HD 192310

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HR 7722
Diagram showing star positions and boundaries of the Capricornus constellation and its surroundings
Cercle rouge 100%.svg
A star chart of the constellation of Capricornus showing the position of HR 7722 (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Capricornus
Right ascension  20h 15m 17.39122s[1]
Declination −27° 01′ 58.7121″[1]
Apparent magnitude (V) 5.73[2]
Spectral type K2+ V[3]
U−B color index 0.64[2]
B−V color index 0.88[2]
Variable type Suspected
Radial velocity (Rv)-54.2[4] km/s
Proper motion (μ) RA: 1241.85[1] mas/yr
Dec.: -180.96[1] mas/yr
Parallax (π)112.22 ± 0.30[1] mas
Distance29.06 ± 0.08 ly
(8.91 ± 0.02 pc)
Absolute magnitude (MV)6.0[5]
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, LHS 488, LTT 8009, NSV 12933, SAO 189065.
Database references

HR 7722 (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 just over 29 light years, 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.) HR 7722 is suspected of being a variable star, but this is unconfirmed.

This is a K-type main sequence star with a stellar classification of K2+ V.[3] HR 7722 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[edit]

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 HD 85512 b and the planets of 82 G. Eridani. The uncertainty in the mass of the second planet is 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]

The HD 192310 planetary system
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b ≥16.9 ± 0.9 M 0.32 ± 0.005 74.72 0.13 ± 0.04
c ≥24 ± 5 M 1.18 ± 0.025 525.8 ± 9.2 0.32 ± 0.11

See also[edit]


  1. ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics, 474 (2): 653–664, arXiv:0708.1752, Bibcode:2007A&A...474..653V, doi:10.1051/0004-6361:20078357
  2. ^ a b c 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. ^ a b 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. ^ Nordström, B.; et al. (May 2004), "The Geneva-Copenhagen survey of the Solar neighbourhood. Ages, metallicities, and kinematic properties of ˜14 000 F and G dwarfs", Astronomy and Astrophysics, 418: 989–1019, arXiv:astro-ph/0405198, Bibcode:2004A&A...418..989N, doi:10.1051/0004-6361:20035959
  5. ^ a b c 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
  6. ^ a b 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
  7. ^ a b 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: 521–524, arXiv:astro-ph/0012289, Bibcode:2001A&A...367..521P, doi:10.1051/0004-6361:20000451
  8. ^ a b c d e Pepe, F.; et al. (2011), "The HARPS search for Earth-like planets in the habitable zone: I – Very low-mass planets around HD20794, HD85512 and HD192310", VizieR On-line Data Catalog: J/A+A/534/A58, arXiv:1108.3447, Bibcode:2011yCat..35340058P
  9. ^ a b c d 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
  10. ^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, 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
  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, A35.
  13. ^ Schneider, Jean, "Gl 785", Extrasolar Planets Encyclopaedia, retrieved 2011-10-29
  14. ^ Schneider, Jean, "HD 192310 c", Extrasolar Planets Encyclopaedia, archived from the original on 2011-11-08, retrieved 2011-10-29

External links[edit]