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Are there any planets outside of our solar system?
Heres how the ancient Greek mathematicianMetrodorus(400-350 B.C.)
About 2,000 years later, in the 16th century, the Italian philosopherGiordano Brunosuggested something similar.
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NASA Video: Animation of a exoplanet transiting its star.
Scientists now know that both Metrodorus and Bruno were essentially correct.
Today,astronomers like meare still exploring this question, using new tools.
That evidence is based on the discoveries made by theKepler space telescope, launched by NASA in 2009.
For four years, the telescope stared continuously at a single region of space within theconstellation Cygnus.
Artist illustration of NASAs Kepler space telescope.
In that one region, the telescope detected more than 150,000 stars.
About every half-hour it observed the amount of light radiating from each star.
Back here on Earth, a team of Kepler scientists analyzed the data.
For most stars, the amount of light stayed pretty much the same.
These drops in brightness happened at regular intervals, like clockwork.
This event when a planet passes between a star and its observer is known as atransit.
And that means that in that one speck of space the Kepler telescope found 3,000 planets.
Thats because their orbits never blocked the light as seen by Kepler.
After all, planetary orbits arent all the same; theyre randomly oriented.
This discovery has revolutionized astronomy and our view of the universe.
But remember: The universe holds up to 2 trillion galaxies.
And each galaxy contains tens or even hundreds of billions of stars.
Some of those planets are gas giants, likeJupiterin our solar system.
Others are boiling hot, likeVenus.
Others may bewater worldsorice planets.
And some are Earth-like.
They found approximately50% of Sun-like stars in the Milky Wayhost an Earth-like planet in the habitable zone.
That adds up tobillions of potentially habitable worldsjust in our galaxy.
Could life exist elsewhere?
That would be as surprising as a large field containing a single stalk.
When will humans detect life elsewhere?
Will it be intelligent life?
Will people ever receive a message from another civilization?
Today, hundreds of scientists around the world are trying to answer those questions.
Hello, curious kids!
Do you have a question youd like an expert to answer?
And since curiosity has no age limit adults, let us know what youre wondering, too.
We wont be able to answer every question, but we will do our best.
