Kepler space telescope

Despite being partially crippled by a series of malfunctions, the Kepler space telescope is still going strong. NASA’s premier planet hunter has found at least 104 worlds orbiting other stars during the first year since its resurrection.

Most of the confirmed planets are less than three times as wide as Earth, Ian Crossfield, an astrophysicist at the University of Arizona in Tucson, and colleagues report online July 18 at arXiv.org. Roughly a dozen are about the same size as Earth or smaller. Several worlds live in multiplanet systems such as K2-72, where four small, possibly rocky, planets are crammed into puny orbits — the longest only 24 days.

And a few worlds, despite orbiting stars that are much cooler than our sun, receive about as much solar energy as Earth, which marks them as potentially habitable. The researchers combined observations from Kepler and ground-based telescopes with statistical calculations to verify each planet candidate.

From 2009 to 2013, Kepler stared at one patch of sky, during which time it cataloged over 2,300 exoplanets (SN: 6/11/16, p. 12). After failures in two components needed to keep the telescope steady, researchers designed a new mission, dubbed K2. Since 2014, the telescope has been scanning a band of sky aligned with Earth’s orbit, gazing at one spot for about 80 days before moving on to the next (SN: 6/28/14, p. 7).

QUITE A CACHE Four tiny rocky worlds snuggled up to a cool star (illustrated) are a small sample from the Kepler telescope’s latest haul of exoplanets.