Goldilocks likes her porridge not too hot, not too cold, but just right. Planets, too, can be “just right” if they’re not too close to their star, but not too far away. The “just right” zone is called the habitable zone, or the Goldilocks zone.
A team of scientists have found an exoplanet, a planet outside of our solar system, in the Goldilocks zone of its star. This exoplanet, named Kepler-186, is roughly the same size as Earth. These two qualities make Kepler-186 one of the most Earth-like planets yet discovered!
Update: Prof. Sara Seager, who was not involved in the study, weighs in on the discovery of Kepler-186f:
Sounds like a great planet to visit, if we could figure out how to travel there!
Personally I find it simply awesome that we live in a time when finding potentially habitable planets is common, and the method to find them is standardized. Kepler has [found] a handful of such planets and this is the smallest one.
In reality we cannot know if the planet is actually habitable. We need to get a sense of the atmosphere and its greenhouse effect.
You can learn more about exoplanets in Prof. Sara Seager‘s course 12.425 Extrasolar Planets: Physics and Detection Techniques on OCW.