Kepler, reborn as K2, continues hunt for exoplanets

After the near-failure of the Kepler space telescope, it was reborn as K2 and continues to search for Earth-like planets far from the solar system.

T. Pyle/NASA Ames/JPL-Caltech/File
This artist's concept depicts one possible appearance of the planet Kepler-452b, the first near-Earth-size world to be found in the habitable zone of star that is similar to our sun by the Kepler space telescope.

After seven years in space, the Kepler telescope is getting a second act, conducting a mission known as K2 Second Light.

Launched in March 2009, the Kepler space observatory was originally expected to last up to four years. It's mission: cataloging planets outside of our solar system, known as exoplanets, particularly those orbiting within their stars' habitable zones.

Kepler typically seeks planet candidates by watching for their stars to dim as the bodies transit in front of them. Through this process, and several secondary verification methods, Kepler has confirmed the existence of more than 1,000 exoplanets with more than 4,000 potential candidates as well.

Kepler has had its fair share of setbacks, as well. The data gathered by the spacecraft turned out to be unexpectedly noisy, forcing scientists to prolong the mission timeline. In July 2012, one of Kepler's four reaction wheels broke down. Less than a year later, another wheel malfunctioned, making it a challenge to rotate and orient the craft. Many scientists concluded that Kepler’s mission had have run its course.

But even after the National Aeronautics and Space Administration (NASA) decided not to fix the wheels, the agency was able to repurpose Kepler as K2 Second Light in 2014 with the help of Ball Aerospace engineers, using sunlight to balance the telescope.

“Many of us believed that the spacecraft would be saved, but this was perhaps more blind faith than insight,” said Tom Barclay, senior research scientist for the Kepler program. “The Ball team devised an ingenious solution allowing the Kepler space telescope to shine again.”

Now, two years after Kepler’s rebirth as K2, the exoplanet hunt continues. K2 has been responsible for the discovery of 38 additional confirmed planets outside of the solar system, including several of the most Earth-like planets found to date including Kepler-438b, Kepler-442b, and Kepler-452b.

“We are seeing an explosion of scientific interest in the K2 mission, with a new generation of researchers coming to the forefront,” wrote NASA’s Charlie Sobeck, the Kepler and K2 mission manager, in an agency release last week. “Already K2 is starting to make a significant contribution to the number of exoplanets known, and is finding them closer to home than those discovered by Kepler, and around brighter stars that provide enough light to make them candidates for probing their atmospheres. The promise of the mission is extensive.”

In addition to its ongoing exoplanet discovery operations, K2 has been responsible for several other updates to astrophysical theories. Data collected from its scope has contributed to the study of stellar and planetary formation models and given new insight into the “dynamics of our planetary system,” says Mr. Barclay.

K2’s next chance to shine will come this April when the space observatory participates in a worldwide observation experiment as a part of its ninth imaging campaign. Along with terrestrial observatories around the globe, K2 will look through Baade's Window (a view from Earth with relatively low interstellar dust) to the center of the Milky Way in an attempt to image exoplanets using gravitational microlensing; focusing on potential planets' gravitational distorting effect on light coming from sources behind them.

After that operation concludes this July, K2 has one more scheduled campaign set to end in September. But after the telescope’s surprising second wind, and with more than two years of fuel left in its tank, it is likely K2 will continue the exoplanetary hunt that began in 1995 until at least 2018.

“We have come a long way in the last 20 years, and with Kepler’s success we are riding the K2 mission into new territory,” Mr. Sobeck wrote.

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