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NGC7635 Outside of the Milky Way, scientists estimate there are 70 sextillion stars—that’s a 7 followed by 22 zeros! (NASA)

The Planet Hunters

Experts say aliens are out there—and they are determined to find them

Fact: Aliens are real. (Well, probably.)

For centuries, people have looked into the night sky and wondered if anyone was looking back at us. And for some scientists who study space, called astronomers, that’s their job. Yep, astronomers at the National Aeronautics and Space Administration (NASA) get to look for aliens all day, every day. (Cool, huh?)

Though we haven’t met any aliens yet, experts are becoming more and more convinced that we will—soon. “We know now that we’re not alone,” says Steve Howell, a NASA astronomer. “We are finding so many planets roughly the size of [Earth]. It’s just a matter of time.”


Astronomers say that our universe is so big, there are bound to be other forms of life somewhere. OK, so just how big is outer space, anyway?

Think about it this way: Earth is part of a solar system of eight planets that orbit, or revolve around, the sun. Our sun is just one star out of the more than 200 billion stars in a galaxy called the Milky Way. To give you an idea of how big that is, imagine if our entire solar system— including Earth, the seven other planets, and the sun—were the size of a quarter. Compared with the quarter, the whole Milky Way would be the size of the United States.

Of course, it doesn’t end there. Outside of the Milky Way, scientists estimate there are 70 sextillion stars—that’s a 7 followed by 22 zeros, which equals more stars than there are grains of sand on every beach and desert on Earth. Many of these stars have their own groups of planets orbiting them.


Astronomers can now see farther into space than ever before, thanks to some very high-tech tools. In 2009, NASA launched Kepler, a spacecraft that orbits the sun in search of distant planets. Kepler, named after a famous 17th-century astronomer, has a powerful telescope focused on a field of stars in the northern sky. So far, it has found 3,000 possible planets.

Every six seconds, Kepler takes a picture of the stars. Once a month, Kepler sends its data back to the scientists on Earth. As part of the Kepler Mission Team, Howell closely studies the data. The team is looking for certain telltale signs of planets. For instance, if a star looks like it’s “wobbling,” it could mean that the star is being tugged back and forth by a planet’s gravity. Another sign is a change in a star’s light. When a planet passes in front of its star, the star’s brightness dims. This change can help astronomers measure a planet’s size.

In December 2011, astronomers made an awesome discovery. They spotted a planet, which they call Kepler 22b, orbiting its star at just the right distance for life—not too close and not too far. This means water could exist on the planet and temperatures there could support life. Planet hunters everywhere celebrated, but they haven’t started packing quite yet. The planet is 600 lightyears away, or about 3.5 quadrillion miles (to be exact, it’s 3,527,175,223,910,165 miles away).

To figure out for sure if a planet is habitable, scientists need to study its atmosphere, the layer of gases that blocks its star’s rays. There is no way of measuring it from such a distance—yet.

Each discovery Howell’s team makes brings us closer to finding another planet just like ours, with water and living things. Of course, we don’t know what the “living things” will be like—they could be as simple as a single cell or as complex as a human being. But Howell believes that we will find another Earthlike planet during your lifetime.

Are you ready?

This article originally appeared in the February 2013 issue of Storyworks. For more from Storyworks, click here.


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