A couple years ago, I was part of the team that discovered the first Earth-sized planet, Kepler-186f, rotating comfortably in its star’s “habitable zone,” where water can be liquid. Its sun, Kepler 186, is faint and far away from us—and a little colder than we’d like if we were to settle there—but it does have the potential for life. Nevertheless, Kepler 186f, please see yourself off the “best candidate habitable worlds” shelf.
By Sean Raymond | NAUTILUS
And the same goes for you, Kepler-62f, Gliese 667Cc, and Kepler-452b. Sure, you are all fascinating planets, but there’s something not quite ideal about each of you: Either your host star is so faint that we won’t be able to learn more about you for decades, or you’re quite a bit larger than Earth, and we’re not sure you are a true rocky planet—for all we know, you could be a masquerading “mini-Neptune.” So move aside! There’s a new standard in town, and its name is Proxima b. This planet has just about everything we’d want in Earth 2.0: It’s just a speck bigger, with only about 30 percent more mass than Earth (or slightly higher, depending on its orbital geometry); it’s almost certainly a genuine rocky planet; and it orbits smack in its star’s habitable zone.
The best part, though, is that Proxima, the planet’s star, is right next door, just 4.3 light-years away (130 times closer than Kepler 186f), the single closest star to our sun. Astronomers across the globe are drooling. We’ll be able to take actual pictures of it, to search for clues of life, within a decade. The European Extremely Large Telescope, a 39-meter behemoth under construction in Chile, should see its first light in 2024. The telescope will be able to directly image Proxima b and see it as a separate object—we won’t have to infer the planet’s presence indirectly (which is how the planet was discovered). This will grant astronomers the tantalizing opportunity to directly probe Proxima b’s atmosphere and surface. We will be able to search for signs of water and even signs of (surface) life.