NASA's Kepler seeks to answer: Is anybody out there?

This artist's concept illustrates Kepler-16b, the first planet known to definitively orbit two stars -- what's called a circumbinary planet. The planet was discovered by NASA's Kepler mission.
NASA/JPL-Caltech/T. Pyle

(CBS News) The question "Is anybody out there?" grows more tantalizing with the discovery of each new far-off planet. Barry Petersen has been talking to scientists searching for clues . . .

Starry nights inspire wonder, and wondering: Is there life out there?

So how fitting that, in March 2009, NASA launched the planet-hunting telescope Kepler into the night sky.

Look up tonight at the constellation Cygnus -- also known as the Northern Cross -- and up in that one slice of sky is where Kepler has been scanning 150,000 stars every 30 minutes for the last four years.

Natalie Batalha is a Kepler Mission scientist, but she's really a stargazer with a passion. "We were born to be discoverers right? I think that's basically what drives us."

She and other Kepler Mission scientists look at measurements of the brightness of a star. "When the planet passes in front, it's going to block some of the light," Batalha explained.

That momentary dimming of light is how we infer the existence of a plane orbiting that star.

"There's not much more dramatic to discover than another world," said Petersen.

"Another world like ours," because it changes the way we look at the cosmos, right?" said Batalha.

An artist's impression of a world known as Kepler-62f, orbiting its parent sun at a distance that would allow water to exist as a liquid on its surface. NASA

Luke Skywalker's fictional planet of Tatooine had two suns. Kepler one-upped the makers of "Star Wars," finding REAL planets with two suns.

"Sometimes science informs science fiction, and sometimes science fiction informs science, right?" said Batalha.

Hard to believe . . . but despite the hundreds of trillions of stars in the universe, it wasn't until 1995 that scientists were 100 percent sure they'd found a planet beyond our solar system.

Since then, more than 800 planets have been found, including 122 confirmed by Kepler.

Some are freezing cold -- think Neptune, at -360 degrees Fahrenheit.

Some are scalding hot -- think Mercury, which can reach 800 degrees F.

But the real hunt is for what scientist call "Goldilocks" planets -- not too hot, not too cold -- making them a lot like Earth.