The most-prolific planet hunter to date took flight 10 years ago today.

By the time it was retired, late last year, Kepler had discovered about 5500 confirmed or possible planets. And astronomers will sift through its decade of observations for decades more.

The space telescope discovered planets by looking for a star to grow a tiny bit fainter as a planet passed in front of it, blocking some of its light. How much the star faded, and for how long, revealed the planet’s size. And repeated sightings revealed the planet’s orbit. Follow-up observations with other telescopes added more details.

Kepler’s work told us that planets come in an amazing variety — different sizes, compositions, and more. And astronomers may find even more variety as they analyze the rest of Kepler’s information.

During its original mission, Kepler kept a steady eye on about 150,000 stars. A few years into the mission, though, its pointing system failed. So NASA gave it a new mission: It looked at patches of sky for about three months at a time. It kept hunting for planets, but it also watched for exploding stars, objects in our own solar system, and more.

Kepler consumed the last of its fuel last year, so it could no longer keep a steady aim. It was shut down at the end of the year — retiring as the all-time champion planet hunter.

More about Kepler tomorrow.

Script by Damond Benningfield