From the first discovery to 6,000
People long suspected that other stars have planets, but spotting a small world lost in its star's glare was extremely hard. In 1992 Aleksander Wolszczan and Dale Frail confirmed the first planets around the pulsar PSR B1257+12, a kind of neutron star left behind by a supernova. In 1995 Swiss astronomers Michel Mayor and Didier Queloz found 51 Pegasi b, a Jupiter-sized planet circling a Sun-like star every 4.2 days, and shared the 2019 Nobel Prize in Physics. Such "hot Jupiters", gas giants hugging their stars, overturned assumptions about how planetary systems are arranged. The Kepler space telescope (2009–2018) found more than 2,600 planets, and TESS, launched in 2018, has continued the search. The NASA Exoplanet Archive's count of confirmed exoplanets passed 6,000 in September 2025.
How they are found
Most exoplanets cannot be seen directly, so astronomers detect their effects on their host stars.
| Method | Principle | Notes |
|---|---|---|
| Transit | The star dims slightly as a planet passes in front | Kepler and TESS; most discoveries |
| Radial velocity (Doppler) | The planet's pull makes the star wobble, shifting its light | Found 51 Pegasi b; measures mass |
| Gravitational microlensing | A foreground star magnifies a background star; a planet adds a blip | Distant, small planets; KMTNet |
| Direct imaging | The starlight is blocked and the planet photographed | Young giant planets on wide orbits |
The Korea Astronomy and Space Science Institute's KMTNet, with telescopes in Chile, South Africa and Australia, has watched the sky around the clock since 2015 and has found hundreds of planets by microlensing, making it one of the leading groups in the field.
Planets that could host life
The habitable or "Goldilocks" zone is the range of distances from a star where liquid water could exist on a planet's surface. In 2016 a planet in that zone was found around Proxima Centauri, the nearest star to the Sun at 4.2 light years, and in 2017 seven Earth-sized planets were confirmed around TRAPPIST-1, 40 light years away. The James Webb Space Telescope, launched in 2021, began analysing exoplanet atmospheres directly, clearly detecting carbon dioxide on WASP-39b in 2022. Claims of possible biosignature gases have been made, but there is still no accepted evidence of life beyond Earth. Astronomers now estimate that most stars in the galaxy have planets.
FAQ
- What is the nearest exoplanet?
- Proxima b, orbiting Proxima Centauri about 4.2 light years away. Even light takes over four years to get there, and current spacecraft would need tens of thousands of years.
- Is there evidence of life on exoplanets?
- Not yet. Telescopes such as JWST are actively studying their atmospheres, but no signal that can only be explained by life has been confirmed.
Sources reviewed: 2026-10-26
References
- Wolszczan, A., & Frail, D. A. (1992). A planetary system around the millisecond pulsar PSR1257+12. Nature, 355(6356), 145–147.
- Mayor, M., & Queloz, D. (1995). A Jupiter-mass companion to a solar-type star. Nature, 378(6555), 355–359.
- Borucki, W. J., et al. (2010). Kepler planet-detection mission: introduction and first results. Science, 327(5968), 977–980.
- Gillon, M., et al. (2017). Seven temperate terrestrial planets around the nearby ultracool dwarf star TRAPPIST-1. Nature, 542(7642), 456–460.
- NASA Exoplanet Science Institute. (2025). NASA Exoplanet Archive.