An exoplanet is a planet orbiting a star other than the Sun. More than 6,400 are confirmed. How they are found, the first discoveries, the most Earth-like.
By The Orbital Record editorial teamPublished Last reviewed
An exoplanet is any planet beyond our solar system, usually orbiting another star. As of October 2026, NASA’s Exoplanet Archive lists 6,445 confirmed exoplanets. The first were found in 1992 around a pulsar and in 1995 around a Sun-like star; most are detected by the dimming or wobbling they cause in their stars.
Thirty years ago no one knew whether planets were common. Now we know there are more planets than stars in the Milky Way, and the question has shifted to what they are like and whether any could host life. That second question is the subject of our astrobiology guide.
An exoplanet, short for extrasolar planet, is a planet outside the solar system. Most orbit other stars; a few orbit stellar remnants such as pulsars and white dwarfs, and some drift alone through space as rogue planets.
The boundary with stars is set by mass. Objects above about 13 Jupiter masses can briefly fuse deuterium and are usually classed as brown dwarfs, failed stars that sit between the biggest planets and the smallest stars. In October 2026 NASA’s SPHEREx mission published spectra of dozens of them (SPHEREx and brown dwarf atmospheres).
NASA’s Exoplanet Archive counted 6,445 confirmed exoplanets on October 8, 2026. The tally passed 6,000 in September 2025, with more than 8,000 candidates still awaiting confirmation at the time. NASA’s Transiting Exoplanet Survey Satellite (TESS) alone has now confirmed more than 1,000 planets.
The count climbs in jumps. The Kepler space telescope, which watched one patch of sky from 2009 to 2018, found 2,681 confirmed planets on its own (the Kepler mission). Gaia’s fourth data release, due in December 2026, is expected to add the first large set of candidates found by astrometry.
Most exoplanets are found indirectly, through their effect on their star. Here are the main methods, with each one’s share of the 6,445 confirmed planets in NASA’s archive:
The first confirmed exoplanets were found in 1992 orbiting a dead star. Aleksander Wolszczan and Dale Frail timed the pulses of the millisecond pulsar PSR B1257+12 with the Arecibo radio telescope and found two planets a few times Earth’s mass (Wolszczan and Frail’s pulsar planets).
The first planet around a Sun-like star came three years later. In 1995 Michel Mayor and Didier Queloz used the ELODIE spectrograph in France to find 51 Pegasi b, a planet of about half Jupiter’s mass circling its star in just 4.2 days (the discovery of 51 Pegasi b). Nobody expected a giant planet that close and that hot. These “hot Jupiters” forced astronomers to accept that planets migrate after they form. Mayor and Queloz shared the 2019 Nobel Prize in Physics.
Exoplanets come in kinds the solar system never prepared us for. The most common type of planet in the galaxy may be one we do not have at all.
| Type | Size or mass | What it is like | Example |
|---|---|---|---|
| Hot Jupiter | Jupiter-sized | Gas giant orbiting in days, scorching hot | 51 Pegasi b, WASP-39b |
| Super-Earth | About 1 to 1.5 Earth radii | Likely rocky, larger than Earth | LHS 1140 b (borderline) |
| Sub-Neptune (mini-Neptune) | About 2 to 4 Earth radii | Rock or ice core under thick gas, or a water world | K2-18b |
| Lava world | Earth-sized or larger | So close to its star the surface may be molten | 55 Cancri e |
| Cold giant | Jupiter-sized | Far from its star, like our gas giants | HR 8799 planets |
| Rogue planet | Any | No host star, drifting alone | Found by microlensing |
Sub-Neptunes are the puzzle. Kepler data show a gap in planet sizes between about 1.5 and 2 Earth radii: small planets tend to be either rocky super-Earths or gassy sub-Neptunes, with few in between (the Fulton radius gap). The leading explanation is that some planets lose their thin gas envelopes and some do not.
The planets most often called Earth-like are rocky worlds orbiting in their star’s habitable zone, the range of distances where liquid water could exist on the surface. James Kasting and colleagues gave the zone its modern definition in 1993 (habitable zones around main sequence stars).
Leading candidates include Proxima b, the nearest exoplanet at about 4.2 light-years; TRAPPIST-1 e and its neighbors; TOI-700 d; LHS 1140 b; and Teegarden’s Star b. Being in the habitable zone does not mean a planet has water, an atmosphere or life. Our ranked comparison of the most Earth-like exoplanets explains each one and what JWST has found.
Most of these candidates orbit red dwarfs, small cool stars that make up most of the galaxy’s population. Their habitable zones are close in, which makes the planets easier to find but exposes them to violent stellar flares. The stars guide explains why red dwarfs live so long.
When a planet crosses its star, a sliver of starlight passes through its atmosphere, and molecules there absorb specific colors. Analyzing that filtered light is called transmission spectroscopy. In 2022 the James Webb Space Telescope used it to make the first definitive detection of carbon dioxide in an exoplanet atmosphere, on the hot Saturn-mass planet WASP-39b (JWST’s carbon dioxide detection).
Small rocky planets are much harder. JWST has found that several rocky planets around red dwarfs, including the two innermost TRAPPIST-1 planets, show no sign of thick atmospheres. The most publicized case is the sub-Neptune K2-18b, where a 2025 claim of a possible biosignature gas has not held up under independent reanalysis. We track that debate in K2-18b and the search for life.
Ground telescopes measure atmospheres too. In June 2026 a team using ESO’s Very Large Telescope measured winds on seven hot Jupiters and found the strongest evidence yet for exoplanet magnetic fields (exoplanet magnetic fields from winds).
TRAPPIST-1 is an ultracool red dwarf about 40 light-years away with seven Earth-sized planets, announced in 2017 (Gillon et al. 2017). The planets orbit in 1.5 to about 19 days in a near-resonant chain, and three or four lie in or near the habitable zone. It is the best laboratory we have for asking whether rocky planets around small stars can keep their air. Planet-by-planet JWST results are in our TRAPPIST-1 explainer.
Proxima Centauri, the Sun’s nearest stellar neighbor at about 4.2 light-years, hosts Proxima b, a planet of at least about one Earth mass orbiting every 11.2 days in the habitable zone. Proxima is a flare star, so whether its planet has kept an atmosphere is an open question. See our Proxima b explainer for its flares, its sibling planets and why it cannot yet be studied with JWST.
No moon of an exoplanet has yet been confidently confirmed, despite more than 6,000 known planets. In July 2026 a team using the CRIRES+ instrument on ESO’s Very Large Telescope reported what it calls the first plausible detection of an exosatellite: an object at least as massive as Jupiter orbiting a brown dwarf, which in turn orbits the young star CD-35 2722 (VLT finds a possible exomoon). If confirmed, it would open a new class of objects to study, though at that mass it blurs the line between a moon and a planet.
51 Pegasi, about 50 light-years away in Pegasus, is a Sun-like star and the host of the first planet found around a normal star. Its planet, 51 Pegasi b, is the prototype hot Jupiter.
The next decade will move from counting planets to characterizing them.
Planets are still being caught at every stage of life. In September 2026 astronomers confirmed Elias 2-24 b, about a million years old and still growing in its disk (the youngest exoplanet yet); Webb is studying dusty debris from planet-shattering collisions (extreme debris disks); and in October 2026 a white dwarf revealed what may be a “second-generation” planet born after its star died (HS 0209+0832).
For a visual introduction to detection methods, our video library includes Vox’s “How to find a planet you can’t see.”
As of October 8, 2026, NASA's Exoplanet Archive lists 6,445 confirmed exoplanets, with thousands more candidates awaiting confirmation. The count passed 6,000 in September 2025. About three quarters were found with the transit method, mostly by NASA's Kepler and TESS space telescopes, and the total grows by a few hundred every year.
The first confirmed exoplanets were two rocky worlds orbiting the pulsar PSR B1257+12, announced by Aleksander Wolszczan and Dale Frail in 1992. The first planet around a normal Sun-like star was 51 Pegasi b, a hot Jupiter found by Michel Mayor and Didier Queloz in 1995, which earned them the 2019 Nobel Prize.
Mostly indirectly. The transit method watches for a star dimming slightly as a planet crosses it, and the radial velocity method detects the star wobbling as the planet tugs on it. Together they account for more than 90% of discoveries. Microlensing, direct imaging, timing and astrometry find the rest.
Some might. Dozens of rocky planets orbit in their stars' habitable zones, where liquid water could exist on the surface. Whether any actually have water, a stable atmosphere or life is unknown. No exoplanet has yet shown a confirmed sign of life, and the best-known claim, for K2-18b, is disputed.
Not with the naked eye or a backyard telescope. Planets are billions of times fainter than their stars and sit very close to them on the sky. Large observatories with special optics have photographed about a hundred young, hot giant planets directly, but almost all exoplanets are known only from their effect on starlight.
Because they are small, dark and drowned in starlight. An Earth-sized planet crossing a Sun-like star dims it by less than 0.01%, and an Earth-mass planet makes the star wobble by only about 9 centimeters per second. Detecting either requires extremely stable instruments and years of observations.
An exoplanet's scientific name is its star's name followed by a lowercase letter, starting with b in order of discovery, so the first planet found around 51 Pegasi is 51 Pegasi b. The International Astronomical Union also runs public contests that give some planets popular names.
A rogue planet drifts through space without orbiting any star, probably after being thrown out of its home system or forming alone from a collapsing cloud. Rogue planets emit almost no light, so they are found mainly through microlensing, when one briefly magnifies a background star. NASA's Roman telescope is designed to count them.
Wolszczan and Frail, Nature, 355, 145-147, 1992
Found in 1992 the first confirmed planets beyond the Solar System. Wolszczan and Frail timed pulsar PSR 1257+12 and caught two worlds a few Earths in mass.
Mayor and Queloz, Nature, 378, 355-359, 1995
Found in 1995 the first planet orbiting a Sun-like star. Mayor and Queloz detected 51 Pegasi b, a hot Jupiter that circles its star every 4.23 days.
Charbonneau et al., The Astrophysical Journal Letters, 529, L45-L48, 2000
Detected the first planet crossing in front of its star in 2000. Charbonneau and colleagues measured HD 209458 b's size, the start of the transit method.
Marois et al., Science, 322, 1348-1352, 2008
Photographed in 2008 three giant planets orbiting the young star HR 8799. Marois and colleagues used Keck and Gemini to image a whole planetary system.
Borucki et al., Science, 327, 977-980, 2010
Found in 2010 Kepler's first five planets after watching 156,000 stars for six weeks. William Borucki's NASA mission went on to confirm 2,681 planets.
Anglada-Escudé et al., Nature, 536, 437-440, 2016
Found in 2016 Proxima b, a planet of at least 1.3 Earth masses orbiting the nearest star. Anglada-Escudé's team caught the star wobbling every 11.2 days.
Fulton et al., The Astronomical Journal, 154, 109, 2017
Found in 2017 a gap in the sizes of small planets between 1.5 and 2 Earth radii. Fulton's team split close-in worlds into super-Earths and sub-Neptunes.
Gillon et al., Nature, 542, 456-460, 2017
Found in 2017 seven Earth-size planets transiting TRAPPIST-1, a tiny star 40 light-years away. Gillon's team showed several could hold liquid water.
JWST Transiting Exoplanet Community Early Release Science Team, Nature, 614, 649-652, 2022
Detected in 2022 carbon dioxide in an exoplanet's air for the first time, on the gas giant WASP-39b. Webb's Early Release Science team saw it at 26 sigma.
NASA's short introduction to exoplanets, planets around other stars: why we study them and what their variety reveals about how planets form. A good first video on the topic. NASA
Explains how astronomers find exoplanets they cannot see, by measuring tiny stellar wobbles and faint dips in starlight. Clear graphics make the two main detection methods easy to follow. Vox
Astronomer David Kipping explains why Kepler did not deliver the dozens of truly Earth-like planets once predicted, and what the gap teaches us. A careful look at the limits of exoplanet surveys. Cool Worlds
A long Astrum episode on TRAPPIST-1, a nearby red dwarf with seven roughly Earth-sized planets, and why it is a prime target in the search for habitable worlds. Good for viewers who like detail. Astrum
Becky Smethurst's August 2026 news roundup on evidence for an atmosphere around a rocky planet in its star's habitable zone, plus new close-up images of the Sun and the Roman Space Telescope launch. Dr. Becky