It’s been nearly a decade since the Kepler Space Telescope launched into orbit on an interstellar quest for undiscovered exoplanets. Now, NASA has announced the planet hunter has run out of fuel and is being retired in a safe orbit away from Earth.
After discovered more than 2,600 exoplanets, and collecting data from deep space suggesting our sky contains billions more hidden beyond our scope of exploration, Kepler leaves quite the legacy behind.
"As NASA's first planet-hunting mission, Kepler has wildly exceeded all our expectations and paved the way for our exploration and search for life in the Solar System and beyond," said Thomas Zurbuchen, associate administrator of NASA's Science Mission Directorate, in a statement.
"Not only did it show us how many planets could be out there, it sparked an entirely new and robust field of research that has taken the science community by storm. Its discoveries have shed a new light on our place in the universe, and illuminated the tantalizing mysteries and possibilities among the stars.”
When the space agency started conceiving the Kepler mission more than three decades ago we didn't know of a single planet outside our Solar System, according to the Kepler mission's founding principal investigator, William Borucki, now retired. Launched in 2009, the space telescope used state-of-the-art technology to measure the brightness of stars using the largest digital camera for outer space. Kepler’s primary goals were met just four years into the mission, at which point mechanical issues stopped observations. A quick-fix by the team allowed for a second round of observation by K2, with the spacecraft surveying more than half a million stars.
Thirty-five years after the initial mission idea, we now know that planets are everywhere. Recently, an analysis of Kepler’s discoveries found that as much as 50 percent of the stars visible in the night sky probably have rocky planets similar in size to Earth located at distances from their parent stars where liquid water might even pool on the surface.
"We know the spacecraft's retirement isn't the end of Kepler's discoveries," said Kepler’s project scientist Jessie Dotson. "I'm excited about the diverse discoveries that are still yet to come from our data and how future missions will build upon Kepler's results."
Kepler is passing the torch on to a newer planet hunter, the Transiting Exoplanet Survey Satellite (TESS) that launched earlier this year. TESS builds on Kepler’s observation campaign and new data as it searches for planets orbiting 200,000 of the brightest stars closest to Earth.