunting.
Digital Artifacts and Lens Flares
We have to address the "iPhone factor." You see a purple circle in the sky through your screen, but when you look away, it disappears. That’s a lens flare. Specifically, it’s a reflection of a bright light source (like the sun or a streetlamp) bouncing off the internal elements of your camera lens.
Modern smartphone lenses have coatings to prevent this, but they aren't perfect. A bright sun just out of frame can create a magenta or purple "ghost" image. If you’re seeing the circle only on your phone, you’re looking at a reflection of the sun’s light inside your camera’s glass.
- Check if the circle moves when you tilt your phone.
- If it moves in the opposite direction of your hand, it’s a flare.
- Look at the sky with your bare eyes (safely!). If it’s gone, you’ve been "flared."
The Solar Storm Connection
We are currently hovering near a "solar maximum." This means the sun is incredibly active, throwing out Coronal Mass Ejections (CMEs) like they're going out of style. When these particles hit Earth's magnetic field, they excite nitrogen and oxygen.
Most people know that oxygen glows green. But nitrogen? At very high altitudes, ionized nitrogen produces blues and purples. During intense geomagnetic storms, these colors can become visible much further south than the typical "Northern Lights" zones. If you see a purple circle in the sky during a predicted solar storm, you’re likely witnessing the literal "bruising" of our atmosphere as it fends off solar radiation.
It's not just a pretty light show. It's high-energy physics happening in real-time. The purple specifically comes from nitrogen ions being struck by solar particles at altitudes above 200 miles. At that height, the air is so thin that the glow can linger, appearing as a hazy, circular cloud of violet light.
Fact-Checking the "Mystery"
People love a good conspiracy. You'll hear talk about "Project Blue Beam" or secret government testing. While it’s true that agencies like NASA occasionally release vapor tracers (like trimethylaluminum) to study high-altitude winds, these are usually documented. These tracers can glow red, green, or purple, but they usually disperse into long, wispy trails rather than staying in a perfect circle.
If you see a purple circle in the sky and want to know what it is, look at the weather. Is it foggy? Is there a low ceiling of clouds? Check Google Maps for "industrial greenhouses" nearby. Chances are, you'll find a massive glass building just a few miles away that’s bathing its crops in "blurple" light.
What to Do When You See One
If you're looking at a purple circle in the sky right now, don't panic. It's almost certainly a terrestrial or atmospheric event. To get the best data, try to determine its position. Use a compass app. Note the time.
- Check for Local Greenhouses: Use satellite imagery to see if there are large commercial farms within 10–20 miles.
- Verify Space Weather: Sites like SpaceWeather.com will tell you if a geomagnetic storm is hitting Earth.
- Look for STEVE: If the purple is a long arc rather than a tight circle, you’re looking at a sub-auroral ion drift.
- Check NOTAMs: If you’re near a military base, check "Notices to Air Missions." Sometimes they run tests that involve atmospheric illumination.
The phenomenon of the purple circle in the sky is a reminder that our atmosphere is a fluid, reacting constantly to both human activity and cosmic forces. Whether it’s the glow of a million LEDs or the byproduct of a solar flare hitting nitrogen atoms, it’s a sign of a world that is much more interconnected than we think.
To get the most accurate identification, use an app like SkyView to rule out planets or stars that might be distorted by atmospheric refraction. If the light is static and localized near the horizon, it's almost certainly light pollution from agriculture. If it's shimmering and high overhead, keep your eyes peeled—you're likely witnessing a rare geomagnetic event that few people ever get to see in person. Record the coordinates and the direction you're facing, as this data is genuinely helpful for atmospheric researchers tracking light pollution and auroral anomalies.