A signal that appears to be a planet but is actually noise or an artifact.A false alarm in astronomy is a signal that initially appears to be a planet or another celestial object but is actually noise, instrumental artifact, or a different phenomenon. This is a common challenge in the search for exoplanets, where subtle dips in starlight or tiny wobbles in a star's motion must be carefully distinguished from random fluctuations or systematic errors.
The concept of false alarms has been inherent in astronomy since the first planet searches in the 1990s. The first confirmed exoplanet around a Sun-like star, 51 Pegasi b, was initially met with skepticism because similar signals had been false alarms.
Detection methods like the transit method look for periodic dimming of a star as a planet passes in front. However, starspots, instrumental noise, or even a binary companion can produce similar signals. Astronomers use statistical tests, multiple observations, and follow-up measurements to confirm that a signal is genuine. A false alarm occurs when a candidate passes initial screening but fails these rigorous checks.
False alarm rejection is critical in exoplanet surveys like Kepler and TESS, where thousands of candidates are filtered to find true planets.
The first exoplanet ever discovered around a pulsar, in 1992, was initially suspected to be a false alarm caused by the pulsar's own timing irregularities.



