Our reading of data from the NASA Exoplanet Archive. Spot an error? Tell us at hello@adatastory.com.
In 1999 we knew of 30 planets around other stars. Today NASA's Exoplanet Archive lists 6,464. The first were heavy giants. The most common kind we find now is wider than Earth and narrower than Neptune, a size our own solar system doesn't have. Thirty-four years of discoveries, and what the way we look decided about what we found.
The first three, found in 1992 and 1994, circle a pulsar called PSR B1257+12. In 1995 came 51 Pegasi b, the first planet found around an ordinary star like the Sun: a giant 50 light-years away that goes round its star every 4.2 days. Michel Mayor and Didier Queloz, who found it, shared in the 2019 Nobel Prize in Physics.
By the end of 2009 the count stood at 405, and by the end of 2013 at 911. Then 872 were added in 2014 and 1,504 in 2016, most of them in two large batches from NASA's Kepler mission. Those two years alone account for 36.8% of every planet known. Since 2020 the archive has added about 332 a year, and 374 so far in 2026.
Almost every early planet was found by the wobble it gives its star, the radial velocity method. A heavy planet on a tight orbit makes the biggest wobble, so that is what the instruments of the 1990s could catch. All 27 found from 1995 to 1999 were heavier than Neptune, and 26 were at least half as heavy as Jupiter, which weighs about 318 Earths.
The typical planet found in those five years weighed 566 Earths, 1.78 times Jupiter; in the 2000s, 540. Since 2010 most new finds are a few Earth masses, though for 3,032 transit planets the archive has no measured mass and estimates it from the width. For many wobble planets the archive has only a minimum mass, because the tilt of the orbit is unknown: 59% of those found from 1995 to 1999. Their true masses can only be higher.
NASA launched Kepler in March 2009. It stared at one patch of sky in the constellation Cygnus and watched for the small dip in a star's light when a planet passes in front of it, a transit. The archive credits 2,787 planets to Kepler and 550 more to K2, the same spacecraft's second mission along the ecliptic: 3,337 together, 51.6% of every planet known.
Kepler was retired in October 2018, out of fuel, but its data keep paying out: 461 Kepler planets were added in 2019 or later. TESS, launched in April 2018 to watch the brightest nearby stars, has 1,024 (15.8%), and 285 of this year's 374. Before 2010, nearly every planet was found from the ground. In the 2010s, 75.6% were found from space.
A transit gives a planet's width: the bigger the planet, the deeper the dip. Of the 4,874 planets with a measured width, 3,338, or 68 of every 100, are wider than Earth and narrower than Neptune, which is 3.9 Earths across. Our solar system has nothing in between: its planets jump from Earth to Neptune. The busiest band is 2.38 to 2.83 Earths wide, with 667 planets.
Giants as wide as Jupiter, 11.2 Earths, number 704; planets narrower than Earth, 223. This counts what was found, not what is out there. A small planet makes a shallow dip that is easy to miss, so small planets are, if anything, undercounted here.