NASA's Planet-Hunting Kepler Space Telescope Will Run Out of Fuel in Just Months

In December, Kepler turned back to take a photograph of Earth, the bright smear across the right side of the image. NASA

When NASA's Kepler Space Telescope launched in 2009 with a mission of spotting planets orbiting distant stars, no one actually knew how successful it would be. The spacecraft quickly proved its worth—but its days are numbered. NASA said in a statement released Wednesday that it expects the famous exoplanet-hunting telescope will run out of fuel "within several months."

There's no precise way to know how much fuel the spacecraft has left, so the NASA team is looking for signs that the telescope is running out of gas. Once it does run out, there's no way to orient the spacecraft to send data back home, so the team wants to try to make sure they stop gathering new information before that end comes.

When Kepler originally launched, its mission was supposed to last just three and a half years, though the team behind the spacecraft wanted to be sure it wouldn't fall apart before six years. In 2012, NASA extended its work, and in 2013, after two parts broke, the Kepler spacecraft was reborn as "K2," still looking for exoplanets but wandering across the sky instead of keeping its focus fixed on one field of stars. K2 was originally meant to last for 10 "campaigns" of about three months each; it recently began the 17th.

Between the Kepler and K2 phases, the telescope has identified 2,649 confirmed exoplanets. That's almost three-quarters of the grand total of alien planets identified by scientists to date.

Read more: Kepler mission: Five of the most incredible discoveries from NASA's alien-hunting spacecraft

The Kepler telescope is far enough away from Earth and all the worlds scientists think may hold life that the NASA team isn't worried about how to dispose of the spacecraft safely. Instead, it will continue floating through space, dancing around the sun in Earth's neighborhood. Assuming the spacecraft doesn't die unexpectedly and NASA can control its demise, the last command they send will be simply to shut down the telescope's transmitters.

And while there may never be a mission quite like Kepler, NASA has plenty more exoplanets to find. As early as April 16, the agency is due to launch its next space telescope, called TESS, or the Transiting Exoplanet Survey Satellite, which has been in the works since 2005, years before Kepler even launched. While TESS will also look for slight dips in a star's brightness as a planet crosses in front of it, it will look at a much broader swath of the sky than Kepler did. The telescope is expected to spot as many as 1,500 new exoplanets.