science -- November 4, 2013 at 6:56 PM ET
NASA finds billions of Earth-like planets, but we won't live there anytime soon
Using NASA data from the Kepler spacecraft, astronomers calculated for the first time Monday that roughly one in five stars, similar to Earth's sun, have planets about the size of Earth in the Milky Way galaxy. They exist in the habitable temperature region, known as the Goldilocks zone, where a planet is just the right distance from a star, according to the resulting study published in the journal Proceedings of the National Academy of Science.
University of California at Berkeley's Geoff Marcy, one of the study's co-authors, said that 40 billion of the 200 billion stars in the Milky Way are like our sun. Another co-author puts the number closer to 50 billion.
The researchers also cautioned that even though these Earth-like planets lie in the habitable zone, it does not mean they could support life. Slate's Phil Plait also offers a caveat:
"The planet might be the right size and distance from its star, but have an atmosphere of carbon dioxide that gives it a runaway greenhouse effect, making it a blazing hell like Venus. Or it may have a thin atmosphere which can't retain heat, making it a cold, desolate desert like Mars. Or it may have a lot of ammonia in the air, or some other noxious gas. We don't know anything yet about such contingencies. But planets like this would still be counted as Earth-like in the study here, so we need to keep that in mind."