Position of star HD 164922 in the constellation Hercules
Epoch J2000.0 Equinox J2000.0
|Right ascension||18h 02m 30.86s|
|Declination||+26° 18′ 46.81″|
|Apparent magnitude (V)||+7.01|
|U−B color index||0.47|
|B−V color index||0.80|
|V−R color index||0.42|
|R−I color index||0.36|
|Radial velocity (Rv)||+22.8 km/s|
|Proper motion (μ)||RA: 389.41 ± 0.36 mas/yr
Dec.: –602.03 ± 0.52 mas/yr
|Parallax (π)||45.21 ± 0.54 mas|
|Distance||72.1 ± 0.9 ly
(22.1 ± 0.3 pc)
|Absolute magnitude (MV)||5.31|
|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||5293 ± 32 K|
|Metallicity [Fe/H]||0.16 ± 0.05 dex|
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. 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.
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. In the case of HD 164922, only one was discovered, which was designated b, then a more inner planet, which was designated c. The name HD 164922 derives directly from the fact that the star is the 164,922nd star discovered in the Henry Draper catalog.
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 and has a temperature of 5778 K.
(in order from star)
|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||—||—|
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.
- van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. arXiv: . Bibcode:2007A&A...474..653V. doi:10.1051/0004-6361:20078357.Vizier catalog entry
- 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: [astro-ph.EP]. Bibcode:2016ApJ...830...46F. doi:10.3847/0004-637X/830/1/46.
- 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: [astro-ph.SR].
- 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: . Bibcode:2006ApJ...646..505B. doi:10.1086/504701.
- The Extrasolar Planet Encyclopedia: HD 164922
- SIMBAD: HD 164922
- "ARICNS: HD 164922". ARICNS. Centre of Astronomy, Heidelberg University.
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