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How exoplanets are found
Not one of the 6,372 confirmed planets in this catalogue has been reached, and only a handful have ever been photographed. Everything else is inference — from a star that dimmed on schedule, or wobbled, or arrived a few seconds late. The archive records which inference was used in a single field, and these are the eleven values it can take.
The distribution below is not a fact about planets. It is a fact about methods: transits need an orbit almost edge-on from here, and wobbles favour heavy planets close in, so the catalogue is a portrait of what is easy to detect rather than of what is out there.
Transit method
4,709
The planet crosses in front of its star and the starlight dips.
Measures: Radius, Orbital period, Atmosphere composition (in follow-up)
How it works →
Radial velocity method
1,202
The star wobbles, and its light shifts colour as it does.
Measures: Minimum mass (M sin i), Orbital period, Orbit shape (eccentricity)
How it works →
Gravitational microlensing
292
Gravity bends light, and a planet adds a brief extra flash.
Measures: Mass ratio planet/star, Projected separation
How it works →
Direct imaging
97
Block the star's glare and photograph the planet itself.
Measures: Orbit (over years), Temperature, Atmosphere composition, Brightness
How it works →
Transit timing variations (TTV)
29
A known planet arrives early or late, because something else is pulling on it.
Measures: Mass of both planets, Orbital resonance, Presence of non-transiting planets
How it works →
Eclipse timing variations
17
Two stars eclipse each other on a clock, and a planet nudges the clock.
Measures: Minimum mass, Orbital period of the circumbinary planet
How it works →
Orbital brightness modulation
9
No dip needed — the system's total light rises and falls as the planet turns.
Measures: Orbital period, Rough size and temperature, Day/night contrast
How it works →
Pulsar timing
8
The most precise clocks in the universe, nudged by orbiting rock.
Measures: Mass, Orbital period, Eccentricity — all to extraordinary precision
How it works →
Astrometry
6
Measure the star's position precisely enough and you see it trace a loop.
Measures: True mass, Full three-dimensional orbit
How it works →
Pulsation timing variations
2
Some stars pulse like clocks; a planet makes the pulse arrive late.
Measures: Minimum mass, Orbital period
How it works →
Disk kinematics
1
The planet is never seen — only the wake it leaves in the gas.
Measures: Approximate mass, Orbital distance
How it works →
Why the counts look like that
Three quarters of all known exoplanets were found by transit, and that is almost entirely down to one instrument: Kepler stared at a single patch of sky for four years and measured the brightness of 150,000 stars at once. No other method scales that way. Radial velocity, the runner-up, needs a spectrograph pointed at one star at a time for years.
The methods lower down the list are not failures. Microlensing reaches planets thousands of light years away and needs no host star at all. Pulsar timing found the very first exoplanets, in 1992, and remains the most precise of all — it can detect something lighter than the Moon. Disk kinematics has found exactly one planet, but it is a planet still in the act of forming.
The methods also complement each other in a way that matters. A transit gives a radius; a radial-velocity measurement of the same planet gives a mass. Only with both do you get a density — and only then can you say whether a planet is rock, water or gas.
Counts are live from our own copy of NASA's Exoplanet Archive, refreshed daily. Each method links to its own page with the geometry, the formulas and a worked example.