HD 159868

HD 159868 is a star in the southern constellation of Scorpius, positioned about 0.3° to the ESE of the bright star Theta Scorpii.[9] With an apparent visual magnitude of +7.24,[3] it is too faint to be visible to the naked eye but can be viewed with a small telescope. The star lies at a distance of 183 light years from the Sun based on parallax, but is drifting closer with a radial velocity of −24 km/s.[3]

HD 159868
Observation data
Epoch J2000      Equinox J2000
Constellation Scorpius[1]
Right ascension 17h 38m 59.5264s[2]
Declination −43° 08′ 43.8443″[2]
Apparent magnitude (V) +7.24[3]
Characteristics
Spectral type G5V[4]
Apparent magnitude (J) 5.941±0.021[5]
Apparent magnitude (H) 5.567±0.026[5]
Apparent magnitude (K) 5.535±0.024[5]
B−V color index 0.714±0.012[3]
Astrometry
Radial velocity (Rv)−23.80±0.76[3] km/s
Proper motion (μ) RA: −230.510[2] mas/yr
Dec.: −167.766[2] mas/yr
Parallax (π)17.8763 ± 0.0530[2] mas
Distance182.5 ± 0.5 ly
(55.9 ± 0.2 pc)
Absolute magnitude (MV)+3.63[6]
Details[6]
Mass1.087+0.032
−0.033 M☉[6]
1.123±0.018[7] M☉
Radius1.97±0.04 R☉[7]
2.03+0.05
−0.04[2] R☉
Luminosity3.59±0.02[2] L☉
Surface gravity (log g)3.96±0.02 cgs
Temperature5,558±15 K
Metallicity [Fe/H]−0.08±0.01 dex
Rotational velocity (v sin i)2.1 km/s
Age6.6±0.2[7] Gyr
Other designations
CD−43°11901, GJ 4014, HD 159868, HIP 86375, SAO 228234[8]
Database references
SIMBADdata

The spectrum of this object matches a G-type main-sequence star with a stellar classification of G5V. It has a relatively low surface gravity for its class, which suggests it is slightly evolved off the main sequence. The star is chromospherically inactive with a slow rotation rate, having a projected rotational velocity of 2.1 km/s.[6] It is an estimated 6.6[7] billion years old with 8–12% more mass than the Sun and nearly double the Sun's radius. The star is radiating 3.6 times the luminosity of the Sun from its photosphere at an effective temperature of 5,558 K.[2]

Planetary system

In 2007, a planet of the star was announced by astronomer Simon J. O'Toole and collaborators.[10] The planet (designated HD 159868 b) is likely to be a gas giant. Preliminary orbital elements suggested the orbit is extremely eccentric at the average distance of 2 astronomical units (AU), ranging as close as 0.62 AU to as far as 3.38 AU. In 2012, a second planet of the star was announced by astronomer Robert A. Wittenmyer and associates. The orbit of the first planet was significantly revised during the investigation.[6]

The HD 159868 planetary system[10][6]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
c ≥0.73±0.05 MJ 1.00±0.01 352.3±1.3 0.15±0.05 — —
b ≥2.1±0.1 MJ 2.25±0.03 1,178.4±8.8 0.01±0.03 — —

See also

References
  1. Roman, Nancy G. (1987). "Identification of a Constellation From a Position". Publications of the Astronomical Society of the Pacific. 99 (617): 695–699. Bibcode:1987PASP...99..695R. doi:10.1086/132034. Vizier query form
  2. Brown, A. G. A.; et al. (Gaia collaboration) (August 2018). "Gaia Data Release 2: Summary of the contents and survey properties". Astronomy & Astrophysics. 616. A1. arXiv:1804.09365. Bibcode:2018A&A...616A...1G. doi:10.1051/0004-6361/201833051. Gaia DR2 record for this source at VizieR.
  3. Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters. 38 (5): 331. arXiv:1108.4971. Bibcode:2012AstL...38..331A. doi:10.1134/S1063773712050015. S2CID 119257644.
  4. Houk, N. (1978). "Michigan catalogue of two-dimensional spectral types for the HD stars". 2. Dept. of Astronomy, University of Michigan. Bibcode:1978mcts.book.....H. Cite journal requires |journal= (help)
  5. Skrutskie, M. F.; et al. (2006). "The Two Micron All Sky Survey (2MASS)". The Astronomical Journal. 131 (2): 1163–1183. Bibcode:2006AJ....131.1163S. doi:10.1086/498708. Vizier catalog entry
  6. Wittenmyer, Robert A.; et al. (2012). "The Anglo-Australian Planet Search. XXII. Two New Multi-planet Systems". The Astrophysical Journal. 753 (2): 169. arXiv:1205.2765. Bibcode:2012ApJ...753..169W. doi:10.1088/0004-637X/753/2/169.
  7. Delgado Mena, E.; et al. (April 2019). "Abundance to age ratios in the HARPS-GTO sample with Gaia DR2. Chemical clocks for a range of [Fe/H]". Astronomy & Astrophysics. 624: 24. arXiv:1902.02127. Bibcode:2019A&A...624A..78D. doi:10.1051/0004-6361/201834783. A78.
  8. "HD 159868". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2019-09-10.
  9. Sinnott, Roger W.; Perryman, Michael A. C. (1997). Millennium Star Atlas. 3. Sky Publishing Corporation and the European Space Agency. p. 1460. ISBN 0-933346-84-0.
  10. O'Toole, Simon J.; et al. (2007). "New Planets around Three G Dwarfs". The Astrophysical Journal. 660 (2): 1636–1641. arXiv:astro-ph/0702213. Bibcode:2007ApJ...660.1636O. doi:10.1086/513563.

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