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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 30.86234s
Declination	+26° 18′ 46.8050″
Apparent magnitude (V)	+6.99
Characteristics
Spectral type	G9V
B−V color index	0.799±0.005
Astrometry
Radial velocity (Rv)	20.16±0.12 km/s
Proper motion (μ)	RA: 389.772 mas/yr ; Dec.: -602.431 mas/yr
Parallax (π)	45.4954 ± 0.0167 mas
Distance	71.69 ± 0.03 ly ; (21.980 ± 0.008 pc)
Details
Mass	0.874 ± 0.012 M☉
Radius	0.999 ± 0.017 R☉
Luminosity	0.703 ± 0.017 L☉
Surface gravity (log g)	4.387 ± 0.014 cgs
Temperature	5390±30 K
Metallicity [Fe/H]	0.16 ± 0.05 dex
Rotation	42.3+1.3; −0.7 d
Rotational velocity (v sin i)	<2.0 km/s
Age	13.4, 9.58+1.99; −1.55 Gyr
Other designations
	BD +26°3151, GJ 700.2, LFT 1388, SAO 85678, HIP 88348, 2MASS J18023085+2618471
Database references
SIMBAD	data

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 71.7 light-years (22.0 parsecs) distant from the Earth.^[1] It will soon evolve away from the main-sequence and expand to become a red giant.^{[citation needed]}

Nomenclature

The name HD 164922 derives directly from the fact that the star is the 164,922nd star listed in the Henry Draper catalog. The designation b for its planet derives from the order of discovery. The designation of b is given to the first planet found orbiting a given star, followed by the other lowercase letters of the alphabet.^[5] In the case of HD 164922, only one was discovered, which was designated b, followed by three more planets, which were designated c, d, and e.^[3]^[6]

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 5390 K and is about 10 billion years old,^[2] with estimates ranging as high as 13.4 billion years.^[4] In comparison, the Sun is about 4.6 billion years old^[7] and has a temperature of 5778 K.^[8]

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.^[3]

Planetary system

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.^[9]

Almost exactly ten years later in 2016, another exoplanet, though less massive than 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.^[3]

A third exoplanet, a hot super-Earth, was discovered in 2020,^[2] and a fourth, Neptune-mass, in 2021.^[6]

The HD 164922 planetary system^[6]^[10]
Companion (in order from star)	Mass	Semimajor axis (AU)	Orbital period (days)	Eccentricity	Inclination	Radius
d	≥4.74±0.67 $M$ _🜨	0.1023±0.0012	12.4584+0.0019 −0.0023	0.18+0.17 −0.12	—	—
e	≥10.52+0.99 −0.97 $M$ _🜨	0.2292+0.0026 −0.0027	41.763±0.012	0.086+0.083 −0.060	—	—
c	≥14.3±1.1 $M$ _🜨	0.3411±0.0039	75.817+0.037 −0.038	0.096+0.088 −0.066	—	—
b	≥0.344±0.013 $M$ _J	2.149±0.025	1,198.5+3.2 −3.1	0.065+0.027 −0.029	—	—

References

^ ^a ^b ^c ^d ^e ^f Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
^ ^a ^b ^c ^d ^e ^f ^g ^h Benatti, S.; Damasso, M.; Desidera, S.; Marzari, F.; Biazzo, K.; Claudi, R.; Di Mauro, M. P.; Lanza, A. F.; Pinamonti, M.; Barbato, D.; Malavolta, L.; Poretti, E.; Sozzetti, A.; Affer, L.; Bignamini, A.; Bonomo, A. S.; Borsa, F.; Brogi, M.; Bruno, G.; Carleo, I.; Cosentino, R.; Covino, E.; Frustagli, G.; Giacobbe, P.; Gonzalez, M.; Gratton, R.; Harutyunyan, A.; Knapic, C.; Leto, G.; et al. (2020). "The GAPS Programme at TNG -- XXIII. HD 164922 d: a close-in super-Earth discovered with HARPS-N in a system with a long-period Saturn mass companion". Astronomy & Astrophysics. 639: A50. arXiv:2005.03368. Bibcode:2020A&A...639A..50B. doi:10.1051/0004-6361/202037939. S2CID 218538033.
^ ^a ^b ^c ^d ^e ^f ^g ^h ⁱ 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 (1): 46. arXiv:1607.00007. Bibcode:2016ApJ...830...46F. doi:10.3847/0004-637X/830/1/46. S2CID 36666883.
^ ^a ^b Takeda, Genya; et al. (February 2007). "Structure and Evolution of Nearby Stars with Planets. II. Physical Properties of ~1000 Cool Stars from the SPOCS Catalog". The Astrophysical Journal Supplement Series. 168 (2): 297–318. arXiv:astro-ph/0607235. Bibcode:2007ApJS..168..297T. doi:10.1086/509763. S2CID 18775378. Retrieved 2011-08-26.
^ 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].
^ ^a ^b ^c Rosenthal, Lee J.; Fulton, Benjamin J.; Hirsch, Lea A.; Isaacson, Howard T.; Howard, Andrew W.; Dedrick, Cayla M.; Sherstyuk, Ilya A.; Blunt, Sarah C.; Petigura, Erik A.; Knutson, Heather A.; Behmard, Aida; Chontos, Ashley; Crepp, Justin R.; Crossfield, Ian J. M.; Dalba, Paul A.; Fischer, Debra A.; Henry, Gregory W.; Kane, Stephen R.; Kosiarek, Molly; Marcy, Geoffrey W.; Rubenzahl, Ryan A.; Weiss, Lauren M.; Wright, Jason T. (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
^ Fraser Cain (16 September 2008). "How Old is the Sun?". Universe Today. Retrieved 19 February 2011.
^ Fraser Cain (15 September 2008). "Temperature of the Sun". Universe Today. Retrieved 19 February 2011.
^ Butler, R. P.; et al. (2006). "Catalog of Nearby Exoplanets". The Astrophysical Journal. 646 (1): 505–522. arXiv:astro-ph/0607493. Bibcode:2006ApJ...646..505B. doi:10.1086/504701. S2CID 119067572.
^ "HD 164922". NASA Exoplanet Archive. Retrieved 1 March 2023.