The UniverseAnswer
Can a Planet Orbit Two Stars?
Two stars can circle each other while a planet travels around them both. Astronomers confirmed it by watching the moving stars dim.
THE QUESTION LIBRARY THE UNIVERSE
What Causes the Northern Lights?
The Sun supplies energy, Earth’s magnetic environment guides particles, and gases high overhead make the colors.
THE SHORT ANSWER
The northern lights appear when energetic particles, mainly electrons, collide with gases high in Earth’s atmosphere. Energy carried by the solar wind helps power the process through Earth’s magnetic environment. Oxygen and nitrogen release light in different colors. The southern lights form through the same broad process near the opposite pole.
- Solar-wind energy helps accelerate particles toward Earth’s upper atmosphere.
- Oxygen and nitrogen emit different colors after collisions.
- Auroral ovals can expand toward lower latitudes during strong geomagnetic storms.
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About this picture
Original AI-generated illustration for God Plays Dice; not a photograph of an observed aurora.
WHERE THE EVIDENCE STANDS
How sure are we?
- Energetic particles can cause oxygen and nitrogen in the upper atmosphere to emit auroral light.Ground, rocket and spacecraft observations support the physical mechanism.
- Every aurora requires a major solar storm.Auroras can occur during relatively quiet conditions as well.
- How do individual auroral curls and structures form?Researchers continue to study the small-scale processes behind changing structures.
WHAT WE DON’T KNOW YET
The detailed processes that shape particular auroral curls and changing structures remain active areas of research.
WHAT WOULD CHANGE THIS ANSWER
New measurements from spacecraft, rockets and ground instruments can refine explanations of how energy is transferred and how particular auroral shapes form.
On some nights, green curtains ripple across the sky. The light is made high above us, where particles meet the thin gases of Earth’s atmosphere.
THE LONG ANSWER
Free long answer 1 of 3 this month.
How does the Sun set the lights in motion?
The Sun continuously releases a stream of charged particles called the solar wind. When it reaches Earth, it interacts with the region shaped by our planet’s magnetic field, called the magnetosphere. Energy can build up there and later accelerate particles, especially electrons, toward the upper atmosphere. Those electrons collide with oxygen and nitrogen. The gases then release some of that energy as light.
That means the glowing curtain is in Earth’s atmosphere, even though energy from the Sun helps drive it. The process is more involved than sunlight simply reflecting off clouds. NASA’s aurora guide explains the Sun–Earth connection and the colors.
Why are auroras different colors?
Different atoms and molecules give off particular colors when they release energy. Oxygen commonly produces green light around 100 kilometers (about 60 miles) up and can also produce red light higher in the atmosphere. Nitrogen can contribute blue and pink or purple hues. Altitude, the energy of the incoming particles, and the way colors mix all affect the display.
A camera and a person may record the same display differently, especially in dim light. Our answer on colors in space photos looks at how images translate light into the colors we see.
Why are they usually near the poles?
Earth’s magnetic field helps guide energetic particles into regions around the magnetic poles. These regions form broad rings called auroral ovals. The northern display is the aurora borealis; its southern counterpart is the aurora australis. During a strong geomagnetic storm, the ovals can expand toward lower latitudes, so people farther from the poles may see the lights. A storm is not required for every aurora.
Are auroras unique to Earth?
No. Astronomers have observed auroras at other worlds, including Jupiter and Saturn. Their magnetic environments and atmospheres differ from ours, so the details differ too. The same broad idea remains: energetic particles interact with an atmosphere and create light. Scientists continue to investigate the finer processes that give individual curtains and swirls their shapes.
Keep asking
Are the colors in space photos real?
Space photos often show real measurements, but their colors may represent light our eyes cannot see.
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God Plays Dice answers big questions in plain words, with sources and one of six honest labels.
Words worth knowing (3)
- Solar wind
- A continuous flow of charged particles from the Sun into space.
- Magnetosphere
- The region around a planet where its magnetic field strongly influences charged particles.
- Auroral oval
- A broad ring around a magnetic pole where auroras are frequently observed.
Sources & further reading
(3) · Checked Nov 13, 2026
- Auroras ↗NASA ScienceOverview of the solar wind, atmospheric collisions, auroral colors and other worlds.
- What is an Aurora? ↗NOAA NESDISExplanation of the Sun–Earth connection and colors of auroras.
- NASA’s Guide to Finding and Photographing Auroras ↗NASA ScienceDescribes auroral colors and how displays can be seen and photographed.
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CONTINUE THE THREAD
Where this question leads.
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