Using data from NASAs Kepler/K2 mission and several ground-based instruments, astronomers have discovered a planetary system with three transiting planets around the 9-billion-year-old star EPIC 249893012.

An artists impression of the EPIC 249893012 planetary system. Image credit: Sci-News.com.

EPIC 249893012 is a G8-type evolved star located approximately 1,057 light-years away from Earth.

Also known as 2MASS J15125956-1643282 or TYC 6170-95-1, the star is 71% larger than the Sun, but has a mass of just 1.05 times solar.

EPIC 249893012, which is approximately 9 billion years old, hosts at least three massive planets.

The inner planet is a hot super-Earth with an orbital period of 3.6 days.

Named EPIC 249893012b, the alien world is 1.95 times bigger than Earth and 8.75 times more massive.

EPIC 249893012b is a super-Earth with a density compatible with a pure silicate composition. However, a more realistic configuration would be a nickel-iron core and a silicate mantle, said Diego Hidalgo from the Instituto de Astrofisica de Canarias and the Universidad de La Laguna, Tenerife, and his colleagues.

The planet has some residual hydrogen-helium atmosphere, which enlarges its radius but does not significantly contribute to the total planet mass.

Planets EPIC 249893012c and d are warm sub-Neptunes with orbital periods of 15.6 and 35.7 days, respectively.

They have masses and radii of 14.67 Earth masses and 3.67 Earth radii and 10.2 Earth masses and 3.94 Earth radii.

The three new planets were first discovered in data from the Kepler/K2 mission.

Hidalgo and co-authors then confirmed the discovery using the InfraRed Camera and Spectrograph (IRCS) on the 8.2-m Subaru Telescope, the High Accuracy Radial velocity Planet Searcher (HARPS) spectrograph at the 3.6-m telescope of ESOs La Silla Observatory, and the HARPS-N spectrograph at the 3.58-m Telescopio Nazionale Galileo at Roque de Los Muchachos Observatory.

Combining K2 photometry with high-resolution imaging and high-precision Doppler spectroscopy, we confirmed the three planets and determined their masses, radii, and mean densities, the astronomers explained.

Because the EPIC 249893012 system is at an early stage of its evolution after leaving the main sequence, it is a good candidate for a detailed study of its dynamical evolution to (i) shed light on the formation of close-in giant planets, and (ii) test a hypothesis that giant planets form a dynamical barrier that confines super-Earths to an inward-migrating evolution, they said.

The teams paper was published in the journal Astronomy & Astrophysics (arXiv.org preprint).

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D. Hidalgo et al. 2020. Three planets transiting the evolved star EPIC 249893012: a hot 8.8-MEarth super-Earth and two warm 14.7 and 10.2-MEarth sub-Neptunes. A&A, in press; doi: 10.1051/0004-6361/201937080

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Astronomers Find Three Massive Exoplanets Orbiting Evolved Star | Astronomy - Sci-News.com