The hunt for exomoons — the search for satellites around planets of other stars — resembles watching shadows in a theater where the spotlight keeps fading and flaring. The planet Kepler-167e, a gas giant near a scorching star, was discovered by William Borucki and his team. Now James Webb watched its passage across the star, hoping to catch a tiny dip in brightness from a moon.
But the telescope faced an invisible foe — its own 'breathing'. The sensitive NIRSpec instrument registered a slow drift, as if someone was smoothly turning a dimmer knob: thermal fluctuations in the camera created the illusion of changing light. Against this shaky background, the moon signal got lost, like a mosquito's shadow in the flickering beam of a spotlight. Out of 12 processing methods, seven pointed to a satellite one-tenth the planet's size. Yet midway through the transit, a double appeared — an event perfectly matching the planet crossing a dark starspot. Such a spot, like a colossal solar storm, could fool the detectors.
An answer will come in October 2027: only then will a new transit show whether it was a moon or a trick of the light.
The brightness drift is caused not by the star, but by the telescope itself: its camera warms and cools, flickering like a living heart.
The search for distant moons has long become real, yet still evokes scenes from 'Star Wars': somewhere out there, around gas giants, their own Endors could be hiding.