HD 192310

HD 192310 (also known as 5 G. Capricorni or Gliese 785) is a star in the southern constellation of Capricornus. It is located in the solar neighborhood at a distance of 28.7 light-years (8.8 parsecs), and is within the range of luminosity needed to be viewed from the Earth with the unaided eye. (According to the Bortle scale, it can be viewed from dark suburban skies.) HD 192310 is suspected of being a variable star, but this is unconfirmed.

HD 192310
Location of HD 192310 (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Capricornus
Right ascension 20h 15m 17.39138s[1]
Declination −27° 01′ 58.7116″[1]
Apparent magnitude (V) 5.73[2]
Characteristics
Spectral type K2+ V[3]
U−B color index 0.64[2]
B−V color index 0.88[2]
Variable type Suspected[4]
Astrometry
Radial velocity (Rv)−54.41±0.13[1] km/s
Proper motion (μ) RA: 1242.763 mas/yr[1]
Dec.: −181.175 mas/yr[1]
Parallax (π)113.4872 ± 0.0516 mas[1]
Distance28.74 ± 0.01 ly
(8.812 ± 0.004 pc)
Absolute magnitude (MV)6.0[5]
Details
Mass0.78 ± 0.04[6] M☉
Radius0.79–0.85[7] R☉
Luminosity0.385 ± 0.007[8] L☉
Surface gravity (log g)4.38 ± 0.19[9] cgs
Temperature5069 ± 49[9] K
Metallicity [Fe/H]-0.01 ± 0.05[9] dex
Rotation47.7 ± 4.9 days[8]
Rotational velocity (v sin i)<3[8] km/s
Age7.5–8.9[5] Gyr
Other designations
5 G. Capricorni, CD-27°14659, GCTP 4804.00, Gl 785, HD 192310, HIP 99825, HR 7722, LHS 488, LTT 8009, NSV 12933, SAO 189065
Database references
SIMBADdata
ARICNSdata

Description

This is a K-type main sequence star with a stellar classification of K2+ V.[3] HD 192310 has about 78% of the Sun's mass[6] and, depending on the estimation method, 79% to 85% of the radius of the Sun.[7] The effective temperature of the photosphere is about 5069 K, giving it the orange-hued glow of a K-type star.[10] It is older than the Sun, with age estimates in the range 7.5–8.9 billion years.[5] The proportion of elements other than hydrogen and helium, known as the metallicity, is similar to that of the Sun.[9] It is spinning slowly, completing a rotation roughly every 48 days.[8]

The space velocity components of this star are (U, V, W) = (–69, –13, –14) km/s. It is following an orbit through the Milky Way galaxy that has an orbital eccentricity of 0.18 at a mean galactocentric distance of 8.1 kpc.[11] The star will achieve perihelion in around 82,200 years when it comes within 20.18 ly (6.188 pc) of the Sun.[12]

Planetary system

The system has a Neptune-mass planet "b", discovered in 2010.[13] A second planet "c" was found in this system in 2011 by the HARPS GTO program, along with the now-doubtful HD 85512 b and the planets of 82 G. Eridani. The uncertainty in the mass of the second planet was much higher than for the first because of the lack of coverage around the full orbit. Both planets may be similar in composition to Neptune. They are orbiting along the inner and outer edges of the habitable zone for this star.[8][14]

A study in 2023 updated the parameters of these two planets, and identified a number of additional radial velocity signals. While most of these signals were attributed to stellar activity, one was considered a planet candidate. If real, this third planet would be a super-Earth orbiting closer to the star than the two known planets.[15]: 31  However, another 2023 study did not find this candidate signal and also attributed it to stellar activity.[16]: 10 

The HD 192310 planetary system[16]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b ≥16.1±0.7 M🜨 0.32±0.01 74.25±0.04 0.11±0.02 — —
c ≥15.9±0.9 M🜨 1.21±0.02 534.9+5.9
−5.1		 0.06+0.05
−0.04		 — —

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, S2CID 119476992
  4. Samus, N. N.; Durlevich, O. V.; et al. (2009), "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)", VizieR On-line Data Catalog: B/GCVS. Originally Published in: 2009yCat....102025S, 1: B/gcvs, Bibcode:2009yCat....102025S
  5. Mamajek, Eric E.; Hillenbrand, Lynne A. (November 2008), "Improved Age Estimation for Solar-Type Dwarfs Using Activity-Rotation Diagnostics", The Astrophysical Journal, 687 (2): 1264–1293, arXiv:0807.1686, Bibcode:2008ApJ...687.1264M, doi:10.1086/591785, S2CID 27151456
  6. Santos, N. C.; Israelian, G.; Mayor, M. (July 2001), "The metal-rich nature of stars with planets", Astronomy and Astrophysics, 373 (3): 1019–1031, arXiv:astro-ph/0105216, Bibcode:2001A&A...373.1019S, doi:10.1051/0004-6361:20010648, S2CID 119347084
  7. Pasinetti Fracassini, L. E.; et al. (February 2001), "Catalogue of Apparent Diameters and Absolute Radii of Stars (CADARS) - Third edition - Comments and statistics", Astronomy and Astrophysics, 367 (2): 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451, S2CID 425754
  8. Pepe, F.; et al. (2011), "The HARPS search for Earth-like planets in the habitable zone", VizieR On-line Data Catalog: J/A+A/534/A58, vol. 534, pp. A58, arXiv:1108.3447, Bibcode:2011yCat..35340058P, doi:10.1051/0004-6361/201117055, S2CID 15088852
  9. Ecuvillon, A.; et al. (May 2004), "Nitrogen abundances in planet-harbouring stars", Astronomy and Astrophysics, 418 (2): 703–715, arXiv:astro-ph/0401396, Bibcode:2004A&A...418..703E, doi:10.1051/0004-6361:20035717, S2CID 55400558
  10. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on March 18, 2012, retrieved 2012-01-16
  11. Porto de Mello, Gustavo; del Peloso, Eduardo F. (April 2006), "Astrobiologically Interesting Stars Within 10 Parsecs of the Sun", Astrobiology, 6 (2): 308–331, arXiv:astro-ph/0511180, Bibcode:2006AsBio...6..308P, doi:10.1089/ast.2006.6.308, PMID 16689649, S2CID 119459291
  12. Bailer-Jones, C. A. L. (March 2015), "Close encounters of the stellar kind", Astronomy & Astrophysics, 575: 13, arXiv:1412.3648, Bibcode:2015A&A...575A..35B, doi:10.1051/0004-6361/201425221, S2CID 59039482, A35
  13. Howard, Andrew W.; Johnson, John Asher; et al. (March 2011). "The NASA-UC Eta-Earth Program: III. A Super-Earth orbiting HD 97658 and a Neptune-mass planet orbiting Gl 785". The Astrophysical Journal. 730 (1): 10. arXiv:1011.0414. Bibcode:2011ApJ...730...10H. doi:10.1088/0004-637X/730/1/10. S2CID 17943021.
  14. Schneider, Jean, "HD 192310 c", Extrasolar Planets Encyclopaedia, archived from the original on 2011-11-08, retrieved 2011-10-29
  15. Laliotis, Katherine; Burt, Jennifer A.; et al. (April 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. 165 (4): 176. arXiv:2302.10310. Bibcode:2023AJ....165..176L. doi:10.3847/1538-3881/acc067.
  16. Cretignier, M.; Dumusque, X.; et al. (August 2023). "YARARA V2: Reaching sub m/s precision over a decade using PCA on line-by-line RVs". arXiv:2308.11812 [astro-ph.EP].
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