For an astrophysicist who hunts for planets in other solar systems, there’s nothing more exciting than discovering one being born.
It turns out that witnessing the birth of a planet—something that has never been done before—doesn’t deliver a cinematic moment of astrophysicists huddled in an observatory and erupting in excitement at their discovery.
It unfolds more like this: one month after defending her dissertation and just before she began a postdoctoral position at Stanford, Kate Brutlag Follette ’04 ’04 decamps for the southern Atacama Desert of Chile, and the Las Campanas Observatory’s Magellan telescopes—a pair of 6.5 meter–diameter mounted telescopes on the summit of Cerro Manqui. Because of their size (anywhere from two to eight times the size of telescopes launched in space), ground-based telescopes can resolve images unseen by small scopes and also collect up to eight times as much light—a key capability when one is attempting to image the faintest of objects—like a planet in another solar system decamped for the southern Atacama Desert of Chile, and the Las Campanas Observatory’s Magellan Clay telescope—a 6.5 meter-diameter mounted telescope on the summit of Cerro Manqui. Because of their size (anywhere from two to eight times the size of telescopes launched in space), ground-based telescopes can resolve images unseen by smaller scopes and also collect up to 64 times as much light, a key capability when one is attempting to image the faintest of objects—like an exoplanet, a planet in another solar system.
Telescopes like Magellan are at the heart of a new technique in astronomy called “direct imaging,” in which astronomers are able to directly image exoplanets. Until recently, discoveries of exoplanets were all indirect observations—that is, inferences were made by observing the stars that these planets orbit. During the past few decades, nearly 3,000 exoplanets have been discovered, with more than two-thirds of those being detected by the Kepler space telescope. But for all of those Kepler discoveries, the planets in question have not actually been seen; they’ve been inferred by observing the shadow that they cast on the star in the system. Direct imaging is unique in that it is the only method by which an exoplanet is actually seen. Only a handful of exoplanets have been directly imaged, the first occurring during the past decade.
Follette was drawn to the doctoral program at the University of Arizona because of its access to some of the largest telescopes in the world (including Magellan); subsequently, her participation on planet-imager survey teams positioned a young grad student as a pioneer in a field that could forever alter our understanding of space.
Which takes us back to Chile. In the fall of 2014, Follette had returned for “one more observing run” while she still had access to Arizona’s telescopes. “But here’s the thing,” she says. “You rarely know whether you’ve seen anything new when you’re at the telescope. It’s not until later when you do a detailed analysis of the data that you know whether you have an interesting result.” So Follette was at Stanford in the early months of 2015 when her data revealed something never before imaged directly—an exoplanet in the process of formation.
“You have a moment of exhilaration when you think you see something interesting in your data,” she says, “but there are lots of tests to go through to be sure.” And every test confirmed her discovery. “But we didn’t think anyone would believe us until we imaged it again to prove it was still there,” she says, “and the season for observing it was already past, so we’d have had to wait at least a year.” So Follette was resigned to sit on her discovery—until she learned that another astrophysicist had also found the planet, albeit through an indirect method. “People have fairly well-founded skepticism about inferences from certain indirect detection methods—it’s probably a planet, but it could be something else,” says Follette. But in this case she had also seen the planet—literally. So the two coauthored a paper for Nature, in which they announced the birth of LkCa 15 b.
“I had spent my entire graduate career taking high-resolution images of protoplanetary transition disks, making a case that they could only be caused by planets in the process of forming,” she says. But Follette and others believed it would take the next generation of telescopes to image a planet while it was actively forming.
Until one day, she saw just that.