Alpha Aquarii

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Template:Short description

Alpha Aquarii
Template:Location mark
Location of α Aquarii (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Aquarius
Right ascension Template:RA[1]
Declination Template:DEC[1]
Apparent magnitude (V) 2.942[2]
Characteristics
Evolutionary stage Yellow supergiant
Spectral type G2 Ib[3]
U−B Template:Engvar +0.699[2]
B−V Template:Engvar +0.971[2]
R−I Template:Engvar +0.49[2]
Astrometry
Radial velocity (Rv)7.5[4] km/s
Proper motion (μ) RA: +18.59 mas/yr[1]
Dec.: Template:Val mas/yr[1]
Parallax (π)4.9451±0.4296 mas[1]
DistanceTemplate:Val ly
(Template:Val pc)[5]
Absolute magnitude (MV)Template:Val[6]
Details
Mass6.31[7] Template:Solar mass
RadiusTemplate:Solar radius calculator[8] Template:Solar radius
Luminosity3,917[7] Template:Solar luminosity
Surface gravity (log g)1.4[7] cgs
TemperatureTemplate:Val[9] K
Metallicity [Fe/H]+0.17[6] dex
Rotational velocity (v sin i)Template:Val[10] km/s
Age53[3] Myr
Metallicity [Fe/H]{{{metal_fe2}}} dex
Other designations
Template:Odlist[11][12][13][14]
Database references
SIMBADdata

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Alpha Aquarii is a yellow supergiant star in the constellation of Aquarius. Its identifier is a Bayer designation that is Latinized from α Aquarii, and is abbreviated Alf Aqr or α Aqr, respectively. This star has the official name Sadalmelik, pronounced Template:IPAc-en.[15] At an apparent visual magnitude of 2.94,[2] it is the second-brightest star in Aquarius, just marginally fainter than Beta Aquarii. Based upon parallax measurements made by the Gaia spacecraft, it is located at a distance of roughly Template:Convert.[5] It is drifting further away from the Sun with a radial velocity of 7.5 km/s.[4]

Nomenclature

α Aquarii (Latinised to Alpha Aquarii) is the star's Bayer designation. WDS J22058-0019 A is its designation in the Washington Double Star Catalog.

It bore the traditional name Sadalmelik, which derived from an Arabic expression سعد الملك (sa‘d al-malik), meaning "Luck of the king" or “arm/support of God”. The name Rucbah had also been applied to this star; though it shared that name with Delta Cassiopeiae.[14] It is only one of two stars with ancient proper names to lie within a degree of the celestial equator. The origin of the Arabic name is lost to history.[16] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[17] to catalogue and standardize proper names for stars. The WGSN approved the name Sadalmelik for Alpha Aquarii (WDS J22058-0019 A) on 21 August 2016, and it is now so included in the List of IAU-approved Star Names (Delta Cassiopeiae was given the name Ruchbah).[15]

In Chinese, Script error: No such module "Lang". (Script error: No such module "Lang".), meaning Rooftop (asterism), refers to an asterism consisting of Alpha Aquarii, Theta Pegasi and Epsilon Pegasi.[18] Consequently, the Chinese name for Alpha Aquarii itself is Script error: No such module "Lang". (Script error: No such module "Lang"., Template:Langx).[19]

Properties

With an age of 53 million years,[3] Alpha Aquarii has evolved into a supergiant with a stellar classification of G2 Ib.[3] It lies within the Cepheid instability strip of the Hertzsprung–Russell diagram, near the red (cooler) edge, but is not classified as a variable star. However, variable cores have been detected in the hydrogen lines, which are originating in a circumstellar envelope.[9] The star has a massive stellar wind that reaches supersonic velocity in the chromosphere.[20]

There is some uncertainty about Alpha Aquarii's distance. The original Hipparcos catalog gave a parallax of Template:Val, which translates to a distance of Template:Val, or 760 light-years.[21] However, the 2007 Hipparcos reduction give a parallax that implies a distance of Template:Val, or 520 light-years.[22] The third Gaia data release (Gaia DR3) give a parallax of Template:Val, translating to a distance of Template:Val, or 660 light-years.[1]

Alpha Aquarii's angular diameter has been measured at Template:Val.[23] This diameter, at its estimated distance,[5] translates to a radius of Template:Solar radius calculator times the radius of the Sun.[8] With insufficient mass to explode as a supernova, it will most likely become a massive white dwarf similar to Sirius B.[16] It is radiating 3,900 times as much luminosity as the Sun from its outer atmosphere[7] at an effective temperature of Template:Val.[9] At this heat, the star glows with the yellow hue of a G-type star.[24] Examination of this star with the Chandra X-ray Observatory shows it to be significantly X-ray deficient compared to G-type main-sequence stars. This deficit is a common feature of early G-type giant stars.[10]

Alpha Aquarii has a visual companion, UCAC2 31789179, of magnitude 12.2. It is at an angular separation of 110.4 arcseconds from Alpha Aquarii along a position angle of 40°.[13] However, the pair is only a visual double, with UCAC2 31789179 being a background star.[25]

References

Template:Reflist

External links

Template:Sky Template:Stars of Aquarius

  1. ↑ a b c d e Cite error: Invalid <ref> tag; no text was provided for refs named DR3
  2. ↑ a b c d e Cite error: Invalid <ref> tag; no text was provided for refs named saoc8_59
  3. ↑ a b c d Cite error: Invalid <ref> tag; no text was provided for refs named mnras402_2_1369
  4. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named scfs
  5. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named b-j
  6. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named aaa480_1_91
  7. ↑ a b c d Cite error: Invalid <ref> tag; no text was provided for refs named Ayres2023
  8. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named lang2006
  9. ↑ a b c Cite error: Invalid <ref> tag; no text was provided for refs named Usenko_et_al_2017
  10. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named apj627_1_L53
  11. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named bsc1
  12. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named sb0
  13. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named wds
  14. ↑ a b pp. 51, 148, Star-names and Their Meanings, Richard Hinckley Allen, New York: G. E. Stechert, 1899.
  15. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named IAU-LSN
  16. ↑ a b Cite error: Invalid <ref> tag; no text was provided for refs named kaler
  17. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named WGSN
  18. ↑ Template:In lang 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, Template:ISBN.
  19. ↑ Template:In lang 香港太空館 - 研究資源 - 亮星中英對照表 Template:Webarchive, Hong Kong Space Museum. Accessed on line November 23, 2010.
  20. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Dupree_et_al_1993
  21. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named hipparcos1997
  22. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named aaa474_2_653
  23. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named Baines2023
  24. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named csiro
  25. ↑ Cite error: Invalid <ref> tag; no text was provided for refs named SIMBAD2
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