Nightglow

What you are looking at is the night side of a planet, generated live, by code. The planets of other stars are so far away that, even to our largest instruments, each one is a single point of light. Here, one of them comes close.

Everything you see is generated live, by code. A simulation of the planet’s atmosphere runs inside the work, and each frame is computed from it as you watch.

The planet

Imagine a young giant planet, many times the mass of Jupiter, still warm from its birth. Its only light is its own: it glows faintly with the heat of its birth.

Above its hot interior floats a thin layer of gas, where its weather happens. The work simulates that layer at half a million points, across a wide band of latitudes, with the physics that astronomers use for the weather of brown dwarfs and giant planets. The planet turns, and its turning bends every wind into currents and eddies.

The storms

Heat rises from deep inside, the way it rises in a pot of water before it boils, and it breaks through as storms.

A storm beats in bursts, the way thunderstorms on Earth and on Jupiter build, collapse and build again. Every burst lifts the layer above it and lets it fall back.

The waves

When the layer falls back, it swings, like the surface of a pond after a stone, and a ring of waves spreads from every burst.

These are gravity waves, waves of buoyancy in the air, and our own atmosphere is full of them. Here they meet, cross, and bend in the winds of the planet.

The glow

High above the clouds, the thin air glows very faintly, even at night. Satellites see this nightglow on Earth, and over thunderstorms they see it ripple, in rings.

Where a wave squeezes the air, the glow grows brighter. On Earth the glow lies in layers, one above another, and here there are three. A wave reaches each of them in turn, so the light climbs as it spreads.

Lightning

In the heart of a burst, lightning flashes now and then. For an instant it lights the cloud from within.

Then the cloud is dark again, and a new ring leaves the storm. Watch the centre of a fresh ring: that is where the storm has just beaten.

The grains of light

The picture is made of grains of light, about half a million of them, the way a camera made for the dark catches light a few particles at a time.

The grains are carried by the wind, and they are born where the light is, so they gather on the rings. Each one leaves its exact share of light in four pixels. Together, they are the image.

The satellite

We watch from a satellite in orbit, looking down at a slant toward the horizon. The planet curves away beneath us.

The lens keeps the middle sharp, and softens the edges and the corners, as real lenses do. As the satellite drifts, the layers of light slide past one another, and the depth appears.

The weather

The turning of the planet shapes everything. It gathers the winds into bands that blow east and west, and it spins the storms into vortices.

How fast the planet turns, and how quickly its winds fade, decide what kind of weather it has: fine and restless, or wide and swirling. These are the rules that astronomers use to understand the weather of giant planets and brown dwarfs.