Astronomy
Exoplanets
Quick fact
The first confirmed exoplanets were discovered in 1992 around a pulsar, not a Sun-like star. The first exoplanet orbiting a Sun-like star, 51 Pegasi b, was found in 1995 and is a 'hot Jupiter' that orbits its star every 4 days.
Why this is interesting
Did you know that most stars in the night sky likely host planets? Yet until 1992, we didn't know of a single one beyond our own Sun. What worlds might be hiding around our nearest neighbours?
Read the full explanation
Understanding Exoplanets
An exoplanet is simply a planet that orbits a star other than the Sun. Before the 1990s, we only had our own solar system as a model. Now, thanks to powerful telescopes and clever detection methods, we've confirmed over 5,000 exoplanets. The most successful method is the transit method: when a planet crosses in front of its star, it blocks a tiny fraction of the star's light, causing a periodic dip in brightness. Another key method is the radial velocity method, which detects the star's slight wobble due to the gravitational pull of an orbiting planet. These techniques have revealed an astonishing variety: planets larger than Jupiter that orbit scorchingly close to their star (hot Jupiters), small rocky worlds in the habitable zone (where liquid water could exist), and even planets that drift alone through space.
A deeper explanation
Exoplanets matter because they reveal that planetary systems are common and incredibly diverse. The discovery of hot Jupiters challenged our models of planet formation, which predicted large planets only far from their star. This forced scientists to rethink how planets migrate. Studying exoplanet atmospheres can tell us about their composition, temperature, and even potential biosignatures—gases like oxygen or methane that might indicate life. The ultimate importance of exoplanets lies in the search for Earth-like worlds in the habitable zone. With next-generation telescopes like the James Webb Space Telescope, we can analyze the light passing through exoplanet atmospheres, bringing us closer than ever to answering the age-old question: are we alone?