Less than two months ago, NASA’s Kepler mission announced the confirmation of 700 new exoplanets, but its latest news of a single exosolar system may be a bit more exciting. Kepler has now found an Earth-like planet that may have liquid water on its surface, and the new discovery is located less than 500 light years away.

Since its launch in 2009, Kepler has been finding exoplanets with a deceptively simple technique. At any given time, it stares at thousands of stars, looking for a dip in the amount of light received from them. That dip can be caused by a planet passing in front of whatever star it is orbiting (from the perspective of Earth). By observing the time interval between these dips and the size of the dip, Kepler can calculate the planet’s orbit and radius. When this data is combined with other data from the star, astronomers can build a rough picture of what the planetary system looks like.

The new planet has been named Kepler 186f, and it is part of a five-planet system that is orbiting a red dwarf star (smaller and cooler than the Sun). What makes 186f so interesting is that its radius is only 1.1 times that of the Earth and it is orbiting its star in the habitable zone. This is the distance where, if the planet has water, then it is likely to remain in the liquid form. Liquid water is essential to life as we know it, and planets in this zone remain the top candidates to harbor some form of life.

Although NASA can’t be sure about the mass of 186f, it can make an educated guess based on previous data from planets this size. Given that estimate and the planet's size, their guess is that 186f might be a rocky planet.

The other planets in this planetary system are all smaller than 186f and orbit too close to the star to have any liquid water. Although the orbit of 186f is about 53 million kilometers from the star (Mercury's distance from the Sun), the star is much smaller. Therefore, this distance puts 186f far enough away to not boil off any water it may have.

That is about all that we know about 186f for now. Kepler doesn’t have the capacity to give information about the planet’s atmosphere, its surface temperature, or even its density. But Kepler is achieving what it set out to find—Earth-sized planets. Getting details is left to a future telescope. And according to a recent analysis, there might be 17 billion Earth-sized planets in the Milky Way alone. That's more than enough to keep any Kepler successors busy.

Science, 2014. DOI: 10.1126/science.1249403 (About DOIs).