Pi Mensae (π Men), also known as "HD 39091", is a yellow dwarf star, located in the constellation Mensa. The star has a high proper motion. It has an apparent magnitude of 5.67, which means the star is visible under exceptionally dark and clear skies. The star is slightly larger than the Sun in terms of mass, size, luminosity, temperature, and metallicity. It is located about 59 light years from Earth. The star is about 730 million years younger than the Sun. The star is also confirmed to host two extrasolar planets.
Planetary system[]
On October 15, 2001, an extrasolar planet was discovered to be orbiting the star. Pi Mensae b is one of the most massive planets found so far, and has a very eccentric orbit which takes approximately 5.89 years, or 2151 days, to complete. Because of its eccentricity, and being a massive superjovian planet which passes through the habitable zone, it would have disrupted the orbits of any Earth-like planets that may be present in the system, and might have potentially thrown them into the star, or out into the interstellar medium.
Incorporating more accurate Hipparcos data yields a mass range for the companion to be anywhere from 10.27 to 29.9 times that of Jupiter, confirming its substellar nature with the upper limit of mass putting it in the brown dwarf range.
On September 16, 2018, a preprint was posted to arXiv, reporting and detailing the discovery of a Super-Earth planet in the system, on a 6.27-day orbit around the star. The planet was discovered by the Transiting Exoplanet Survey Satellite (TESS), and was the first planet to be discovered by it and submitted for publication.
| Planet | Mass | Semimajor axis | Orbital period (days) | Eccentricity | Inclination | Radius |
|---|---|---|---|---|---|---|
| b | ≥10.27 Jupiter mass | 3.38 AU | 2151 days (5.89 years) | 0.6405 | N/A | N/A |
| c | 4.82 Earth mass | 0.06839 AU | 6.2682 days | 0 | 87.27° | 2.14 Earth radius |