NASA announced the discovery of the planet by its Kepler telescope on Monday.
Scientists say the planet - named Kepler-22b - is sitting outside our solar system, smack in the middle of what astronomers call the Goldilocks zone - that hard to find place that's not too hot, not too cold, where water, which is essential for life, doesn't freeze or boil. And it has a shopping mall-like surface temperature of near 72 degrees, scientists say.
It's the first planet confirmed in the habitable zone.
"This is a phenomenal discovery in the course of human history," said Geoff Marcy of UC Berkeley, one of the pioneers of planet-hunting outside our solar system. "This discovery shows that we Homo sapiens are straining our reach into the universe to find planets that remind us of home. We are almost there."
Scientists say Kepler-22b circles a star that could be the twin of Earth's sun and at just about the same distance. The planet's year is 290 days and likely has water and rock.
But the planet is too big for life to exist on the surface. The planet is about 2.4 times the size of Earth, which means it could be more like the gas-and-liquid Neptune with only a rocky core and mostly ocean.
Still, it's exciting to image the possibilities.
"It's a great gift," said Chief Kepler scientist William Borucki. "We consider this sort of our Christmas planet."
The Associated Press contributed to this report.
