HD 164922 c
{{Short description|Extrasolar planet in the constellation Hercules}}
{{Infobox planet
| name = HD 164922 c
| discoverer = W. M. Keck Observatory
| discovered = 30 June 2016
| discovery_method = radial velocity
| apsis = astron
| semimajor = 0.3351 (± 0.0015){{cite journal|arxiv=1607.00007|last1= Fulton|first1= Benjamin J.|title= Three Temperate Neptunes Orbiting Nearby Stars|last2= Howard|first2= Andrew W.|last3= Weiss|first3= Lauren M.|last4= Sinukoff|first4= Evan|last5= Petigura|first5= Erik A.|last6= Isaacson|first6= Howard|last7= Hirsch|first7= Lea|last8= Marcy|first8= Geoffrey W.|last9= Henry|first9= Gregory W.|last10= Grunblatt|first10= Samuel K.|last11= Huber|first11= Daniel|author12= Kaspar von Braun|last13= Boyajian|first13= Tabetha S.|last14= Kane|first14= Stephen R.|last15= Wittrock|first15= Justin|last16= Horch|first16= Elliott P.|last17= Ciardi|first17= David R.|last18= Howell|first18= Steve B.|last19= Wright|first19= Jason T.|last20= Ford|first20= Eric B.|year= 2016|doi=10.3847/0004-637X/830/1/46|volume=830|issue= 1|journal=The Astrophysical Journal|page=46|bibcode = 2016ApJ...830...46F |s2cid= 36666883|doi-access= free}} AU
| eccentricity = {{val|0.079|0.089|0.066}}
| period = {{val|75.765|0.058|0.056}} d
| time_periastron = 2456277.6 ± 2.7
| star = HD 164922
| mean_radius = ~3.5 {{Earth radius|link=y}}
| single_temperature = {{convert|400|K|C F}}
}}
HD 164922 c is an exoplanet orbiting the star HD 164922 about 72 light-years from Earth in the constellation Hercules. The exoplanet was found by using the radial velocity method, from radial-velocity measurements via observation of Doppler shifts in the spectrum of the planet's parent star.
Characteristics
=Mass, radius and temperature=
HD 164922 c is a mini-Neptune, an exoplanet that has a radius and mass in between that of a super-Earth and the planet Neptune with no solid surface. It has a temperature of {{convert|400|K|C F}}. It has an estimated mass of around 12.9 {{Earth mass|sym=y|link=y}}, and a potential radius of around 3.5 {{Earth radius|link=y}} based on its similar mass to Neptune.
=Host star=
{{main|HD 164922}}
The planet orbits a (G-type) star named HD 164922. The star has a mass of 0.87 {{Solar mass|link=y}} and a radius of around 0.99 {{Solar radius|link=y}}. 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{{cite web |url=http://www.universetoday.com/18237/how-old-is-the-sun/ |title=How Old is the Sun? |author=Fraser Cain |date=16 September 2008 |publisher=Universe Today |access-date=19 February 2011}} and has a temperature of 5778 K.{{cite web |url=http://www.universetoday.com/18092/temperature-of-the-sun/ |title=Temperature of the Sun |author=Fraser Cain |date=September 15, 2008 |publisher=Universe Today |access-date=19 February 2011}} 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 ({{solar luminosity|link=y}}) is 70% of the solar luminosity.
The star's apparent magnitude, or how bright it appears from Earth's perspective, is 7.01. Therefore, HD 164922 is too dim to be seen with the naked eye, but can be viewed using good binoculars.
= Orbit =
Discovery
The search for HD 164922 c started when its host star was chosen an ideal target for a planet search using the radial velocity method (in which the gravitational pull of a planet on its star is measured by observing the resulting Doppler shift), as stellar activity would not overly mask or mimic Doppler spectroscopy measurements. It was also confirmed that HD 164922 is neither a binary star nor a quickly rotating star, common false positives when searching for transiting planets. Analysis of the resulting data found that the radial velocity variations most likely indicated the existence of a planet. The net result was an estimate of a 12.9 {{Earth mass|sym=y}} planetary companion orbiting the star at a distance of 0.33 AU with an eccentricity of 0.07.
The discovery of HD 164922 c was reported in the online archive arXiv on June 30, 2016.
See also
References
{{Reflist|refs=
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{{2016 in space|state=collapsed}}
{{Exoplanet}}
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Category:Exoplanets discovered in 2016