Scientists Discover 3 New “Super-Earth” Exoplanets

In Brief

Scientists working on Kepler’s K2 mission found three exoplanets at the internal and external limits of the region around a star where rocky planets form life-sustaining atmospheres. This could be key to understanding Earth-like exoplanet evolution.

A Key to the Galaxy?

NASA’s Kepler space telescope — presently on its K2 mission — just made another major discovery, confirming the existence of three additional exoplanets. These new alien worlds orbit a star not so far away called GJ 9827, and all fall into the “super-Earth” category. The discovery was first published on the ArXiv preprint server on September 5.

As we learned in the case of 55 Cancri e, super-Earth doesn’t mean “like Earth, only better.” They’re extrasolar planets whose mass is greater than Earth’s, yet significantly less than our system’s ice giants Neptune and Uranus, which have the masses of 17 and 15 Earths, respectively (note that while though Uranus is bigger than Neptune, it is less massive). Since the category only speaks to the exoplanet’s mass, we can’t say anything about an exoplanet’s surface conditions. It’s big, but may or may not be suitable to life.

exoplanet gj 9827 kepler extraterrestrial life
Earth compared to super-Earth 55 Cancri e.  (Image credit: NASA)

To Seek Out New Worlds

The three exoplanets’ host star, GJ 9827, is 30.3 parsecs (nearly 100 light-years) away, which makes them the closest planets yet discovered by K2. Their radii, or distance from their sun, at 1.75, 1.36, and 2.1 times that of Earth, puts them on the interior and exterior limits of the distance that can sustain rocky planets. This makes them excellent candidates for atmospheric observation once space telescopes like the James Webb Space Telescope are up and running.

There’s still much to be learned about how rocky, Earth-like exoplanets evolve at different distances from their host star. These planets’ orbits span the internal and external limits of the region around a star where rocky planets form; beyond that span (roughly 1.5-times the distance between the Earth and the Sun), planets become giants. As such, these super-Earths present an excellent opportunity for us to learn the factors which cause a formerly rocky planet to grow into a hot gas giant, denying its future as a potentially-hospitable exoplanet.

It’s important to remember that more well-known planets in the TRAPPIST-1 system and orbiting Proxima b are only the most popular exoplanets because of their proximity to Earth, or most Earth-like orbits and mass(es), as far as we can tell. But in order to advance our search for life beyond the solar system, we can’t count a single new exoplanet out.

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