Orbital analysis of π Mensae system updates parameters for three potential exoplanets

Star system: Pi Mensae | Distance from the Sun: 59.6 light years

The π Mensae star system, which hosts the first exoplanet detected by the Transiting Exoplanet Survey Satellite (TESS), has been the subject of a comprehensive new study. By combining six years of TESS photometry — the measurement of a star's brightness over time to detect dips caused by orbiting planets — with 22 years of radial velocity data, which tracks the tiny wobbles in a star’s motion caused by a planet’s gravitational pull, this research provides the most precise orbital information to date for the planets in this system.

The research focused on updating the orbital ephemerides, or the calculated positions of the planets over time, for planets π Mensae b and c. The findings significantly reduced the uncertainty in the orbital period of π Mensae c, a sub-Neptune planet located near a critical radius gap where planets often lose their primary hydrogen and helium atmospheres. The results suggest the planet may retain heavier compounds like water and carbon dioxide.

Furthermore, the analysis supports the presence of a third potential planet, π Mensae d. The researchers estimated the mass of this third candidate to be between 13.4 and 20 times the mass of Earth. These refined measurements are crucial for understanding how the system evolved and for planning future detailed atmospheric observations using the James Webb Space Telescope.

Key findings
- Orbital period precision for π Mensae c improved by an order of magnitude.
- Radial velocity data confirms consistency with the existence of a third planet, π Mensae d.
- The mass of π Mensae d is estimated to be between 13.4 and 20 Earth masses.
- π Mensae c is identified as an ideal target for future transmission spectroscopy.

Scientific study

TESS Photometry and Radial Velocity Analysis of the sub-Neptune Exoplanet π Mensae c and the Wider π Mensae Planetary System (external link)