Astronomers unlock the mysteries of super-Earths

A star about 100 light years away in the Pisces constellation, GJ 9827, hosts what may be one of the most massive and dense super-Earth planets detected to date according to new research led by Carnegie's Johanna Teske. This new information provides evidence to help astronomers better understand the process by which such planets form.

The GJ 9827 star actually hosts a trio of planets, discovered by NASA's exoplanet-hunting Kepler/K2 mission, and all three are slightly larger than Earth. This is the size that the Kepler mission determined to be most common in the galaxy with periods between a few and several-hundred-days.

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The Kepler spacecraft observed GJ 9827 from December 2016 to March 2017, during its Campaign 12. These observations allowed the team to discover that this nearby late K-type dwarf star is orbited by three alien worlds. The newly found planets were classified as "super-Earths" as they have masses higher than Earth's but lower than that of Solar System's gas giants.

Located some 98 light years away from the Earth, GJ 9827 is a bright star of spectral type K6V. It has a radius of about 0.63 solar radii and is approximately 15 percent less massive than our Sun. The scientists found that the star is circled by three planets, designated GJ 9827 b, c and d, located about 0.02, 0.04 and 0.06 AU from the host respectively.

 

A super-Earth is an extrasolar planet with a mass higher than Earth's, but substantially below the mass of the Solar System's smaller gas giants Uranus and Neptune, which are both more or less 15 Earth masses.

The term super-Earth refers only to the mass of the planet, and does not imply anything about the surface conditions or habitability.

Astronomers at the European Southern Observatory in Chile found out that 40 per cent of red dwarves are orbited by super-Earths. Red Dwarfs are by far the most common type of star in the Milky Way galaxy, so there might be tens of billions of such planets in our galaxy alone.