Between the vastness of space and the brightness of stars hide a plentitude of planets. But if you peer close enough at a flickering star—with a multi-billion dollar orbital telescope, granted—you might just see evidence of rocky and gaseous travelers passing in front of their stellar anchors.

After months of peering, NASA's best planet-hunting telescope Kepler just confirmed the existence of 104 more planets orbiting stars beyond the solar system. The telescope—operating in its jury-rigged, life-extending K2 mission—finds planets by measuring minuscule flickers in brightness from when the planets pass in front of their stars. Most of the planets it finds are gas giants, and unlikely to harbor anything humans would recognize as living. But four of the current batch are rocky. Though they're larger than Earth, and presumably have different chemical characteristics, these could be candidates for finding life—a search that inspires the Kepler mission scientists who discuss their work in the documentary above.

When the Kepler spacecraft launched on March 7, 2009, its mission was to look for planets in a small, fixed patch of sky. Then, between July 2012 and May 2013, two of the gyroscopic wheels used to keep the telescope properly pointed failed. Stymied by the now-listless spacecraft, NASA reached out to the space community for possible ways to keep using the craft to look for new planets. In late August, a group of engineers for Ball Aerospace figured out how to stabilize the telescope using photons from the sun. NASA gave Kepler's mission a new name: K2.

While the first Kepler mission was able to look deeply into the sky—doing what NASA characterizes as a stellar demographic survey—K2 sweeps along, glancing at whatever it passes in the course of its orbit. As such, its targets tend to be stars close to the solar system. Many of these are red dwarfs, which are the predominant star type in the Milky Way galaxy.

Neither the Kepler mission nor K2 pick out planets by themselves. The most promising flickers from K2's observations get passed along to various astronomical centers. These observatories—North Gemini telescope and the W. M. Keck Observatory in Hawaii, the Automated Planet Finder of the University of California Observatories, and the Large Binocular Telescope operated by the University of Arizona—compare K2's observations to data they've collected from Earth of the same regions. Only by comparing the two sets of observations can the candidate planets from K2 be confirmed. The 104 confirmed exoplanets in this batch come from a culled total of 197 K2 candidates. But many more wait to be found.