Francesco Pepe leans over a large black chest in the basement of the Geneva Observatory. He lifts the lid to reveal a length of rubbery fiber-optic cable coiled along the bottom and surrounded by steep cliffs of foam. ”I think they may have gone a little overboard with the packaging,” Pepe says.
Dwarfed by its container, the cable doesn’t look that impressive, but it will soon be a key component in the hunt for planets like our own. In just a few months, astronomers will use the fiber to feed starlight into a new detector—the High Accuracy Radial velocity Planet Searcher–North (HARPS-N), an ultra-precise spectrograph that is being assembled nearby, not far from a field of grazing horses.
In the coming months, Pepe, an astronomer, and his colleagues will take apart the go-cart–size instrument, box up the pieces, and put them together again in a room near Italy’s Telescopio Nazionale Galileo on La Palma, one of the Canary Islands.
When HARPS-N begins observations in April, astronomers expect it will be the most precise planet hunter in the northern hemisphere. They also reckon it will be particularly well placed to help bag the most coveted extrasolar quarry of all—planets small enough to have rocky surfaces and cool enough to have liquid water. The -reason? HARPS-N will not be working alone. It will view a particular patch of the sky that has been the singular focus of NASA’s Kepler telescope for almost three years.
Kepler, which trails behind Earth in a solar orbit all its own, is on the hunt for the subtlest of flickers—periodic dips in stellar brightness caused by planets that pass, or ”transit,” in front of their host stars and briefly block about 0.01 percent of the light. And by all accounts, the spacecraft’s dogged focus on a single region of the sky has paid off nicely. In December, Kepler’s astronomers announced the discovery of a planet orbiting far enough from its sun-like host to be able to boast liquid water.
With a little luck and enough time, Kepler will find many more such planets, some quite similar in size to Earth.