Astronomy:HD 6718
| Observation data Equinox J2000.0]] (ICRS) | |
|---|---|
| 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[1] mas |
| Distance | 167.7 ± 0.5 ly (51.4 ± 0.1 pc) |
| Absolute magnitude (MV) | 4.754[6] |
| Details | |
| Mass | 0.98±0.04[7] M☉ |
| Radius | 1.01±0.02[7] R☉ |
| Luminosity | 1.07±0.01[7] L☉ |
| Surface gravity (log g) | 4.42±0.02[8] cgs |
| Temperature | 5,728±5[8] K |
| Metallicity [Fe/H] | −0.064±0.004[8] dex |
| Rotational velocity (v sin i) | 2.00±0.12[8] km/s |
| Age | 6.0±2.4[7] Gyr |
| Other designations | |
| Database references | |
| SIMBAD | data |
| Exoplanet Archive | data |
| Extrasolar Planets Encyclopaedia | data |
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 |♃|J}}}}}} 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 |♃|J}}}}}}. This makes it a brown dwarf.[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° |
— |
See also
- List of extrasolar planets
References
- ↑ 1.0 1.1 1.2 1.3 1.4 Brown, A. G. A. (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics 616: A1. doi:10.1051/0004-6361/201833051. Bibcode: 2018A&A...616A...1G. Gaia DR2 record for this source at VizieR.
- ↑ 2.0 2.1 2.2 2.3 2.4 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A.
- ↑ 3.0 3.1 Houk, N.; Swift, C. (1999). "Michigan catalogue of two-dimensional spectral types for the HD Stars". Michigan Spectral Survey 5. Bibcode: 1999MSS...C05....0H.
- ↑ Høg, E. et al. (2000). The Tycho-2 catalogue of the 2.5 million brightest stars. 355. L27. doi:10.1888/0333750888/2862. ISBN 978-0333750889. Bibcode: 2000A&A...355L..27H.
- ↑ 5.0 5.1 5.2 Cutri, R. M.; Skrutskie, M. F.; Van Dyk, S.; Beichman, C. A. et al. (June 2003). "2MASS All Sky Catalog of point sources". The IRSA 2MASS All-Sky Point Source Catalog, NASA/IPAC Infrared Science Archive.. Bibcode: 2003tmc..book.....C.
- ↑ 6.0 6.1 6.2 6.3 Naef, Dominique; Mayor, Michel; Lo Curto, Gaspare; Bouchy, François; Lovis, Christophe; Moutou, Claire; Benz, Willy; Pepe, Francesco et al. (2010). "The HARPS Search for Southern Extrasolar Planets XXIII. 8 Planetary Companions to Low-activity Solar-type Stars". Astronomy and Astrophysics 523: A15. doi:10.1051/0004-6361/200913616. Bibcode: 2010A&A...523A..15N. http://www.aanda.org/articles/aa/full_html/2010/15/aa13616-09/aa13616-09.html.
- ↑ 7.0 7.1 7.2 7.3 7.4 Bonfanti, A. et al. (2015). "Revising the ages of planet-hosting stars". Astronomy and Astrophysics 575: A18. doi:10.1051/0004-6361/201424951. Bibcode: 2015A&A...575A..18B. http://www.aanda.org/articles/aa/full_html/2015/03/aa24951-14/aa24951-14.html.
- ↑ 8.0 8.1 8.2 8.3 8.4 8.5 8.6 dos Santos, Leonardo A. et al. (August 2016), "The Solar Twin Planet Search. IV. The Sun as a typical rotator and evidence for a new rotational braking law for Sun-like stars", Astronomy & Astrophysics 592: 8, doi:10.1051/0004-6361/201628558, A156, Bibcode: 2016A&A...592A.156D.
- ↑ "HD 6718". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+6718.
- ↑ Ramírez, I. et al. (December 2014). "The Solar Twin Planet Search. I. Fundamental parameters of the stellar sample". Astronomy & Astrophysics 572: 19. doi:10.1051/0004-6361/201424244. A48. Bibcode: 2014A&A...572A..48R.
- ↑ 11.0 11.1 Kiefer, F. et al. (January 2021). "Determining the true mass of radial-velocity exoplanets with Gaia. Nine planet candidates in the brown dwarf or stellar regime and 27 confirmed planets". Astronomy & Astrophysics 645. doi:10.1051/0004-6361/202039168. Bibcode: 2021A&A...645A...7K.
Coordinates: 
01h 07m 48.6625s, −08° 14′ 01.341″
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