The telescope that's done the most work for expanding our knowledge of exoplanets is alive again — and it's already found another Earth-sized one to add to the list. NASA announced today that they awakened the Kepler telescope for its K2 (or "Second Light") mission, and detailed the ingenious solution that was used to fix what was wrong.
The problem the scientists were able to solve involved Kepler's reaction wheels, which are used to position the telescope for targeting. One of them failed in 2012, which only affected the telescope's fine-tuning, but when a second wheel failed in May of 2013 the project was halted. To solve this problem, scientists and engineers devised a way to use pressure from sunlight as a "virtual reaction wheel" to regain control — essentially returning it to its hobbled-yet-functional three-wheel state.
The idea was proposed at the beginning of the year, but there was no guarantee that it would work — or that the teams from NASA and Ball Aerospace would receive the budget to try it. At that point, the possibility of extending the mission "was not part of the conversation," Paul Hertz, NASA's astrophysics division director, said in the agency's press release.
K2's first confirmed planet, HIP 116454b, is 180 light-years from Earth. It's 2.5 times smaller the diameter of Earth, orbits a star smaller than our sun in nine days instead of 364, and is too hot for life (as we know it, at least).
Kepler has found more than 4,000 planet candidates since 2009
Since it was launched in 2009, the Kepler telescope has discovered over 4,000 planet candidates in our local slice of the Milky Way galaxy, a number that outpaced pre-mission estimates and painted a much richer picture of the abundance of multi-planet solar systems. It has even been able to classify which of these candidates could be habitable. The telescope's observations have been used to examine how far the planet candidates are from their host stars, as well as whether these planets are gaseous, rocky, or water-based — all important factors in determining to whether they could host life.
From here, Kepler will continue to add to NASA's already extensive catalog of exoplanets. Just as importantly, it will also play an integral role in selecting candidates for closer examination by the James Webb Space Telescope, which launches in 2018.