An international team of astronomers has discovered a hot rocky and a warm puffy super-Earth exoplanets orbiting the 7.5-billion-year-old star HD 15337.
An artist’s conception of the HD 15337 planetary system. Image credit: Sci-News.com.
HD 15337, also known as TOI-402 or TIC-120896927, is a bright K1-type dwarf located about 146 light-years away from Earth.
The star is 14.9% less massive and about 16% smaller than the Sun.
With an effective temperature of approximately 8,800 degrees Fahrenheit (about 4,900 degrees Celsius), HD 15337 is a low activity star like our Sun.
Named HD 15337b and c (TOI-402b and c), the new planets orbit their star every 4.76 and 17.18 days.
They were first detected by NASA’s TESS (Transiting Exoplanet Survey Satellite) mission.
Their existence was then validated using data from the HARPS (High Accuracy Radial velocity Planet Searcher) spectrometer on ESO’s 3.6-m telescope in La Silla, Chile.
“We found that one planet is a hot rocky Super-Earth and the other one a warm puffy Super-Earth,” said University of Geneva astronomer Xavier Dumusque and colleagues.
According to the team, HD 15337b is about 1.7 times the size of Earth and 7.2 times more massive. This suggests that the planet is made primarily of rock.
HD 15337c is 2.52 times the size of our planet and 8.8 times as massive. It hosts a think atmosphere dominated by primordial hydrogen.
“Although having rather similar masses, the radius of these two planets are really different, putting them on different sides of the radius gap (also known as Fulton gap),” the astronomers said.
“With stellar irradiation 160 times more important than Earth for HD 15337b and only 29 times more for HD 15337c, it is likely that photoevaporation is at the origin of this radius difference.”
“These two planets, being in the same system and therefore being in the same irradiation environment are therefore extremely important to perform comparative exoplanetology across the evaporation valley and thus bring constraints on the mechanisms responsible for the radius gap.”
The team’s work will be published in the journal Astronomy & Astrophysics.
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X. Dumusque et al. 2019. A hot rocky and a warm puffy super-Earth orbiting TOI-402 (HD 15337). A&A, in press; arXiv: 1903.05419
