Then other telescopes will fill in the details. TESS is specialized to detect planets, not to reveal much about their nature. But TESS will launch right around the same time as the James Webb Space Telescope (JWST), the supersized successor to Hubble. “We’ve designed the mission to find the best targets for JWST,” Latham says. TESS’ big brother will have the power to measure the temperature and composition of many of the TESS planets — even to monitor their weather.
Meanwhile, enormous ground-based observatories like the Giant Magellan Telescope in Chile and the Thirty Meter Telescope in Hawaii, both scheduled to open their eyes around 2020, will perform the more time-consuming work of measuring the masses and densities of the planets found by TESS to determine whether they are rocky objects, gassy ones, or something else entirely.
Sniffing Out Life
“What we really want to do is image planets directly. We want to find the ones that are truly like Earth, and we know how to do it now,” says Sara Seager of MIT, a member of the TESS science team and recent recipient of a MacArthur Genius Grant. That is what NASA’s Exoplanet Direct Imaging Mission Concepts program is all about.
The idea is to blot out the light of a star and zero in on a small planet, right next to it in the sky and 10 billion times fainter (at visible wavelengths) than it. This technology “has come far — and it’s kind of unknown to the world just how far,” Seager says. The plan she is working on calls for a two-part instrument, a space telescope and an “external occulter,” a movable starshade that flies in front of the telescope to block out the starlight and bring the planet into view. Four parts of a prototype starshade are being built and will soon undergo testing. A competing team is refining an alternative approach, called an internal coronagraph, which blots out starlight from inside the telescope. Full reports on both designs are due in January 2015. NASA will then consider spending $1 billion, about $100 million a year, on the winning design.
(That’s no more expensive than other kinds of government functions that routinely get funded without anyone ever noticing: the Congressional Binding and Printing account, to pick just one example. High-profile projects like seeking out other Earths may seem expensive, but they consume a minuscule portion of government spending and deliver an outsize return in education and scientific inspiration.)
Seager is so obsessed with those other Earths, she can almost smell them. In fact, smelling them is precisely what she wants to do. Direct imaging would make it possible to analyze light from the planet’s atmosphere and “sniff” its composition spectroscopically. “What kinds of molecules provide the best signature of life? That’s the other big thing I’m thinking about now,” she says. In a new paper she studies dimethyl sulfide and chloromethane, compounds that result from the breakdown of organic material, as promising targets.
“We’d like to find 500 planets and go, oh my God, 75 percent of them show some weird gas, so we can say, statistically, we believe there is life in our solar neighborhood,” Seager says. Finding swamp gas on an alien world would be a lot less dramatic than hearing radio beeps from E.T., she concedes, but the message would be shocking all the same: We are surrounded by a living universe.
[This article originally appeared in print as "Meet the New Planet Hunters."]