Caroline Morley

In the vast darkness of interstellar space, the rogue planet WISE 0855 flickers with a barely perceptible heat glow, like a cooling ember. Its temperature is only a few dozen degrees above freezing — if life existed there, it would see a sunless sky, in an eternal icy haze.

Three and a half parsecs from the Sun, among the dim stars of the southern sky, hides a world that astronomers have been trying to see for thirty years. Epsilon Indi Ab is a gas giant, cold as a winter night: its temperature is about 275 kelvins, just above the freezing point of water.

Astronomers aimed JWST at the rocky exoplanet LHS 3844 b — a world orbiting another star, where a year lasts just 11 hours. The planet is tidally locked: one side always faces the star, with a permanent scorch of 770°C, while the night side is plunged into icy darkness.