Rocky Super-Earth Found Orbiting Solar-Type Star

The newfound exoplanet, named HD 285181b, is about 1.6 times bigger than Earth and 6.5 times more massive.

With a bulk density of 8.84 g/cm3, the planet is consistent with an Earth-like rock/iron composition.

It orbits HD 285181 (also known as EPIC 247418783 and 2MASS 05054699+2132552), a star about 0.9 times the size and the mass of the Sun.

HD 285181b has an orbital period of 2.23 days and is much closer to the parent star than our planet is to the Sun.

The alien world was first detected using data from NASA’s extended Kepler/K2 mission.

Its existence was then confirmed using measurements from the HIRES (High Resolution Echelle Spectrometer), an instrument mounted on the Keck Observatory’s 10-m telescope at Mauna Kea in Hawaii, and the HARPS-N (High Accuracy Radial velocity Planet Searcher for the Northern hemisphere) instrument at the 3.6-m Telescopio Nazionale Galileo in the Canary Islands.

HD 285181b currently has no substantial atmosphere.

If it existed in the past, such an atmosphere was likely eroded away by a process called photoevaporation during the first billion years of the host star’s lifetime.

“HD 285181b’s lack of a substantial volatile envelope could be explained by atmospheric loss,” said University of California, Santa Cruz astronomer Molly Kosiarek and colleagues.

“For lower mass planets experiencing a large amount of stellar insolation, photoevaporation (hydrodynamic escape) is the dominant atmospheric loss process.”

“Photoevaporation occurs when high energy photons from the host star ionize and heat the atmosphere causing it to expand and escape.”

“HD 285181b may have formed as a sub-Neptune with a substantial volatile envelope and transitioned across the Fulton gap to a super-Earth planet through photevaporation.”

The discovery will be reported in a paper in the Astronomical Journal.

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