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How exoplanets are found
Nobody has ever actually seen most of the 6,319 confirmed exoplanets: they were deduced from shadows, wobbles and gravity tricks. The table shows each technique's scoreboard; the prose explains each trick.
Each method and its harvest
| Method | Planets discovered | How it works |
|---|---|---|
| Transit | 4,662 | Measures the tiny dip in starlight when the planet crosses in front of its star |
| Radial velocity | 1,195 | Detects the star wobbling under the planet's gravity, via the Doppler effect |
| Gravitational microlensing | 281 | The system's gravity briefly magnifies the light of a background star |
| Direct imaging | 98 | Photographs the planet directly by blocking the star's overwhelming glare |
| Transit timing variations | 40 | A planet's transits running early or late betray an unseen neighbor |
| Eclipse timing variations | 17 | Shifts in the eclipse clock of a stellar pair give away a planet |
| Orbital brightness modulation | 9 | Subtle brightness changes the planet itself causes as it orbits |
| Pulsar timing | 8 | Irregularities in a pulsar's radio ticks reveal planets around it |
| Astrometry | 6 | Measures the star's minuscule displacement across the sky |
| Pulsation timing variations | 2 | Changes in a variable star's pulsation rhythm point to a companion |
| Disk kinematics | 1 | Disturbances in the gas of a protoplanetary disk expose a planet being born |
Four ways to find what cannot be seen
Transit (4,662 planets, 74% of the total): if the planet's orbit lines up with our line of sight, it crosses in front of its star and steals a tiny fraction of the light, sometimes under 0.01%. It is the undisputed champion of the count because telescopes like Kepler and TESS can watch hundreds of thousands of stars at once, waiting for those regular blinks.
Radial velocity (1,195): planet and star orbit a shared center of mass, so the star moves too, just a little. That back and forth stretches and squeezes its light (the Doppler effect), and precision spectrographs detect swings of a few meters per second, bicycle speed. That is how 51 Pegasi b showed up in 1995.
Direct imaging (98): the most intuitive and the hardest. The star shines billions of times brighter than the planet, so its light has to be blocked with coronagraphs to reveal the dot beside it. It works best for young, giant, distant planets still glowing from their own formation.
Gravitational microlensing (281): when a system passes exactly in front of a distant star, its gravity acts as a magnifying glass and amplifies the background light for a few days. If a planet is there, it adds a hiccup to the brightness. The catch: the alignment never repeats, so it is a discovery with no second chance.
Source: NASA Exoplanet Archive (Planetary Systems table, default solutions only), snapshot of 2026-07-09. Standard acknowledgment required by the archive: This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program.
Last updated: · Methodology and sources