Gravitational Microlensing

Detecting exoplanets by observing how a star's gravity bends and magnifies the light of a more distant background star.

Gravitational microlensing occurs when a foreground star passes between Earth and a distant background star. The foreground star's gravity acts as a lens, bending and magnifying the background star's light. If the foreground star has a planet, the planet creates an additional, shorter-lived spike in the magnification pattern. This method is uniquely sensitive to planets at large orbital distances and can detect planets around very distant stars, even in other galaxies. However, microlensing events are one-time occurrences that cannot be repeated, making follow-up observations impossible.