HD 168009

HD 168009 is a star in the northern constellation of Lyra. It has an apparent visual magnitude of 6.3,[2] placing it just above to below the normal limit of stars visible to the naked eye under good viewing conditions of 6-6.5. An annual parallax shift of 42.93 mas provides a distance estimate of 76 light years. It is moving closer to the Sun with a heliocentric radial velocity of −65 km/s.[4] In about 328,000 years from now, the star will make its closest approach at a distance of around 17 ly (5.1 pc).[10]

HD 168009
Observation data
Epoch J2000      Equinox J2000
Constellation Lyra
Right ascension 18h 15m 32.463s[1]
Declination +45° 12′ 33.54″[1]
Apparent magnitude (V) 6.307[2]
Characteristics
Spectral type G1 V[3]
U−B color index 0.115[2]
B−V color index 0.635[2]
Astrometry
Radial velocity (Rv)−64.9±0.1[4] km/s
Proper motion (μ) RA: −77.290±0.018 mas/yr[1]
Dec.: −114.748±0.019 mas/yr[1]
Parallax (π)42.9348 ± 0.0158 mas[1]
Distance75.97 ± 0.03 ly
(23.291 ± 0.009 pc)
Absolute magnitude (MV)4.52[2][5]
Absolute bolometric
magnitude (Mbol)		4.39±0.06[6]
Details[4]
Mass0.99 M☉
Radius1.14±0.04[6] R☉
Luminosity1.43[7] L☉
Surface gravity (log g)4.31 cgs
Temperature5,792±80 K
Metallicity [Fe/H]−0.02 dex
Rotation5.985±0.019 d[8]
Rotational velocity (v sin i)3[5] km/s
Age8.1 Gyr
Other designations
BD+45° 2684, GJ 9622, HD 168009, HIP 89474, HR 6847, SAO 47343, 2MASS J18153245+4512333[9]
Database references
SIMBADdata

This is a solar analog,[2] which means its measured properties are similar to those of the Sun. However, it is much older than the Sun with an estimated age of around 8.1 billion years.[4] The spectrum matches a stellar classification of G1 V,[3] indicating this is an ordinary G-type main-sequence star that is generating energy through hydrogen fusion at its core. The level of chromospheric activity is low, making it a candidate for a Maunder minimum event.[4]

HD 168009 has about the same mass as the Sun, but is 14% larger in radius.[6] It has a similar metallicity to the Sun – what astronomers term the abundance of elements other than hydrogen and helium – and is spinning with a rotation period of six days.[8] The star is radiating 1.43[7] times the Sun's luminosity from its photosphere at an effective temperature of 5,792 K.[4] It has been examined for an infrared excess that may indicate the presence of a circumstellar disk of dust, but no statistically significant excess was detected.[11][12]

Planetary system

In 2020, a candidate exoplanet was detected orbiting this star. With a minimum mass of 0.03 MJ (9.5 M🜨) and an orbital period of 15 days, this would most likely be a hot mini-Neptune.[13] The planet existence was confirmed in 2021.[14]

The HD 168009 planetary system[13][14]
Companion
(in order from star)		 Mass Semimajor axis
(AU)		 Orbital period
(days)		 Eccentricity Inclination Radius
b ≥0.0300+0.0038
−0.0037 MJ		 0.1192+0.0017
−0.0018		 15.1479+0.0035
−0.0037		 0.121+0.110
−0.082		 — —

References
  1. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
  2. Soubiran, C.; Triaud, A. (May 2004), "The Top Ten solar analogs in the ELODIE library", Astronomy and Astrophysics, 418 (3): 1089−1100, arXiv:astro-ph/0402094, Bibcode:2004A&A...418.1089S, doi:10.1051/0004-6361:20035708.
  3. Mahdi, D.; et al. (March 2016), "Solar twins in the ELODIE archive", Astronomy & Astrophysics, 587: 9, arXiv:1601.01599, Bibcode:2016A&A...587A.131M, doi:10.1051/0004-6361/201527472, S2CID 119205608, A131.
  4. Lubin, Dan; et al. (March 2012), "Frequency of Maunder Minimum Events in Solar-type Stars Inferred from Activity and Metallicity Observations", The Astrophysical Journal Letters, 747 (2): 6, Bibcode:2012ApJ...747L..32L, doi:10.1088/2041-8205/747/2/L32, L32.
  5. Takeda, Yoichi; et al. (February 2005), "High-Dispersion Spectra Collection of Nearby F--K Stars at Okayama Astrophysical Observatory: A Basis for Spectroscopic Abundance Standards", Publications of the Astronomical Society of Japan, 57 (1): 13–25, Bibcode:2005PASJ...57...13T, doi:10.1093/pasj/57.1.13.
  6. Fuhrmann, Klaus (July 2011), "Nearby stars of the Galactic disc and halo - V", Monthly Notices of the Royal Astronomical Society, 414 (4): 2893−2922, Bibcode:2011MNRAS.414.2893F, doi:10.1111/j.1365-2966.2011.18476.x.
  7. McDonald, I.; et al. (2012), "Fundamental parameters and infrared excesses of Hipparcos stars", Monthly Notices of the Royal Astronomical Society, 427 (1): 343–357, arXiv:1208.2037, Bibcode:2012MNRAS.427..343M, doi:10.1111/j.1365-2966.2012.21873.x, S2CID 118665352.
  8. Hempelmann, A.; et al. (February 2016), "Measuring rotation periods of solar-like stars using TIGRE. A study of periodic CaII H+K S-index variability", Astronomy & Astrophysics, 586: 19, Bibcode:2016A&A...586A..14H, doi:10.1051/0004-6361/201526972, A14.
  9. "HD 168009". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2018-01-18.
  10. Bailer-Jones, C. A. L. (March 2015), "Close encounters of the stellar kind", Astronomy & Astrophysics, 575: 13, arXiv:1412.3648, Bibcode:2015A&A...575A..35B, doi:10.1051/0004-6361/201425221, S2CID 59039482, A35.
  11. Sierchio, J. M.; et al. (April 2014), "The Decay of Debris Disks around Solar-type Stars", The Astrophysical Journal, 785 (1): 13, arXiv:1402.6308, Bibcode:2014ApJ...785...33S, doi:10.1088/0004-637X/785/1/33, S2CID 54077869, 33.
  12. Ballering, Nicholas P.; et al. (September 2013), "A Trend between Cold Debris Disk Temperature and Stellar Type: Implications for the Formation and Evolution of Wide-orbit Planets", The Astrophysical Journal, 775 (1): 14, arXiv:1308.2223, Bibcode:2013ApJ...775...55B, doi:10.1088/0004-637X/775/1/55, S2CID 119113700, 55.
  13. Hirsch, Lea A.; et al. (December 2020), "Understanding the Impacts of Stellar Companions on Planet Formation and Evolution: A Survey of Stellar and Planetary Companions within 25 pc", The Astronomical Journal, 161 (3): 134, arXiv:2012.09190, Bibcode:2021AJ....161..134H, doi:10.3847/1538-3881/abd639, S2CID 229297873.
  14. Rosenthal, Lee J.; 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, arXiv:2105.11583, Bibcode:2021ApJS..255....8R, doi:10.3847/1538-4365/abe23c, S2CID 235186973
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