An Exo-What...?

Simply put, an exoplanet is a planet that orbits another star. That said, just because a planet orbits a star (like Earth) does not mean that it is automatically stable for life. The planet must be within the habitable zone, which is the area around a star in which water has the potential to be liquid…aka not so close that all the water would evaporate, and not too far away where all the water would freeze.

Recently, with the help of our Kepler spacecraft, scientists have discovered the most Earth-like exoplanet ever, Kepler-452b. Pretty cool! This chart shows 12 other exoplanet discoveries that are less than twice the size of Earth, and live in the habitable zone of their host star. Kepler-452b is special because all previous findings have orbited stars that are smaller and cooler than Earth’s.

You may be thinking, “Okay, so what? There’s an Earth-like planet that spins around a similar sized sun.” Well, Kepler-452b orbits its sun at nearly the same distance from its star as Earth does from our sun, which means that conditions on the plant could be similar to those here on Earth!

We can already guess your next question…”When are we going to Kepler-452b?!” Well, this planet is located in the constellation Cygnus which is 1,400 light-years away, so not anytime soon. However, our Kepler spacecraft continues to search for Earth-like exoplanets and gather important scientific information about them.

Here’s an artist’s comparison of Earth and the newly discovered Earth-like planet Kepler-452b. Kepler-452b is a real dud of a name, so I’m going to refer to the planet as Henrietta* for the rest of this post.

Here’s what we know:

  • Henrietta is 60% larger than Earth, so its gravity is twice as strong
  • A year on Henrietta is 385 earth days
  • It’s a bit farther away from its sun, but its sun is larger and hotter. That means Henrietta orbits in a sweet spot – a region of space that is not too hot and not too cold – the kind of place that could foster life.
  • Henrietta’s star is in the Cygnus constellation, about about 1,400 light years away from Earth

“Exoplanets, especially small Earth-size worlds, belonged within the realm of science fiction just 21 years ago,” the NASA statement says. “Today, and thousands of discoveries later, astronomers are on the cusp of finding something people have dreamed about for thousands of years — another Earth.”

Scientists don’t know if [Henrietta] could be habitable. Aside from not knowing what the planet’s composition is, they also don’t know what its atmosphere might be like.

“This is the beginning of a very long journey,” said Didier Queloz, a professor of astrophysics at Cambridge University.

*There’s no official approval of this name, but if you know someone at the IAU, pass it along.


The Kepler Space Telescope has discovered the first planet similar in size to the Earth that is also in the potentially habitable zone of a star like the sun, NASA announced today. Kepler-452b rotates once around its star every 385 days some 1,400 light-years away from Earth in the constellation Cygnus. 

The planet, scientists say, has a better than even chance of being rocky and has an orbit the right distance from its star for liquid water to exist on the surface, a necessary prerequisite for life as we know it. See image captions below. Learn more here. 

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