This year was a banner year for planet-hunters. Though 2013 doesn’t hold the record for number of exoplanets detected, many of them are Earth-like, meaning they have masses, compositions, and orbits that put them in the sweet spot of habitability. Astronomers have found so many that some estimate that up to 22% of sunlike stars could harbor Earth-like planets.
Leading the charge has been the Kepler space telescope, an orbiting, purpose-built, planet-seeking machine that has been spotting potential exoplanets by the hundreds.
John Timmer, writing for Ars Technica:
With 34 months of data in total, the number of planet candidates has grown to over 3,500, a rise of roughly 30 percent. Although larger planets are easier to spot since they block more light, 600 of these candidates are now Earth-sized or smaller.
As far as the habitable zone goes, we’re up to 104 planet candidates. Nearly a quarter of these candidates are two times the Earth’s radius or smaller.
Kepler operates by observing the faint dimming that occurs when a planet passes between its star and the telescope. Astronomers have focused on sunlike stars, 42,000 of which have been in Kepler’s view.
Unfortunately, Kepler suffered the debilitating loss of two of its four reaction wheels, devices which keep the craft steady. Without them, its vision isn’t nearly clear enough to keep up its planet-hunting mission, and astronomers can’t shift its gaze to different parts of the universe.
But all is not lost. Kepler may soldier on with a new mission—searching for starquakes—and the time it spent looking for exoplanets has yielded so much data that it’ll be another another few years before scientists have sifted through the backlog. Who knows? Maybe 2014 will be an even better year for exoplanet enthusiasts.