Astronomers have been finding exoplanets out in the cosmos for 25 years, and if we’ve learned anything about all those planets, it’s that a lot of different, weird kinds exist. They are big and hot and close to their stars. They are smaller than Earth. They are gassy and Jupiter-y. They are rocky and terrestrial. They are so cold even the most extreme earthly organisms would freeze to death. They are so hot they could melt glass. They rain glass. They are by themselves. They have neighbors. They are far away. They are right next door.
And over the years, astronomers have found more and more planets that are increasingly “like” Earth — at least in terms of their size, their distance from their stars, and potentially their compositions and characters.
On Aug. 24, 2016, astronomers announced a potentially habitable, likely rocky planet orbiting the star nearest us, Proxima Centauri. Certain corners of the internet freaked out, dubbing it an “Earth-like planet” and calling for interstellar travel. Proxima b, as the world is known, is among the smallest known exoplanets, mass-wise, and it’s as close to Earth as one can get. But it’s not substantially smaller than many others, and it’s not guaranteed to be any more Earth-like, either. Proxima b fell from the public consciousness and the front page within weeks, just one more among 3,565 other known exoplanets.
Because big announcements like this happen regularly now, every year or so, it’s easy to just say “cool” and move on. Readers are used to seeing news stories about the next-closest-to-Earth-sized planet, the maybe-could-be-Earth’s-twin planet, the no-really-this-time-it’s-like-super-close-to-maybe-being-like-how-Earth-is planet. And with that escalation, exoplanets have begun to seem very normal, even possibly boring.
