HR 7722

HR 7722
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]
Characteristics
Spectral type K2+ V[3]
U−B color index 0.64[2]
B−V color index 0.88[2]
Variable type Suspected
Astrometry
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
Distance 29.06 ± 0.08 ly
(8.91 ± 0.02 pc)
Absolute magnitude (MV) 6.0[5]
Details
Mass 0.78 ± 0.04[6] M☉
Radius 0.79–0.85[7] R☉
Surface gravity (log g) 4.38 ± 0.19[8]
Luminosity 0.385 ± 0.007[9] L☉
Temperature 5069 ± 49[8] K
Metallicity [Fe/H] -0.01 ± 0.05[8] dex
Rotation 47.7 ± 4.9 days[9]
Rotational velocity (v sin i) <3[9] km/s
Age 7.5–8.9[5] Gyr
Other designations
5 G. Capricorni, Gl 785, CD -27°14659, HD 192310, LHS 488, LTT 8009, GCTP 4804.00, SAO 189065, FK5 , NSV 12933, HIP 99825.
Database references
SIMBAD data
ARICNS data

HR 7722 (also known as 5 G. Capricorni or Gliese 785) is a star in the constellation 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. HR 7722 is suspected of being a variable star, but this is unconfirmed.

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] 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.[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.[10]

Planetary system

The system has a Neptune-mass planet "b", discovered in 2010.[11] A second planet "c" was found in this system in 2011 by the HARPS GTO program. 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.[9][12]

The HR 7722 system
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity
b 0.053 ± 0.0028 MJ 0.32 ± 0.005 74.72 0.13 ± 0.04
c 0.075 ± 0.016 MJ 1.18 525.8 ± 9.2 0.32 ± 0.11

References

  1. ^ a b c d e van Leeuwen, F. (November 2007), "Validation of the new Hipparcos reduction", Astronomy and Astrophysics 474 (2): 653–664, 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. ^ 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, 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, 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, Bibcode 2001A&A...367..521P, doi:10.1051/0004-6361:20000451 
  8. ^ 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 
  9. ^ a b c d 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..35349058P, doi:10.1051/0004-6361/201117055 
  10. ^ 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 
  11. ^ Schneider, Jean, "Gl 785", Extrasolar Planets Encyclopaedia, http://exoplanet.eu/star.php?st=Gl%20785, retrieved 2011-10-29 
  12. ^ Schneider, Jean, "HD 192310 c", Extrasolar Planets Encyclopaedia, http://exoplanet.eu/planet.php?p1=HD+192310&p2=c, retrieved 2011-10-29 

External links

Stars of Capricornus
Flamsteed