On a cold, clear night in January, Massachusetts Institute of Technology astrophysicist George Ricker and his students stepped onto a rooftop on campus and aimed a camera at the highest point in the sky.
That camera, an engineering model of the four being launched with NASA's TESS mission, revealed a night so thick with stars that they obscured the normally distinct constellations.
"In two seconds you could see things that were a hundred thousand to a million times fainter than what you could see with your naked eye," said Ricker, the mission's principal investigator.
The test offered a small taste of what TESS, the Transiting Exoplanet Survey Satellite, will discover after it launches, which could occur as soon as Monday afternoon. The spacecraft will scan almost all of the sky for neighboring stars, searching for the dips in their brightness that signal the presence of a planet.
The goal: to find planets that are smaller than Neptune, with a radius less than about four times that of Earth. Scientists will then use other telescopes to measure the masses of 50 of them.
A few of the worlds TESS finds may be small, rocky bodies, like Earth. And a few of those might, just possibly, be habitable places for life as we know it.
"It's very exciting," Ricker said. "We're getting a chance to potentially answer a question that humanity's always been interested in: What's in the sky? And are there other beings, other places like Earth?"
Astronomers have been searching for planets beyond our solar system for decades.
Some of their first discoveries were confirmed in the 1990s. Among them were exoplanets that were detected by ground-based telescopes that looked for the periodic wobble in a star's motion caused by a planet's tiny tug -- a technique known as the radial velocity method. Others were found by searching for variations in the predictable rhythms of pulsars.
About 325 exoplanets had been discovered by the time NASA launched the Kepler Space Telescope in 2009. It employed the transit method, staring deep into a patch of sky and looking for the shadows cast by planets as they crossed in front of their host stars.