Institute of Astrophysics and Space Sciences (IA) | 2018 Mar 28
A team of astronomers from 11 countries, led by researchers at the Instituto de Astrofísica e Ciências do Espaço (IA), were able to determine the precise mass of two small exoplanets orbiting the variable star HD 106315.
These two planets were previously detected by the Kepler satellite (NASA) with the transit method, which allowed researchers to determine the diameter of the planets. HD 106315b has a period of 9.5 days and a diameter of 2.44 times the diameter of the Earth, while HD 106315c has an orbital period of about 21 days, and a diameter 4.35 times the diameter of the Earth.
But to characterize a planet (for example, to determine if it is gaseous or rocky, or whether they have an atmosphere), researchers also need to know the mass of the planet, measured by the radial velocities, so that together with size, they can infer its density. ...
Using data from a large observing program with the HARPS spectrograph (ESO), the IA team estimated the mass of the smaller planet HD 106315 b to be 12.6 times that of the Earth, and the density to be 4.7 g/cm3. For the larger planet, HD 106315 c, the derived mass is 15.2 times that of the Earth, with a density of 1.01 g/cm3. These values indicate that planet “c” has a thick hydrogen-helium envelope, while a detailed investigation of planet “b”, using planetary interior models, indicates at up to 50% of rocky material and 9 - 50% of water, making it a water world.
Precise Masses for the Transiting Planetary System HD 106315 with HARPS - S.C.C. Barros et al
- Astronomy & Astrophysics 608:A25 (Dec 2017) DOI: 10.1051/0004-6361/201731276
arXiv.org > astro-ph > arXiv:1709.00865 > 04 Sep 2017