MELISSA BLOCK, HOST:
We begin this hour with an exciting new astronomy lesson - the discovery of an Earthlike planet around a distant star. It orbits in the so-called Goldilocks zone where liquid water and possibly life could exist. NPR's Geoff Brumfiel reports on this new faraway world and how it came into view.
GEOFF BRUMFIEL, BYLINE: NASA has a telescope in space called Kepler, and Kepler has just one job - to watch for very faint eclipses caused by faraway planets as they pass in front of their stars. Today, scientists announced they had seen possible eclipses from roughly 500 distant worlds.
JEFF COUGHLIN: These new 500 are kind of all types of planets. They're all over the place.
BRUMFIEL: That's Jeff Coughlin, an astronomer at the SETI Institute who works on the Kepler mission. Some of the new planets are big gas giants like Jupiter. Some are small. Some orbit near their star and get scorched, like our innermost planet, Mercury. Others are far away, icy and cold.
COUGHLIN: But 12 of them are in the habitable zone where liquid water could exist on their surface.
BRUMFIEL: And liquid water means life, as we know it, could also exist. Now, of those 12, there is one that really stands out.
COUGHLIN: Kepler-452B...
BRUMFIEL: Kepler-452B is exciting for a couple of reasons. Doug Caldwell, another astronomer on the Kepler mission, says that for one thing, it's a good size.
DOUG CALDWELL: It's about 60 percent bigger than the size of the Earth in radius.
BRUMFIEL: Its orbit is similar. One year is 385 Earth days. But maybe the most exciting thing about this planet isn't planet itself but the star it orbits.
CALDWELL: It's very similar to the Sun. It's about 20 percent brighter than the sun. But the planet 452B is slightly further away from its start than we are from the Sun, so it's actually receiving only about 10 percent more energy from its star than we're seeing from our star.
BRUMFIEL: In other words, this new planet and its star are pretty much the closest thing to Earth we've seen yet. And that's why everyone's so excited. There could be water, and that means there could be life quite similar to what we have here. Now, there are some important differences. It appears to be about five times the mass of our planet, and its also likely to be quite a bit older. The star's around 6 billion years old. That makes it 1-and-a-half billion years older than the sun.
CALDWELL: And presumably, the planet is 1-and-a-half billion years older than the Earth.
BRUMFIEL: That could be bad news for any inhabitants on 452B. As stars age, they get hotter. And the planet's hot star could be triggering a greenhouse effect on the surface.
CALDWELL: So this planet is kind of on the verge of being at that runaway greenhouse stage where it could be losing all of its water.
BRUMFIEL: In fact, our own planet will someday be in a similar pickle, says factor on will someday be in a similar pickle says Marc Kuchner, an astrophysicist at NASA's Goddard Space Flight Center.
MARC KUCHNER: There'll be drastic changes on Earth as we start losing the oceans just because of the Sun warming up a few percent.
BRUMFIEL: But Kuchner cautions that we shouldn't draw too many conclusions about our own fate from the new 452B.
KUCHNER: It's not really a peek into our future.
BRUMFIEL: That's because there are a lot of things we still don't know about this new world.
KUCHNER: Is this planet made of rocks? Is it made of some other strange material that we haven't even imagined?
BRUMFIEL: We may never be able to answer these questions. 452B is about 1,400 light years away. That's way too far to send a space probe. Even the best telescopes we could imagine would strain to see the little world at those vast distances. Nevertheless, Kuchner says, Kepler-452B is a big deal.
KUCHNER: The number of planets that are really in the range of Earth's size and really in their habitable zones is tiny, and these are precious. And this is another major discovery.
BRUMFIEL: And everyone hopes there could be even more discoveries to come. NASA's next step is to build a telescope that could search for planets around stars much closer to Earth with Earthlike worlds we might someday be able to see. Geoff Brumfiel, NPR News.
BLOCK: Additional reporting for that story came from NPR's Nell Greenfieldboyce. Transcript provided by NPR, Copyright NPR.
