Pi Mensae

Pi Mensae (π Men), also known as HD 39091, is a yellow dwarf star[3] in the constellation of Mensa. This star has a high proper motion. The apparent magnitude is 5.67, which can be visible to the naked eye in exceptionally dark, clear skies. It is nearly 60 light-years away. The star is slightly larger than the Sun in terms of mass, size, luminosity, temperature and metallicity, and is about 730 million years younger. It hosts three known planets.

Pi Mensae
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Mensa
Right ascension 05h 37m 09.88684s[1]
Declination −80° 28′ 08.8346″[1]
Apparent magnitude (V) +5.65[2]
Characteristics
Spectral type G0 V[3]
U−B color index 0.11[2]
B−V color index 0.60[2]
V−R color index 0.31
R−I color index 0.29
Variable type none
Astrometry
Radial velocity (Rv)10.71±0.12[1] km/s
Proper motion (μ) RA: 310.909 mas/yr[1]
Dec.: 1,049.060 mas/yr[1]
Parallax (π)54.6825 ± 0.0354 mas[1]
Distance59.65 ± 0.04 ly
(18.29 ± 0.01 pc)
Absolute magnitude (MV)+4.35±0.01[4]
Details[5]
Mass1.11±0.01 M☉
Radius1.15±0.01 R☉
Luminosity1.532±0.004 L☉
Surface gravity (log g)4.35±0.01 cgs
Temperature6,013±18 K
Metallicity [Fe/H]0.09[6] dex
Rotational velocity (v sin i)2.96[6] km/s
Age3.4±0.6 Gyr
Other designations
π Men, CD−80° 195, CPD−80° 161, GJ 9189, HD 39091, HIP 26394, HR 2022, SAO 258421, LFT 429, LHS 208, LTT 2359, TOI-144
Database references
SIMBADdata
ARICNSdata

Planetary system

On October 15, 2001, an extrasolar planet was found orbiting the star.[7] Pi Mensae b is one of the most massive planets ever discovered, and has a very eccentric orbit that takes approximately 2,151 days (5.89 years) to complete. Because of its eccentricity, and being a massive brown dwarf that passes through the habitable zone, it would have disrupted the orbits of any Earth-like planets, and possibly 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.[8] In 2020, the true mass of Pi Mensae b was measured to be 14.1 MJ via astrometry.[9] Since this is greater than 13 Jupiter masses, the object could be considered a brown dwarf, although more recent astrometric results suggest a slightly lower mass. Pi Mensae was ranked 100th on the list of top 100 target stars for the planned (but now-canceled) Terrestrial Planet Finder mission to search for Earth-like planets.

On September 16, 2018, a preprint was posted to arXiv detailing the discovery of a super-Earth on a 6.27-day orbit around the star, the first exoplanet detection by the Transiting Exoplanet Survey Satellite (TESS) submitted for publication.[10] This was confirmed two days later, where the attention was called that the system is amenable for future planet atmospheric studies.[11]

In 2020, an analysis with Gaia DR2 and Hipparcos astrometry showed that planets b and c are located on orbits mutually inclined by 49°−131° (1 sigma), which causes planet c to not transit most of the time, and acquire large misalignments with its host star's spin axis.[12]

Planet c likely formed on a wide orbit, and then migrated inward under the gravitational influence of the planet or brown dwarf b.[13] It is likely to retain a portion of primordial, highly volatile atmosphere.[14]

In 2022, the discovery by the radial velocity method of a third planet, Pi Mensae d, on a 125-day orbit was announced.[15] Another 2022 study did not confirm this planet,[16] but a 2023 study did detect it.[17]: 24 

The Pi Mensae planetary system[10][14][15][16]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
c 3.63±0.38 M🜨 0.06839±0.00050 6.267852±0.000016 0 87.05±0.15° 2.131+0.037
−0.042 R🜨
d ≥13.38±1.35 M🜨 — 124.64+0.48
−0.52		 0.220±0.079 — —
b 12.325+1.192
−1.384 MJ		 3.311+0.134
−0.148		 2088.8±0.4 0.642+0.0007
−0.0006		 54.436+5.945
−3.719°		 —

See also

References
  1. Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  2. Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
  3. 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.
  4. Holmberg, J.; et al. (July 2009), "The Geneva-Copenhagen survey of the solar neighbourhood. III. Improved distances, ages, and kinematics", Astronomy and Astrophysics, 501 (3): 941–947, arXiv:0811.3982, Bibcode:2009A&A...501..941H, doi:10.1051/0004-6361/200811191, S2CID 118577511.
  5. Bonfanti, A.; et al. (2015). "Revising the ages of planet-hosting stars". Astronomy and Astrophysics. 575. A18. arXiv:1411.4302. Bibcode:2015A&A...575A..18B. doi:10.1051/0004-6361/201424951.
  6. Delgado Mena, E.; et al. (April 2015), "Li abundances in F stars: planets, rotation, and Galactic evolution", Astronomy & Astrophysics, 576: 24, arXiv:1412.4618, Bibcode:2015A&A...576A..69D, doi:10.1051/0004-6361/201425433, S2CID 56051637, A69.
  7. 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)
  8. Reffert, S.; Quirrenbach, A. (2011). "Mass constraints on substellar companion candidates from the re-reduced Hipparcos intermediate astrometric data: nine confirmed planets and two confirmed brown dwarfs". Astronomy & Astrophysics. 527. id.A140. arXiv:1101.2227. Bibcode:2011A&A...527A.140R. doi:10.1051/0004-6361/201015861. S2CID 54986291.
  9. 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
  10. Huang, Chelsea Xu; et al. (2018). "TESS Discovery of a Transiting Super-Earth in the π Mensae System". The Astrophysical Journal Letters. 868 (2): L39. arXiv:1809.05967. Bibcode:2018ApJ...868L..39H. doi:10.3847/2041-8213/aaef91. PMC 6662726. PMID 31360431.
  11. Gandolfi, D.; Barragan, O.; Livingston, J.; Fridlund, M.; Justesen, A. B.; Redfield, S.; Fossati, L.; Mathur, S.; Grziwa, S.; Cabrera, J.; Garcia, R. A.; Persson, V.; van Eylen, V.; Hatzes, A. P.; Hidalgo, D.; Bugnet, L.; Cochran, W. D.; Csizmadia, Sz.; Deeg, H.; Eigmueller, Ph.; Endl, M.; Erikson, E.; Esposito, M.; Guenther, E.; Korth, J.; Luque, R.; Montanes-Rodriguez, P.; Nespral, D.; Nowak, G.; Paetzold, M.; Prieto-Arranz, J. (2019). "TESS's first planet: a super-Earth transiting the naked-eye star Pi Mensae". Astronomy & Astrophysics. 619 (1): L10. arXiv:1809.07573. Bibcode:2018A&A...619L..10G. doi:10.1051/0004-6361/201834289.
  12. Xuan, Jerry W.; Wyatt, Mark C. (2020), "Evidence for a high mutual inclination between the cold Jupiter and transiting super Earth orbiting π Men", Monthly Notices of the Royal Astronomical Society, 497 (2): 2096–2118, arXiv:2007.01871, doi:10.1093/mnras/staa2033
  13. 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
  14. Huber, Daniel; et al. (2022), "A 20 Second Cadence View of Solar-type Stars and Their Planets with TESS: Asteroseismology of Solar Analogs and a Recharacterization of π Men C", The Astronomical Journal, 163 (2): 79, arXiv:2108.09109, Bibcode:2022AJ....163...79H, doi:10.3847/1538-3881/ac3000, S2CID 237259938
  15. 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
  16. 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.
  17. Laliotis, Katherine; Burt, Jennifer A.; et al. (February 2023). "Doppler Constraints on Planetary Companions to Nearby Sun-like Stars: An Archival Radial Velocity Survey of Southern Targets for Proposed NASA Direct Imaging Missions". The Astronomical Journal. arXiv:2302.10310.
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