Space

NASA has retired its Kepler space telescope, which discovered more than 2,600 planets outside our solar system during its nine-year life span.

The news: Kepler has finally run out of fuel. NASA has decided to retire the spacecraft, letting it continue its current orbit around the sun for eternity. Engineers realized it was running very low on fuel earlier this summer and extracted the last of the data.

Voyage of discovery: Kepler was NASA’s first planet-hunting mission, and it was wildly successful: so far it has discovered 2,662 exoplanets in our galaxy. Its data, which is still being analyzed, indicates there are probably billions more, many of which could contain life. It also revealed the diversity of planets in our galaxy. The most common size of planet discovered by Kepler doesn’t exist in our solar system—a world between the sizes of Neptune and Earth. Scientists are expected to spend over a decade making new discoveries in the treasure trove of data Kepler provided.

Back in 2009: Kepler was launched with enough fuel for six years but managed to last for nine. It was packed with cutting-edge technology, including the largest digital camera for outer space observations at the time and the latest techniques for measuring stellar brightness.

A replacement: Several exoplanet-hunting missions are in the works, including the James Webb Space Telescope, now due to launch in 2021 after a series of delays. NASA’s newest planet hunter, the Transiting Exoplanet Survey Satellite, launched in April. It has already identified two potential planets.