Now, researchers at the NASA Ames Research Center at Moffett Field, Calif., have found a planet -- Kepler-22b -- that's right in that zone.
NASA finding feeds talk of a new Earth
But don't pack your bags just yet. If you traveled at the speed of light, it would take 600 years to get there.
However the news is still exciting stuff for experts such as astrophysicist Neil deGrasse Tyson of the American Museum of Natural History. The discovery, Tyson said on "The Early Show," is thrilling because of the potential for life on the planet. He explained, "In the catalogs of planets that we now have, this is the first time we've had an Earth-like planet in the habitable zone with a star. ... We're kind of biased: We're looking for life as we know it. You can imagine, I suppose, that there is life on something other than water, but that's kind of -- we don't know how to get a handle on that. We do have a handle on life -- every place there's water on Earth, there's life -- even the Dead Sea. They called it the Dead Sea because they didn't see fish. But you pull out your microscope and there's microbes everywhere on Earth."
However, it isn't likely humans are going to be guests on Kepler-22b anytime soon, particularly because our current technology has its limitations. "It's not close," Tyson said. "(With) our fastest spacecraft today, it would take something like 300,000 years to get there. ... Probably even longer."
What's the next realistic step for researchers, now that the planet's been found?
"You build the catalog of these planets that could have life," Tyson said. "Now you have a second round of observations to try to see the atmosphere, to see if the atmosphere has bio-markers for thriving life on its surface. Then you say, 'Well, if you ever have the chance to go somewhere or to target telescopes to listen for intelligent life, those will be at the top of the list."'