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HD 164922

Coordinates: Sky map 18h 02m 30.86s, +26° 18′ 46.81″
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HD 164922

Position of star HD 164922 in the constellation Hercules
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Hercules
Right ascension 18h 02m 30.86s[1]
Declination +26° 18′ 46.81″[1]
Apparent magnitude (V) +7.01
Characteristics
Spectral type G9V[2]
U−B color index 0.47
B−V color index 0.80
V−R color index 0.42
R−I color index 0.36
Variable type suspected
Astrometry
Radial velocity (Rv)+22.8 km/s
Proper motion (μ) RA: 389.41 ± 0.36[1] mas/yr
Dec.: –602.03 ± 0.52[1] mas/yr
Parallax (π)45.21 ± 0.54 mas[1]
Distance72.1 ± 0.9 ly
(22.1 ± 0.3 pc)
Absolute magnitude (MV)5.31
Details
Mass0.874 ± 0.012[2] M☉
Radius0.999 ± 0.017[2] R☉
Luminosity0.703 ± 0.017[2] L☉
Surface gravity (log g)4.387 ± 0.014[2] cgs
Temperature5293 ± 32[2] K
Metallicity [Fe/H]0.16 ± 0.05[2] dex
Rotation~58.7 d
Age13.4 Gyr
Other designations
BD +26°3151, GJ 700.2, LFT 1388, SAO 85678, HIP 88348
Database references
SIMBADdata

HD 164922 is a seventh magnitude G-type main sequence star in the constellation of Hercules. To view it, binoculars or a telescope are necessary, as it is too faint to be visible to the naked eye. It is 72 light years distant from the Earth.[1] At an age of 13.4 billion years, it will soon evolve away from the main-sequence and expand to become a red giant. It is one of the oldest known stars in the Universe and one of the most ancient objects known in the Milky Way.

Nomenclature

The designation b derive from the order of discovery. The designation of b is given to the first planet orbiting a given star, followed by the other lowercase letters of the alphabet.[3] In the case of HD 164922, only one was discovered, which was designated b, then a more inner planet, which was designated c.[2] The name HD 164922 derives directly from the fact that the star is the 164,922nd star discovered in the Henry Draper catalog.

Stellar characteristics

HD 164922 is a G-type main sequence star that is approximately 87% the mass of and 99% the radius of the Sun. It has a temperature of 5293 K and is 13.4 billion years old. In comparison, the Sun is about 4.6 billion years old[4] and has a temperature of 5778 K.[5]

The star is metal-rich, with a metallicity ([Fe/H]) of 0.16, or 144% the solar amount. This is particularly odd for a star as old as HD 164922. Its luminosity (L☉) is 70% of the solar luminosity.[2]

Planetary system

The HD 164922 planetary system[6][2]
Companion
(in order from star) 		Mass Semimajor axis
(AU) 		Orbital period
(days) 		Eccentricity Inclination Radius
c ≥12.9 ± 1.6 M🜨 0.3351 ± 0.0015 75.765 0.07 — —
b ≥0.360 ± 0.046 MJ 2.11 ± 0.13 1155 ± 23 0.05 ± 0.14 — —

On 15 July 2006, a long period Saturn-mass exoplanet was announced orbiting around HD 164922. This planet orbits at 2.11 AU from the star with a low eccentricity value of 0.05.[6]

Almost exactly ten years later in 2016, another exoplanet, though less massive then the first planet, was discovered orbiting farther in from the star. This planet has a minimum mass of nearly 13 times that of Earth, meaning it is possibly a Neptune-like planet.

References

  1. ^ a b c d e f van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv:0708.1752. Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.Vizier catalog entry
  2. ^ a b c d e f g h i j Fulton, Benjamin J.; Howard, Andrew W.; Weiss, Lauren M.; Sinukoff, Evan; Petigura, Erik A.; Isaacson, Howard; Hirsch, Lea; Marcy, Geoffrey W.; Henry, Gregory W.; Grunblatt, Samuel K.; Huber, Daniel; Kaspar von Braun; Boyajian, Tabetha S.; Kane, Stephen R.; Wittrock, Justin; Horch, Elliott P.; Ciardi, David R.; Howell, Steve B.; Wright, Jason T.; Ford, Eric B. (2016). "Three Temperate Neptunes Orbiting Nearby Stars". The Astrophysical Journal. 830: 46. arXiv:1607.00007. Bibcode:2016ApJ...830...46F. doi:10.3847/0004-637X/830/1/46. {{cite journal}}: Unknown parameter |class= ignored (help)CS1 maint: unflagged free DOI (link)
  3. ^ Hessman, F. V.; Dhillon, V. S.; Winget, D. E.; Schreiber, M. R.; Horne, K.; Marsh, T. R.; Guenther, E.; Schwope, A.; Heber, U. (2010). "On the naming convention used for multiple star systems and extrasolar planets". arXiv:1012.0707 [astro-ph.SR].
  4. ^ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
  5. ^ Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
  6. ^ a b Butler, R. P.; Wright, J. T.; Marcy, G. W.; Fischer, D. A.; Vogt, S. S.; Tinney, C. G.; Jones, H. R. A.; Carter, B. D.; Johnson, J. A.; McCarthy, C.; Penny, A. J. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal. 646 (1): 505–522. arXiv:astro-ph/0607493. Bibcode:2006ApJ...646..505B. doi:10.1086/504701. {{cite journal}}: Unknown parameter |displayauthors= ignored (|display-authors= suggested) (help)



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