STEVE INSKEEP, host:
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Consider this as a summer vacation spot, the constellation Libra. That collection of stars contains a newly discovered planet. It's small and rocky, and it has mild temperatures like Earth. Scientists say this is the first planet outside of our solar system that could be home to liquid water, and maybe even life.
NPR's Nell Boyce has more.
NELL BOYCE: Our sun has eight planets, well, nine if you count Pluto. But astronomers have found dozens and dozens of planets that are orbiting other stars.
Professor MICHEL MAYOR (Astronomy, University of Geneva): We have discovered more than 100 planets here in Geneva.
BOYCE: Michel Mayor is a planet hunter at the University of Geneva. He says almost all of these planets are giant balls of gas, like Jupiter. These massive planets are relatively easy to find. They have a gravitational pull that makes their stars wobble. When scientists see that wobble, they know there is a planet. But small, rocky planets cause less of a wobble, making them harder to find.
Still, Mayor and his colleagues have had some luck using a big telescope in Chile. They pointed it at a nearby star called Gliese 581 in the constellation Libra.
Prof. MAYOR: It's one of our closest neighbors in the galaxy.
BOYCE: Mayor says his team has found three planets around this star. One of them is particularly interesting. They think the planet is a little bigger than Earth. It orbits very close to its star. Now, this star is much dimmer and cooler than our sun, so the planet isn't super hot. In fact, average temperatures are around 32 to 104 degrees Fahrenheit. Mayor says that's a friendly environment for liquid water and maybe even life.
Prof. MAYOR: We do not have any reason to believe that life exists on that planet. We can only say that we have the temperature to permit the development of life.
BOYCE: A report on the discovery has been submitted to the journal Astronomy and Astrophysics, and other experts agree that it's a significant find. Alan Boss is a planetary scientist at the Carnegie Institution of Washington.
Mr. ALAN BOSS (Planetary Scientist, Carnegie Institution of Washington): This seems to be the first discovery of an Earth-like planet. It's not exactly an Earth, but it's close enough that I think it does deserve the title of perhaps the first Earth-like planet.
BOYCE: In many ways, though, it's a mystery.
Mr. BOSS: We do not know what the composition of the planet is, and so we're just guessing it's primarily made out of rock and iron like the Earth is. We do not know how much water it may or may not have on it.
BOYCE: Boss says we could learn a lot more if researchers launched a space telescope that's specially designed to look at faraway planets. NASA has one in development, but it has been delayed indefinitely by budget woes. Still, some scientists do have a mental picture of this place. Todd Henry is an astronomer at Georgia State University. He says, if you were standing on this planet and looked up, its sun would appear to be huge, five times bigger than our sun looks to us.
Professor TODD HENRY (Astronomy, Georgia State University): So it's going to look very different in this sort of alien situation that we're in and what we're used to here on Earth. I mean, the star itself is actually going to look sort of the color of Mars, sort of a red, ruddy color.
BOYCE: He says the star is also notable because the Geneva team has found those two other planets that are circling it. They are also relatively small.
Mr. HENRY: This is starting to look like a solar system we're familiar with. If you were in a spaceship and you flew into this system, this is one of the most interesting ones there is out there now.
BOYCE: But don't count on visiting anytime soon. Even though Gliese 581 is relatively close by, it would take 20 years to get there if we could travel at the speed of light, which we can't.
Nell Boyce, NPR News.
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