NASA’s Kepler spacecraft, which discovered thousands of planets beyond the Solar System, has died at the age of 9.

The agency announced that Kepler had run out of fuel and would cease its scientific mission during a press conference on 30 October. The telescope had downloaded all the data it had collected to mission control prior to its demise.

“It was the little spacecraft that could,” says Jessie Dotson, Kepler project scientist at NASA’s Ames Research Center in Moffett Field, California. “It always did everything we asked of it, and more.”

With Kepler, “we have shown there are more planets than stars in this galaxy”, says William Borucki, a now-retired space scientist who came up with the idea for the spacecraft.

Searching for starlight

The hard-working telescope soared into space aboard a Delta II rocket in March 2009. For four years, Kepler stared at more than 150,000 stars in the constellations Cygnus and Lyra, watching for flickers of starlight. From those tiny fluctuations, Kepler scientists deduced when planets were passing across the face of the stars as seen from Earth, temporarily dimming their light.

Mechanical failures in the system that helped to orient the planet-hunter crippled Kepler’s ability to orient itself in space in 2013. NASA came up with a plan called K2 that directed the probe to look within a narrow slice of the sky aligned with the plane of the Solar System’s planets. The spacecraft’s second lease on life enabled researchers to continue discovering planets, as well as to study nearby bright stars.

Between them, the Kepler and K2 missions discovered 2,681 confirmed planets. Among those are Kepler-186f , an Earth-size planet in the habitable zone of its star, and Kepler-22b , one of many that turned out to be between the size of Earth and Neptune. Planets the size of Kepler-22b aren't found in our Solar System, but they're common throughout the Milky Way.

Nearly 2,900 more potential planets spotted by Kepler await confirmation.

NASA’s planet-hunting days aren’t over, though. The Transiting Exoplanet Survey Satellite , which launched in April, has already spotted dozens of potential distant worlds .