Science Section : The planet Kepler-186f image - Horseman(War)

The planet Kepler-186f, seen here in an artist's rendering, is the size of Earth. It sits in its star's habitable zone and could have liquid water on its surface-but it's not quite Earth's twin.

By: Nadia Drake

Over the past five years, we've come to realize that in our galaxy planets are everywhere. And with scientists discovering new exoplanets by the hundreds, one more world would hardly seem to add much to the cosmic menagerie of un-Earthly delights.
Yet one planet could change everything—Earth's twin.
The search for exoplanets is narrowing to one main focus: finding a planet like Earth. In that search, astronomers have been surprised to find that the more they learn, the more they find that our own solar system is pretty strange. And until recently they hadn't found a hint of a planet like Earth anywhere they looked.

See interactive: Hundreds of Exoplanets,
a Handful Right for Life
But it's just a matter of time before a true Earth analogue appears on the cosmic horizon. Now astronomers are getting ready for the next phase of exploration—searching for extraterrestrial life by looking for the collective gasps and sighs of alien life-forms—for the gases they breathe into exoplanet atmospheres.
Ultimately, the search for planets is the search for life. And we're tiptoeing closer to finding out if it's really out there.