To date Kepler has detected about 2,740 candidate exoplanets by measuring the extremely faint dip in starlight reaching its instruments when a planet passes in front of a star. Of those, 122 plus the seven total planets counted around Kepler-62 and -69 have been confirmed by other telescopes as true exoplanets.
William Borucki of NASA’s Ames Research Center, the Kepler principal investigator, terms the spacecraft a “pathfinder” that will point the way to more detailed discoveries. Earlier this month NASA selected the Transiting Exoplanet Survey Satellite (TESS) mission as an astrophysics Explorer-class space mission.
Capped at $200 million, TESS will scan bright stars within about 30 light years of Earth to find habitable-zone planets that can be better analyzed with spectroscopy. Ultimately, the planned James Webb Space Telescope may be upgraded in space to analyze the atmospheres of some of those planets.
“That’s the edge of what we might be able to do,” Borucki said during a press conference announcing the latest Kepler discoveries. “You need a big telescope. You need a telescope that blocks out the light of a star, because it’s over a billion times brighter than a planet. That’s extremely difficult to do, to the point where you block it off so thoroughly that you can actually see the planet. Once you can do that, then you can actually do spectra and get the composition of the atmosphere.”
To date astronomers can only make educated guesses about the compositions of the exoplanets they are finding, based on similarities to other exoplanets.
While Kepler-62f probably has a rocky structure, there is a chance Kepler-62e may be a “water world,” Borucki said.
“If we look at our own ocean, it is just full of life,” he said. “Speculating as to what those oceans would be like is a puzzle, but one of the things that’s important is to get elements into that water. Some [other Kepler work involves how to] get elements from the rocky into the core to build life.”