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NASA's Space Place

Earth’s Cousin

Katie McKissick
National Aeronautics and Space Administration

Since it’s always nice to make new friends, NASA is on the lookout for exoplanets. These are planets outside our solar system. They orbit a faraway star or float freely between stars.

We’re especially curious about planets similar to Earth. In our vast universe, with countless galaxies, stars, and planets, are there other planets like our own? Do they have living things we could never imagine? Are there other intelligent living things that are looking for us as we are looking for them?

We don’t know! But we’d sure like to find out.

The Kepler mission could possibly find such an exoplanet someday. The Kepler spacecraft orbits our sun just like Earth does. It scans the starry skies for faraway planets. It looks for distant stars that decrease in brightness as planets pass in front of them. So far Kepler has found 4,696 possible planets. Of those, 1,030 are definitely planets. Some of them are enormous gas giants like Jupiter, and some of them are small rocky planets like Earth.

In July of this year, Kepler made a really amazing discovery. It found a nearly Earth-sized planet orbiting a nearly sun-like star in the habitable zone. That’s the sweet spot in a solar system. The habitable zone is the distance from a star where a planet might be the right temperature to have living things. Earth sits in the habitable zone of our own star, the sun.

This newly discovered planet is named Kepler-452b It’s named after the star it orbits, which we call Kepler-452. Planet Kepler-452b is about one and a half times bigger than Earth, and it’s probably rocky like Earth is. One year on Kepler-452b lasts 385 days, just a little bit longer than a year here on Earth. The star it orbits is bigger, brighter, and older than our sun is. That means the planet is older too. Could there be life there?

It’s hard to say. Kepler-452b is 1,400 light-years away. That means it takes light, which travels staggeringly fast, 1,400 years to get there. It also means that any communications between the planets would take 1,400 years to be received. So we won’t be sending any text messages to Kepler-452b just yet. But we’ll be watching from afar.

Want to know more about exoplanets? Read about the “lone planet,” a Jupiter-sized planet without a star at NASA Space Place: http://spaceplace.nasa.gov/lone-planet.

This artist's concept compares Earth (left) to the new planet, called Kepler-452b, which is about 60 percent larger in diameter. Credits: NASA/JPL-Caltech/T. Pyle


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