The planet-hunting method that finds worlds by watching them not appear

Most exoplanets aren't discovered by seeing them directly — they're found by watching a star's light dim slightly on a regular schedule, as an unseen planet passes in front of it. The planet itself is never actually photographed in this method; only its shadow's timing is.

The dimming involved is often a fraction of a percent, requiring telescopes precise enough to detect a change roughly equivalent to a fly crossing in front of a distant car's headlight. That precision is what makes the whole method possible at interstellar distances.

Thousands of confirmed planets have been found this way, purely from a rhythmic flicker in starlight, without a single direct image of most of them. We know they exist entirely from the shadow they briefly cast.

Part of the deeper dive: The Curious Person's Guide to Space, the Night Sky, and What's Actually Out There.