NASA’s Kepler mission is back in the spotlight with Kepler-452b, a near-Earth-size planet discovered in the “habitable zone” around a star much like our sun.

Today, the Kepler mission is still going strong – but its mission was looking bleak several years ago. In July 2012, one of Kepler’s four reaction wheels failed. Reaction wheels on spacecraft are vital for attitude control without using fuel.

The failure of one reaction wheel wasn’t catastrophic. Kepler could still perform its planet hunting mission with three wheels. But, a second wheel failed in May 2013, and Kepler’s mission status was looking dire.

Six months after the second reaction wheel failed, an ingenious plan was presented to save Kepler’s planet hunting mission. The plan was dubbed K2 ‘Second Light.’ Scientists came up with a way to use the sun as a ‘third wheel.’

Photons from the sun exert pressure on the spacecraft. By positioning the spacecraft just right, this solar pressure balances the Kepler spacecraft. Scientists had to position the spacecraft to nearly parallel to its orbital path around the sun.

kepler second light infographic

Because scientists were using the sun as a third wheel, Kepler would no longer study just one part of the sky. K2 allows Kepler to study a particular part of the sky for up to 83 days. After that, the spacecraft needs to rotate to prevent sunlight from entering the telescope.

The original Kepler mission studied one piece of the sky.

kepler field of view

K2 widens the search to several parts of the sky.

K2 field of view

And K2 is already delivering. In December 2014, NASA announced the first exoplanet discovery under the K2 mission. HIP 116454b, is about 2.5 times the diameter of Earth. Don’t expect life on this exoplanet, though. At least, none like we’ve ever seen. It orbits its host star every nine days. HIP 116454b sits 180 light-years from Earth toward the constellation Pisces.

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Since the launch of the K2 mission, 22 exoplanets have been confirmed.

Scientists are still pouring over data from the first phase of the Kepler mission. The number of confirmed exoplanets from Kepler now stands at 1,030. Potential planet candidates sit at 4,696. Follow-up observations and additional analysis will be needed to push these candidates into the confirmed category.

K2 won’t be limited to just planet hunting. The Kepler team also plans to observe star clusters, active galaxies and supernovae.

Image credits: NASA

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