Exoplanets

Exoplanets are planets orbiting stars other than our Sun. The first confirmed detection came in 1992 (a pulsar planet); the first around a Sun-like star in 1995 (51 Pegasi b). NASA's Kepler space telescope (2009–2018) discovered 2,600+ exoplanets by detecting the tiny dimming of stars as planets pass in front. As of 2024, over 5,500 exoplanets are confirmed. The discovery that planetary systems are ubiquitous — virtually every star likely has planets — transformed the search for extraterrestrial life. Scientists estimate there may be 300 million potentially habitable (Earth-like, in the 'Goldilocks zone') planets in the Milky Way alone. The James Webb Space Telescope can analyze exoplanet atmospheres for biosignatures (oxygen, methane) — a potential sign of life.