HD 85512

HD 85512 is a solitary K-type main-sequence star 36.8 light-years (11.3 parsecs) away in the constellation Vela. It is about 1 billion years older than the Sun. It is extremely chromospherically inactive, only slightly more active than Tau Ceti. It exhibits a long-term variability[2] and was thought to host one low-mass planet, although this is now doubtful.[6]

HD 85512
Observation data
Epoch J2000      Equinox J2000
Constellation Vela
Right ascension 09h 51m 07.05180s[1]
Declination −43° 30′ 10.0237″[1]
Apparent magnitude (V) 7.66
Characteristics
Spectral type K6V[2]
U−B color index 1.12
B−V color index 1.18
V−R color index 0.71
Astrometry
Radial velocity (Rv)−9.78±0.12[1] km/s
Proper motion (μ) RA: 461.603 mas/yr[1]
Dec.: −471.880 mas/yr[1]
Parallax (π)88.6737 ± 0.0173 mas[1]
Distance36.782 ± 0.007 ly
(11.277 ± 0.002 pc)
Absolute magnitude (MV)7.39[3]
Details[2][4]
Mass0.69 M☉
Radius0.533 ± 0.04[note 1] R☉
Luminosity (bolometric)0.126 ± 0.008 L☉
Surface gravity (log g)4.604±0.017 cgs
Temperature4404±10 K
Metallicity([Si/H] dex) -0.02
Metallicity [Fe/H]-0.28 dex
Rotation47.13 ± 6.98
Rotational velocity (v sin i)2.194±0.118 km/s
Age5.61 ± 0.61 Gyr
Other designations
CD−42°5678, Gaia DR2 5412947081287925504, GJ 370, HD 85512, HIP 48331, LHS 2201, 2MASS J09510700-4330097[5]
Database references
SIMBADdata

Position

HD 85512 lies in Vela, 3′32″ west of and 10′54″ north of LZ Velorum (HD 86005), a chromospherically active giant, variable star, at 2090 light years away, of orange-to-red color and similarly average magnitude.[7]

Planetary system
Main article: HD 85512 b
Artists's impression of HD 85512 b.[8] Credit: ESO/M. Kornmesser.

On August 19, 2011, a ≥3.6 Earth-mass planet was discovered using HARPS that is "just inside" the habitable zone, along with the inner planets of e (or 82 G.) Eridani, and HD 192310 c in Capricornus. These two other systems are closer to Earth than this system.[9] Modelling at the time of the discovery announcement found that the planet could be cool enough to host liquid water if it has more than 50% cloud coverage,[10] but with revised models of the habitable zone two years later it was found to be too hot to be potentially habitable.[11] For a time it ranked fifth-best for habitability in the Planetary Habitability Laboratory's Habitable Exoplanets Catalog, which later listed it in an article about "false starts" in the search for potentially habitable exoplanets.[12]

In 2023, a study reassessed the radial velocity data of HD 85512. A signal was detected with a period of 51 days, inconsistent with the previously published 58-day orbital period of HD 85512 b, but consistent with previous estimates of the stellar rotation period. This indicates that the signal is very likely to be caused by the stellar rotation, rather than an orbiting planet.[6]: 25–27 [6]: 44 

The HD 85512 planetary system[9]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b (dubious) ≥3.6 M🜨 0.26 ± 0.005 58.43 ± 0.13 0.11 ± 0.1 — —

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. Anglada-Escudé, Guillem; Butler, R. Paul (2012), "The HARPS-TERRA project. I. Description of the algorithms, performance, and new measurements on a few remarkable stars observed by HARPS", The Astrophysical Journal Supplement Series, 200 (2): 15, arXiv:1202.2570, Bibcode:2012ApJS..200...15A, doi:10.1088/0067-0049/200/2/15, S2CID 118528839
  3. 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.
  4. Spectroscopic Parameters and atmosphEric ChemIstriEs of Stars (SPECIES) I. Code description and dwarf stars catalogue Full table D.1
  5. "HD 85512". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-09-22.
  6. Laliotis, Katherine; Burt, Jennifer A.; Mamajek, Eric E.; et al. (22 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". arXiv:2302.10310 [astro-ph.EP].
  7. "LZ Velorum - Universe Guide".
  8. "Fifty New Exoplanets Discovered by HARPS". ESO Science Release. 12 September 2011. Retrieved 13 September 2011.
  9. Pepe, F.; et al. (2011). "The HARPS search for Earth-like planets in the habitable zone. I. Very low-mass planets around HD 20794, HD 85512, and HD 192310". Astronomy and Astrophysics. 534. A58. arXiv:1108.3447. Bibcode:2011A&A...534A..58P. doi:10.1051/0004-6361/201117055.
  10. Kaltenegger, L.; Udry, S.; Pepe, F. (2011). "A Habitable Planet around HD 85512?". arXiv:1108.3561 [astro-ph.EP].
  11. Kopparapu, Ravi Kumar; et al. (2013). "Habitable Zones Around Main-Sequence Stars: New Estimates". The Astrophysical Journal. 765 (2): 131. arXiv:1301.6674. Bibcode:2013ApJ...765..131K. doi:10.1088/0004-637X/765/2/131. S2CID 76651902.
  12. "False Starts: Potentially Habitable Exoplanets - Planetary Habitability Laboratory @ UPR Arecibo". Archived from the original on 2021-10-18. Retrieved 2020-11-15.

Notes
  1. From , where is the radius, is the luminosity, is the effective surface temperature and is the Stefan–Boltzmann constant.
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