An artist's illustration of an Earth-like planet. The search for planets that are similar to Earth is one of NASA's main goals. Many planets have already been discovered orbiting other stars, but so far only larger planets (the size of Jupiter or larger) have been found. New missions are being planned by NASA which will be able to detect smaller Earth-sized planets. Some of these missions will also try to detect signs of life on these planets by studying emissions in their atmospheres.


The Habitable Zone

For an alien planet to house life it must be:

Close enough to its sun to receive enough energy.

Not so close to its sun that it's too hot for liquid water to exist.

This region around a star is known as the 'habitable zone'.

To learn more about: Habitable Zone , here & click here.
Stellar Ecospheres - The Habitable Zone of Stars & click here.

How Many Habitable Planets & Moons...
How Many Habitable Earths Are Out There?
How Many Habitable Planets Could Be Out There?

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