Astronomers have discovered the first Earth-sized planet in the "habitable zone," or the distance from a star that a water can pool on the planet's surface.
The new planet, Kepler-186f, resides about 500 light-years away from us in the constellation Cygnus (pictured below).
Wait, rewind. What is Kepler?
And what's an exoplanet?
The new planet is the outermost of five planets in the system.
Kepler-186f orbits a smaller, cooler star that's half the size and mass of our sun, meaning it might be more of an Earth cousin than an Earth twin.