The universe may be vast, but the conditions under which life as we know it could exist are actually very specific. It can’t be too close to a star or too far away. There has to be at least the potential for water and the ratio of gasses much be just right. A good deal of our gazing out into the cosmos focuses on tracking down planets that fit the complex matrix of conditions. Today, NASA announced that its Kepler mission has confirmed the existence of the very first planet in a “habitable zone”.
This new planet – Kepler-22b – is 2.4 times the radius of Earth, making it the “smallest yet found to orbit in the middle of the habitable zone of a star similar to our sun”. We don’t know much of anything about the terrain or gaseous make-up of Kepler-22b, but finding a planet similar to Earth’s size in the sweet spot of a habitable zone is itself cause for celebration. Kepler-22b also follows an Earth-like, 290-day orbit around its star, which is smaller and cooler but in the same class as our own sun (G-type).
Kepler identifies potential planets by tracking variations in the brightness of stars that are caused by other celestial bodies passing in front them. Once an identical blip is detected at least three times, researchers qualify the body as a potential planet. In February 2011, NASA announced 54 habitable zone planet candidates and Kepler-22b is the first of those to be confirmed as a planet. NASA also says that the increased numbers of smaller planet candidates proves that Kepler is fulfilling its mission of identifying planet candidates that are both Earth-like in size and potentially habitable, which puts us closer to finding “Earth’s twin”.