Pi Mensae b (π Men b, π Mensae b), also known as HD 39091 b, is an extrasolar planet[3] approximately 60 light-years away in the constellation of Mensa. The planet was announced orbiting the yellow main-sequence star[4] Pi Mensae in October 2001.

Pi Mensae b
Discovered byJones et al.[1]
Discovery siteAustralia Anglo-Australian
Discovery date15 October 2001
Doppler spectroscopy
Orbital characteristics[2]
5.719 ± 0.001 years (2,088.86 ± 0.37 d)
StarPi Mensae
Physical characteristics[2]

Detection and discovery


On October 15, 2001, a team of astronomers including Jones, Butler, Tinney, Marcy, Penny, McCarthy, Carter, and Pourbaix announced the discovery of one of the most massive extrasolar planets that have yet been observed. It was discovered by the Anglo-Australian Planet Search team, using a Doppler spectrometer mounted on the Anglo-Australian Telescope.

Physical characteristics


Pi Mensae b has a very eccentric orbit and takes 5.72 years to revolve around the star. The semi-major axis of the planet's orbit around the star is 3.31 AU. This planet passes through the star's habitable zone at periastron (1.19 AU) while at apastron, it passes to around Jupiter-Sun distance (5.44 AU). The gravitational influence of this planet would disrupt the orbit of any potentially Earth-like planet.[2][5]

Pi Mensae b is over ten times more massive than Jupiter,[6] the most massive planet in the Solar System. It will have 10 times the surface gravity of Jupiter alone and could be incandescent (glowing).[citation needed]

In 2020, the true mass of Pi Mensae b was measured to be 14.1 MJ via astrometry. Since this is greater than 13 Jupiter masses, the object could be considered a brown dwarf.[7] The most recent astrometric results as of 2022 have revised this mass estimate slightly downward, to 12.3 MJ.[8][2]

The plane of orbit of Pi Mensae b is strongly inclined to equatorial plane of the star, with the misalignment equal to 24±4.1°.[9]

See also



  1. ^ Jones H., Vogt S., Butler P., Marcy G., Fischer D., Pourbaix D., Apps K., & Laughlin G.
  2. ^ a b c d Feng, Fabo; Butler, R. Paul; et al. (August 2022). "3D Selection of 167 Substellar Companions to Nearby Stars". The Astrophysical Journal Supplement Series. 262 (21): 21. arXiv:2208.12720. Bibcode:2022ApJS..262...21F. doi:10.3847/1538-4365/ac7e57. S2CID 251864022.
  3. ^ Butler; et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal. 646 (1): 505–522. arXiv:astro-ph/0607493. Bibcode:2006ApJ...646..505B. doi:10.1086/504701. hdl:2299/1103. S2CID 119067572.
  4. ^ Gray, R. O.; et al. (July 2006). "Contributions to the Nearby Stars (NStars) Project: spectroscopy of stars earlier than M0 within 40 pc-The Southern Sample". The Astronomical Journal. 132 (1): 161–170. arXiv:astro-ph/0603770. Bibcode:2006AJ....132..161G. doi:10.1086/504637. S2CID 250741593.
  5. ^ "HD 39091". hzgallery.org. Retrieved 4 September 2022.
  6. ^ Jones; et al. (2002). "A probable planetary companion to HD 39091 from Anglo-Australian Planet Search". Monthly Notices of the Royal Astronomical Society. 333 (4): 871–875. arXiv:astro-ph/0112084. Bibcode:2002MNRAS.333..871J. doi:10.1046/j.1365-8711.2002.05459.x. S2CID 7583247. (web Preprint)
  7. ^ Damasso, M.; et al. (2020), "A precise architecture characterization of theπMensae planetary system", Astronomy & Astrophysics, 642: A31, arXiv:2007.06410, Bibcode:2020A&A...642A..31D, doi:10.1051/0004-6361/202038416, S2CID 220496034
  8. ^ Hatzes, Artie P.; et al. (2022). "A Radial Velocity Study of the Planetary System of π Mensae: Improved Planet Parameters for π Mensae c and a Third Planet on a 125 Day Orbit". The Astronomical Journal. 163 (5): 223. arXiv:2203.01018. Bibcode:2022AJ....163..223H. doi:10.3847/1538-3881/ac5dcb. S2CID 247218413.
  9. ^ Kunovac Hodžić, Vedad; Triaud, Amaury H M J.; Cegla, Heather M.; Chaplin, William J.; Davies, Guy R. (2021), "Orbital misalignment of the super-Earth π Men c with the spin of its star", Monthly Notices of the Royal Astronomical Society, 502 (2): 2893–2911, arXiv:2007.11564, doi:10.1093/mnras/stab237