Astronomy
Planetary Auroras Beyond Earth
Quick fact
Jupiter's auroras are the most powerful in the solar system, emitting hundreds of times more energy than Earth's, and they are large enough to engulf our entire planet.
Why this is interesting
You've probably seen photos of Earth's northern lights, but did you know that Jupiter's moon Io can create auroras on Jupiter itself? What other worlds light up with glowing skies?
Read the full explanation
Understanding Planetary Auroras Beyond Earth
Auroras happen when charged particles—mostly electrons and protons—stream along a planet's magnetic field lines and collide with gases in the upper atmosphere. The energy from these collisions excites the gas molecules, causing them to emit light, like a neon sign. On Earth, we see them near the poles because our magnetic field funnels the particles there. On other planets, the process is the same but with different ingredients: different gases produce different colors, and the shape and location of auroras depend on the planet's magnetic field and the source of the particles.
A deeper explanation
The auroral process begins with a stream of charged particles, often from the solar wind or from a moon like Jupiter's Io, which are then captured and accelerated by a planet's magnetic field. As they spiral along the magnetic lines toward the poles, they strike the atmosphere, transferring energy to atoms and molecules. When these particles return to their ground state, they emit photons of characteristic wavelengths. For instance, oxygen produces green and red, while nitrogen yields blue and purple. On Jupiter and Saturn, auroras are not only driven by the solar wind but also by internal processes—their rapid rotation and interactions with volcanic moons—causing constant, intense auroral ovals. Understanding these off-Earth auroras helps us probe the magnetic fields and atmospheric compositions of distant worlds, and even detect magnetic fields on exoplanets.