A century of exploring the endless final frontier

People have long speculated on the existence of worlds beyond our Earth. In the 17th century’s Paradise Lost, John Milton’s angel suggested to Adam that there was not just life on the moon, but on “other Suns, perhaps/With their attendant Moons.” Alien realms and the captivating — or terrifying — beings that might live there have become a staple of the imagination, from H.G. Wells’ Martian invaders in 1897’s The War of the Worlds to the more benevolent strangers drawing smoky rings to communicate with the linguist portrayed by Amy Adams in the 2016 film Arrival.

But it has taken science a bit longer to match our imaginations. As early as the 1850s, astronomers declared that they had discovered planets beyond our solar system, but the claims didn’t hold up.

In this issue, astronomy writer Lisa Grossman tells the story of scientists’ search for other worlds, and the decades of struggle it took to confirm their existence. It wasn’t until the 1990s that researchers confirmed that planets exist outside our solar system.

Why the long wait? There were many technological challenges to surmount, as well as a long-held supposition that other solar systems would work just like ours. And if you’re not on the lookout for something completely different, how would you find it?

Grossman is an ideal teller of this tale. She studied planetary science while an undergraduate student at Cornell University, and started her career as a science journalist covering the discoveries of the Kepler space telescope, which searched for exoplanets in our galaxy. Writing this issue’s story, which is part of our Century of Science project, also gave her the opportunity to revisit earlier explorations, including the extraordinary journeys of the Voyager space probes, which were launched in 1977 to study Jupiter and Saturn. Those boxes checked, the probes just kept on going, with Voyager 1 becoming the first craft to enter interstellar space.

Part of the great fun of reporting a story like this is being able to talk with legends in the field like Candice Hansen, who worked on Voyager and was one of the first women involved in planetary missions. “She’s seen everything,” Grossman says. “She had so many great stories; she was so generous with her time.”

Grossman also got to dial up Jim Bell, a planetary scientist who was her adviser at Cornell. She had worked in his lab calibrating images from the Spirit and Opportunity Mars rovers. Her task: to try to figure out if the dark stuff in one image was the same as the dark stuff in another.

Does she ever wish she’d become a researcher, so she could be one of those folks high-fiving when a rover touches down on Mars? “Rarely,” she says, laughing. Her professional life is still focused on discovering and exploring distant worlds, with the added perk of being able to explain the science to the rest of us. We’re glad she’s on the beat, and have devoted the entire feature section to her story, as well as a gallery of some of our favorite galaxies. Enjoy!