HD 6718

HD 6718
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Cetus
Right ascension 01h 07m 48.6630s[1]
Declination –08° 14′ 01.3306″[1]
Apparent magnitude (V) 8.45[2]
Characteristics
Evolutionary stage main sequence
Spectral type G5V[3]
Apparent magnitude (B) 9.087[4]
Apparent magnitude (J) 7.269[5]
Apparent magnitude (H) 6.99[5]
Apparent magnitude (K) 6.876[5]
B−V color index 0.662±0.009[2]
Astrometry
Radial velocity (Rv)+34.76[2] km/s
Proper motion (μ) RA: 192.637±0.114[1] mas/yr
Dec.: 20.080±0.069[1] mas/yr
Parallax (π)19.4476 ± 0.0523 mas[1]
Distance167.7 ± 0.5 ly
(51.4 ± 0.1 pc)
Absolute magnitude (MV)4.754[6]
Details
Mass0.98±0.04[7] M☉
Radius1.01±0.02[7] R☉
Luminosity1.07±0.01[7] L☉
Surface gravity (log g)4.42±0.02[8] cgs
Temperature5,728±5[8] K
Metallicity [Fe/H]−0.064±0.004[8] dex
Rotational velocity (v sin i)2.00±0.12[8] km/s
Age6.0±2.4[7] Gyr
Other designations
BD–09°221, HD 6718, HIP 5301, SAO 129137, PPM 183064, LTT 641, NLTT 3753[9]
Database references
SIMBADdata
Exoplanet Archivedata

HD 6718 is a solar twin[10] star in the equatorial constellation of Cetus. It has a yellow hue but is too faint to be viewed with the naked eye, having an apparent visual magnitude of 8.45.[2] The distance to this object, as determined from parallax measurements, is 168 light years. It is drifting away from the Sun with a radial velocity of +35 km/s.[2]

This object is an ordinary G-type main-sequence star with a stellar classification of G5V,[3] with the luminosity class of 'V' indicating it is generating energy through hydrogen fusion at its core. It is around six billion years old with a leisurely rotation rate, having a projected rotational velocity of 2 km/s.[8] The level of magnetic activity in the chromosphere is considered very low[6] and it has a near solar metallicity.[8] Being a solar twin, has nearly the same mass and radius as the Sun. The star is radiating 1.07[7] times the luminosity of the Sun from its photosphere at an effective temperature of 5,728 K.[8]

In 2009, a substellar companion (HD 6718 b) with a minimum mass of 1.56 MJ was found in orbit around the star with a period of 6.83 years.[6] In 2020, the inclination of this object was measured, revealing its true mass to be 62.8 MJ. This makes it a brown dwarf.[11]

The HD 6718 planetary system[6][11]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
b 62.79+16.98
−13.80 MJ 		3.56+0.24
−0.15 		2496±176 0.10+0.11
−0.04 		1.488+0.410
−0.310° 		—
  1. ^ a b c d e Cite error: The named reference Gaia DR2 was invoked but never defined (see the help page).
  2. ^ a b c d e Cite error: The named reference Anderson2012 was invoked but never defined (see the help page).
  3. ^ a b Cite error: The named reference Houk1999 was invoked but never defined (see the help page).
  4. ^ Cite error: The named reference Høg2000 was invoked but never defined (see the help page).
  5. ^ a b c Cite error: The named reference Cutri2003 was invoked but never defined (see the help page).
  6. ^ a b c d Cite error: The named reference Naef2010 was invoked but never defined (see the help page).
  7. ^ a b c d e Cite error: The named reference Bonfanti2015 was invoked but never defined (see the help page).
  8. ^ a b c d e f g Cite error: The named reference dosSantos2016 was invoked but never defined (see the help page).
  9. ^ Cite error: The named reference SIMBAD was invoked but never defined (see the help page).
  10. ^ Cite error: The named reference Ramírez2014 was invoked but never defined (see the help page).
  11. ^ a b Cite error: The named reference Kiefer2020 was invoked but never defined (see the help page).