the final frontier

What super Earths mean for finding life in the galaxy

by JoAnna Wendel

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Our galaxy is full of planets orbiting countless stars, and scientists tentatively call some of them “Earth-like,” but what does that really mean?

“Super Earth” is a class of exoplanet in the size range between Earth and our solar system’s ice giants Neptune and Uranus.

So far, exoplanet-hunting endeavors like NASA’s Kepler telescope have spotted (and confirmed) more than 4,000 exoplanets.

Of these, only a small fraction are Super Earths.

But that doesn’t mean that these planets are like Earth in anything other than size.

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Earth has a special mix of active geology, surface liquid water, magnetic field, thick (but not too thick) atmosphere, and that small range of temperatures in which life as we know it can thrive.

Super Earths can orbit too close to their star, making them too hot, or too far from their star, making them too cold.

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Sometimes a star blasts a Super Earth with too much radiation.

The TRAPPIST-1 system, for example, contains seven rocky planets -- the most Super Earths orbiting a single star.

Two of these planets, TRAPPIST-1b and c, orbit too close to the star to be habitable. The farthest planet, TRAPPIST-1h, orbits too far away

Four of the planets, TRAPPIST-1d, e, f, and g, orbit within the star’s “habitable zone,” that special distance where enough heat could radiate from the star to keep a planet’s surface water liquid.

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However, even though these exoplanets orbit in their star’s habitable zone, scientists still don’t know much about their atmospheres or surfaces.

Some Super Earths are “Hot Earths,” like GJ 357 b, which is Earth-like in size and possibly rocky, but is orbiting too close to its star to maintain a life-friendly environment.

Other Super Earths, like OGLE-2016-BLG-1195 Lb, are probably too cold to harbor life.

Astronomers find more Super Earths every year. Some of them even show up in the stacks of yet-to-be-analyzed data from old missions, like the Kepler Telescope, which operated from 2009 to 2018.

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And sometime in the next couple of years, NASA will launch its highly anticipated James Webb Space Telescope, which will look even closer at exoplanets’ atmospheres to determine whether they’re suitable for life as we know it.

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