Twenty years ago, astronomers looking out into the corners of our galaxy first spied exoplanets, celestial bodies orbiting stars other than our own. That discovery suggested a tantalizing possibility: somewhere out there, other Earth-like planets could be spinning around other Sun-like stars. And if there were another place in the universe that resembled our home, wouldn't it make sense that it could also host ecosystems thrumming with action? In the search for life beyond our solar system, the most logical place to look is an environment that resembles the one we already know.
Until last summer, these assumptions were mostly hypothetical. But in August, researchers made the thrilling announcement that a rocky planet one-third larger than our Earth rotates around the small star Proxima Centauri at a safe enough distance for water to exist on its surface in liquid form. Just four and a half light-years away, Proxima B (as it's being called) is one of our closest neighbors in this vast galaxy. Last month, astronomers revealed that a large telescope in the Atacama Desert of Chile had spotted an entire solar system of planets that might be able to host life. Now we can focus our alien-hunting energy on these beguiling exoplanets.
Although scientists are still perfecting the technology that will tell us what exactly is happening on the surface of these planets, it's pretty damn exciting that we live in a time where we might be getting close to answering a question that we've been asking ourselves for millennia: Are we alone in the universe? So I called up Sara Seager, a MacArthur "genius" grant–winning professor of planetary science and physics at MIT who has dedicated her career to finding habitable exoplanets. We talked about what the discoveries mean for the future of exploration, what it's like to think about the heavens while managing the realities of life on Earth, and why she's going to keep looking to the stars.
Rose Lichter-Marck: Why do you think it's important to look for exoplanets that could host life beyond Earth?
Sara Seager: As humans, we want to know what's out there. We want to know how we got here. How did our solar system come to be? How did our Earth form and evolve? How did life originate and evolve here? Most [of] what drives me to search for another Earth is a basic curiosity about who we are in the cosmos.
Some people believe that we're destroying our planet and that sometime in the future we'll have to find another planet to live on. Mars isn't too hospitable, so we better start looking around the very nearest stars.
RL-M: You've said that we're on this threshold of a new era, which you call "an awakening." Why do you see it that way? That sounds like a very hopeful thing to say.
SS: When you tell people that we have irrefutable evidence that there are planets around other stars, it changes the way they see the world. It forces people to go back and rethink their assumptions and the way they live. It's science fiction becoming science fact. And that changes everything.
RL-M: Have you ever seen the film called Another Earth? The fact that there's another planet out there that seems to be a mirror image of our own helps the characters believe in the possibility of a better life.
SS: I think the idea that we're not alone in an infinite universe helps give faith meaning.
RL-M: You've written that you feel pretty certain that we're going to discover life beyond Earth within the next twenty years.
SS: Actually, let me rephrase that: I believe that we will have the capabilities to find signs of life beyond Earth in the next twenty years.
There's no guarantee life is out there. And we can't guarantee that if there is, we won't miss it. And we also can't guarantee we're going to know it if we find it. But we will definitely have the capabilities to find signs of life.