Astronomy:HD 154345

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Short description: Star in the constellation Hercules
HD 154345
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Location of HD 154345 (circled in red)
Observation data
Equinox J2000.0]] (ICRS)
Constellation Hercules[1]
Right ascension  17h 02m 36.40381s[2]
Declination +47° 04′ 54.7642″[2]
Apparent magnitude (V) +6.76[1]
Characteristics
Evolutionary stage main sequence[2]
Spectral type G8V[3]
U−B color index 0.27
B−V color index 0.728±0.005[1]
Astrometry
Radial velocity (Rv)−47.08±0.12[2] km/s
Proper motion (μ) RA: 123.274[2] mas/yr
Dec.: 853.639[2] mas/yr
Parallax (π)54.7359 ± 0.0176[2] mas
Distance59.59 ± 0.02 ly
(18.270 ± 0.006 pc)
Absolute magnitude (MV)+5.41[1]
Details[4]
Mass0.89±0.04[5] M☉
Radius0.85±0.01 R☉
Luminosity0.620±0.002 L☉
Surface gravity (log g)4.53±0.01 cgs
Temperature5,557±15 K
Metallicity [Fe/H]−0.14±0.04[6] dex
Rotation27.8±1.7 d[7]
Age4.10±1.20 Gyr
Other designations
BD+47°2420, GC 23011, GJ 651, HD 154345, HIP 83389, SAO 46452[8]
Database references
SIMBADdata
Exoplanet Archive154345 data

HD 154345 is a star in the northern constellation of Hercules. With an apparent visual magnitude of +6.76[1] it is a challenge to view with the naked eye, but using binoculars it is an easy target.[9] The distance to this star is 59.6 light years based on parallax, but it is drifting closer with a radial velocity of −47 km/s.[2] At least one exoplanet is orbiting this star.[10]

The stellar classification of HD 154345 is G8V,[3] matching an ordinary G-type main-sequence star that is generating energy by core hydrogen fusion. The magnetic activity cycle of this star is correlated with the radial velocity variations induced by its putative planetary companion.[11][12] It is around four[4] billion years old and is spinning with a rotation period of 28 days.[7] The star is smaller and less massive than the Sun. It is radiating 62% of the luminosity of the Sun from its photosphere at an effective temperature of 5,557 K.[4]

Planetary system

In 2006, a long-period, wide-orbiting planet was observed by radial velocity, and published in May 2007, gaining the designation HD 154345 b.[10] It has been called a "Jupiter twin".[13] While the existence of HD 154345 b has been unclear due to the correlation of its orbital period with the star's activity cycle,[11] a study in 2021 confirmed its planetary nature.[14]

The complete observation of its nine-year orbit rules out any interior planets of minimum mass (m sini) greater than 0.3 Jupiter.[13] The star rotates at an inclination of 50+40−26 degrees relative to Earth.[7] It is probable that the planet shares that inclination.[15][16] In 2023, the inclination and true mass of HD 154345 b were determined via astrometry, consistent within the margin of error with the stellar rotational inclination.[17] More precise measurements found a nearly edge-on inclination.[5]

The system's habitable zone stretches from 0.64 astronomical unit|AU out to 1.26 AU, and is narrower than the Sun's. It forms a stable region where an Earth-mass exoplanet could orbit.[18]

The HD 154345 planetary system[5]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(years) 		Eccentricity Inclination Radius
b 1.186+0.095
−0.059 MJ 		4.158+0.066
−0.067 		8.981+0.079
−0.076 		0.058±0.019 88±20° —

References

  1. ↑ 1.0 1.1 1.2 1.3 1.4 Anderson, E.; Francis, Ch. (2012). "XHIP: An extended hipparcos compilation". Astronomy Letters 38 (5): 331. doi:10.1134/S1063773712050015. Bibcode: 2012AstL...38..331A. 
  2. ↑ 2.0 2.1 2.2 2.3 2.4 2.5 2.6 Vallenari, A. et al. (2022). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy & Astrophysics. doi:10.1051/0004-6361/202243940  Gaia DR3 record for this source at VizieR.
  3. ↑ 3.0 3.1 Cowley, A. P. et al. (1967). "Spectral classification and photometry of high proper motion stars". The Astronomical Journal 72: 1334. doi:10.1086/110413. Bibcode: 1967AJ.....72.1334C. 
  4. ↑ 4.0 4.1 4.2 Bonfanti, A.; Ortolani, S.; Nascimbeni, V. (2016). "Age consistency between exoplanet hosts and field stars". Astronomy & Astrophysics 585: 14. doi:10.1051/0004-6361/201527297. A5. Bibcode: 2016A&A...585A...5B. 
  5. ↑ 5.0 5.1 5.2 Giovinazzi, Mark R. et al. (2025-07-01). "The NEID Earth Twin Survey. II. Dynamical Masses in Seven High-acceleration Star Systems". The Astronomical Journal 170 (1): 52. doi:10.3847/1538-3881/add922. ISSN 0004-6256. Bibcode: 2025AJ....170...52G. 
  6. ↑ Aguilera-Gómez, Claudia et al. (June 2018). "Lithium abundance patterns of late-F stars: an in-depth analysis of the lithium desert". Astronomy & Astrophysics 614: 15. doi:10.1051/0004-6361/201732209. A55. Bibcode: 2018A&A...614A..55A. 
  7. ↑ 7.0 7.1 7.2 Simpson, E. K. et al. (November 2010). "Rotation periods of exoplanet host stars". Monthly Notices of the Royal Astronomical Society 408 (3): 1666–1679. doi:10.1111/j.1365-2966.2010.17230.x. Bibcode: 2010MNRAS.408.1666S. 
  8. ↑ "HD 154345". SIMBAD. Centre de données astronomiques de Strasbourg. http://simbad.u-strasbg.fr/simbad/sim-basic?Ident=HD+154345. 
  9. ↑ "The astronomical magnitude scale". International Comet Quarterly. http://www.icq.eps.harvard.edu/MagScale.html. 
  10. ↑ 10.0 10.1 Wright, J. T. et al. (2007). "Four New Exoplanets and Hints of Additional Substellar Companions to Exoplanet Host Stars". The Astrophysical Journal 657 (1): 533–545. doi:10.1086/510553. Bibcode: 2007ApJ...657..533W. 
  11. ↑ 11.0 11.1 Wright, J. T. (October 2015). "Twenty Years of Precise Radial Velocities at Keck and Lick Observatories". in Boisse, I.; Demangeon, O.; Bouchy, F. et al.. Proceedings of colloquium 'Twenty years of giant exoplanets' held at Observatoire de Haute Provence, France, October 5-9, 2015. Observatoire de Haute-Provence, Institut Pythéas. pp. 8–17. Bibcode: 2015tyge.conf....8W. 
  12. ↑ Wright, Jason Thomas; Miller, Brendan (August 2015). "Magnetism and Activity of Planet-Hosting Stars". IAU General Assembly, Meeting #29. 2258453. Bibcode: 2015IAUGA..2258453W. 
  13. ↑ 13.0 13.1 Wright, J. T. et al. (2008). "The Jupiter Twin HD 154345b". The Astrophysical Journal Letters 683 (1): L63–L66. doi:10.1086/587461. Bibcode: 2008ApJ...683L..63W. 
  14. ↑ Rosenthal, Lee J.; Fulton, Benjamin J.; Hirsch, Lea A.; Isaacson, Howard T.; Howard, Andrew W.; Dedrick, Cayla M.; Sherstyuk, Ilya A.; Blunt, Sarah C. et al. (2021). "The California Legacy Survey. I. A Catalog of 178 Planets from Precision Radial Velocity Monitoring of 719 Nearby Stars over Three Decades". The Astrophysical Journal Supplement Series 255 (1): 8. doi:10.3847/1538-4365/abe23c. Bibcode: 2021ApJS..255....8R. 
  15. ↑ "hd_154345_b". Extrasolar Planets Encyclopaedia. 1995. https://exoplanet.eu/catalog/hd_154345_b--338/. Retrieved November 12, 2012. 
  16. ↑ Sanchis-Ojeda, Roberto; Winn, Josh N.; Fabrycky, Daniel C. (2012). "Starspots and spin-orbit alignment for Kepler cool host stars". Astronomische Nachrichten 334 (1–2): 180–183. doi:10.1002/asna.201211765. Bibcode: 2013AN....334..180S. 
  17. ↑ Xiao, Guang-Yao et al. (March 2023). "The Masses of a Sample of Radial-Velocity Exoplanets with Astrometric Measurements". Research in Astronomy and Astrophysics 23 (5). doi:10.1088/1674-4527/accb7e. Bibcode: 2023RAA....23e5022X. 
  18. ↑ Funk, B.; Libert, A. -S.; Süli, Á.; Pilat-Lohinger, E. (February 2011). "On the influence of the Kozai mechanism in habitable zones of extrasolar planetary systems". Astronomy and Astrophysics 526: 7. doi:10.1051/0004-6361/201015218. A98. Bibcode: 2011A&A...526A..98F. 

Coordinates: Sky map 17h 02m 36.40s, +47° 04′ 54.77″



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