What makes a planet potentially habitable

By Ashley Strickland, CNN

Updated 5:27 PM ET, Mon November 11, 2019

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This artist's concept illustration shows an exoplanet with two moons orbiting within the habitable zone of a red dwarf star.
Photos: Weird and wonderful planets beyond our solar system
This artist's concept illustration shows an exoplanet with two moons orbiting within the habitable zone of a red dwarf star.
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This is an artist's illustration of two exoplanets colliding in a binary star system.
Photos: Weird and wonderful planets beyond our solar system
This is an artist's illustration of two exoplanets colliding in a binary star system.
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This is an artist's illustration of a Neptune-type exoplanet in the icy outer reaches of its star system. It could look something like a large, newly discovered gas giant that takes about 20 years to orbit a star 11 light years away from Earth.
Photos: Weird and wonderful planets beyond our solar system
This is an artist's illustration of a Neptune-type exoplanet in the icy outer reaches of its star system. It could look something like a large, newly discovered gas giant that takes about 20 years to orbit a star 11 light years away from Earth.
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This image shows a comparison of red dwarf star GJ 3512 to our solar system, as well as other nearby red-dwarf planetary systems.
Photos: Weird and wonderful planets beyond our solar system
This image shows a comparison of red dwarf star GJ 3512 to our solar system, as well as other nearby red-dwarf planetary systems.
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This artist's illustration showcases exoplanet K2-18b orbiting its host star. It's currently the only super-Earth exoplanet that has water vapor in its atmosphere and could be within the right temperature to support life.
Photos: Weird and wonderful planets beyond our solar system
This artist's illustration showcases exoplanet K2-18b orbiting its host star. It's currently the only super-Earth exoplanet that has water vapor in its atmosphere and could be within the right temperature to support life.
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This is an illustration of an exomoon losing mass as it's being pulled around the gas giant it orbits.
Photos: Weird and wonderful planets beyond our solar system
This is an illustration of an exomoon losing mass as it's being pulled around the gas giant it orbits.
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An illustration shows what the orbit of exoplanet HR 5183 b would look like if it was dropped down in our solar system. It would likely swing from the asteroid belt to out past Neptune, the eighth planet in our solar system.
Photos: Weird and wonderful planets beyond our solar system
An illustration shows what the orbit of exoplanet HR 5183 b would look like if it was dropped down in our solar system. It would likely swing from the asteroid belt to out past Neptune, the eighth planet in our solar system.
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At least two giant planets, aged 20 million years at most, orbit the Beta Pictoris star. A disk of dust and gas surrounding the star can be seen in the background.
Photos: Weird and wonderful planets beyond our solar system
At least two giant planets, aged 20 million years at most, orbit the Beta Pictoris star. A disk of dust and gas surrounding the star can be seen in the background.
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This is an artist's interpretation of what super-Earth GJ 357 d might look like. It lies within the habitable zone of its star which is 31 light-years from Earth.
Photos: Weird and wonderful planets beyond our solar system