Alpha Aquarii

Alpha Aquarii
	Location of α Aquarii (circled)
Observation data; Epoch J2000.0 Equinox J2000.0 (ICRS)
Constellation	Aquarius
Right ascension	22h 05m 47.03555s
Declination	−00° 19′ 11.4634″
Apparent magnitude (V)	2.942
Characteristics
Evolutionary stage	Yellow supergiant
Spectral type	G2 Ib
U−B color index	+0.699
B−V color index	+0.971
R−I color index	+0.49
Astrometry
Radial velocity (Rv)	7.5 km/s
Proper motion (μ)	RA: +18.59 mas/yr ; Dec.: −10.45 mas/yr
Parallax (π)	4.9451 ± 0.4296 mas
Distance	691.1+37.8; −56.1 ly ; (211.9+11.6; −17.2 pc)
Absolute magnitude (MV)	−3.882
Details
Mass	6.31 M☉
Radius	70 R☉
Luminosity	3,917 L☉
Surface gravity (log g)	1.4 cgs
Temperature	5,190±50 K
Metallicity [Fe/H]	+0.17 dex
Rotational velocity (v sin i)	6.7±1.5 km/s
Age	53 Myr
Other designations
	El Melik, Rucbah, Saad el Melik, Sadalmelek, Sadalmelik, Sadlamulk, α Aqr, Alpha Aquarii, Alpha Aqr, 34 Aquarii, 34 Aqr, BD−01 4246, FK5 827, Gaia DR2 2680356911815074432, HD 209750, HIP 109074, HR 8414, SAO 145862, WDS 22058-0019, 2MASS J22054703-0019114
Database references
SIMBAD	data

Alpha Aquarii, officially named Sadalmelik (/ˌsædəlˈmɛlɪk/),^[15] is a single yellow supergiant star in the constellation of Aquarius. The apparent visual magnitude of 2.94^[2] makes this the second-brightest star in Aquarius. Based upon parallax measurements made by the Gaia spacecraft, it is located at a distance of roughly 690 light-years (210 parsecs) from the Sun.^[5] It is drifting further away from the Sun with a radial velocity of 7.5 km/s.^[4]

It forms the primary or 'A' component of a double star designated WDS J22058-0019; the secondary or 'B' component is UCAC2 31789179.^[16] However, the pair is only an optical binary, with UCAC2 31789179 being a background star.^[16]

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.^[17] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)^[18] 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, 危宿 (Wēi Xiù), meaning Rooftop (asterism), refers to an asterism consisting of Alpha Aquarii, Theta Pegasi and Epsilon Pegasi.^[19] Consequently, the Chinese name for Alpha Aquarii itself is 危宿一 (Wēi Xiù yī, English: the First Star of Rooftop).^[20]

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.^[21]

There is some uncertainty about Alpha Aquarii's distance. The original Hipparcos catalog gave a parallax of 4.3±0.83 mas, which translates to a distance of 233±45 parsecs, or 760 light-years.^[22] However, the 2007 Hipparcos reduction give a parallax that implies a distance of 161±5 pc, or 520 light-years.^[23] The third Gaia data release (Gaia DR3) give a parallax of 4.94±0.43 mas, translating to a distance of 202±17 pc, or 660 light-years.^[1]

Alpha Aquarii's angular diameter has been measured at 3.066±0.036 mas.^[24] At its estimated distance,^[5] it translates to a radius of 70 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.^[25] It is radiating 3,900 times as much luminosity as the Sun from its outer atmosphere^[7] at an effective temperature of 5,190 K.^[9] At this heat, the star glows with the yellow hue of a G-type star.^[26] 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]

The visual companion (UCAC2 31789179) has an apparent visual magnitude of approximately 12.2. It is at an angular separation of 110.4 arcseconds from Alpha Aquarii along a position angle of 40°.^[13]

References

^ ^a ^b ^c ^d ^e 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 Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars, 8: 59, Bibcode:1984SAAOC...8...59C
^ ^a ^b ^c ^d Lyubimkov, Leonid S.; et al. (February 2010), "Accurate fundamental parameters for A-, F- and G-type Supergiants in the solar neighbourhood", Monthly Notices of the Royal Astronomical Society, 402 (2): 1369–1379, arXiv:0911.1335, Bibcode:2010MNRAS.402.1369L, doi:10.1111/j.1365-2966.2009.15979.x, S2CID 119096173
^ ^a ^b Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W
^ ^a ^b ^c Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Demleitner, M.; Andrae, R. (2021-03-01). "Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3". The Astronomical Journal. 161 (3): 147. arXiv:2012.05220. Bibcode:2021AJ....161..147B. doi:10.3847/1538-3881/abd806. ISSN 0004-6256. Data about this star can be seen here.
^ ^a ^b Soubiran, C.; et al. (2008). "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants". Astronomy and Astrophysics. 480 (1): 91–101. arXiv:0712.1370. Bibcode:2008A&A...480...91S. doi:10.1051/0004-6361:20078788. S2CID 16602121.
^ ^a ^b ^c ^d Ayres, Thomas (2023-05-01). "In the Trenches of the Solar-Stellar Connection. VII. Wilson-Bappu 2022". The Astrophysical Journal Supplement Series. 266 (1): 6. Bibcode:2023ApJS..266....6A. doi:10.3847/1538-4365/acb535. ISSN 0067-0049. Alpha Aquarii's database entry at VizieR.
^ ^a ^b Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:
${\begin{aligned}2\cdot R_{*}&={\frac {(211.9\cdot 3.066\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 140\cdot R_{\bigodot }\end{aligned}}$
^ ^a ^b ^c Usenko, I. A.; et al. (November 2017), "Spectroscopic studies of the unique yellow supergiant α Aqr in the Cepheid instability strip", Astronomy Letters, 43 (11): 751–767, Bibcode:2017AstL...43..751U, doi:10.1134/S1063773717110068, S2CID 41734976.
^ ^a ^b Ayres, Thomas R.; Brown, Alexander; Harper, Graham M. (July 2005), "Chandra Observations of Coronal Emission from the Early G Supergiants α and β Aquarii", The Astrophysical Journal, 627 (1): L53 – L56, Bibcode:2005ApJ...627L..53A, doi:10.1086/431977, S2CID 122519436
^ HR 8414, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line October 3, 2008.
^ "Alpha Aquarii". SIMBAD. Centre de données astronomiques de Strasbourg.
^ ^a ^b Entry 22058-0019, The Washington Double Star Catalog Archived 2009-01-31 at the Wayback Machine, United States Naval Observatory. Accessed on line November 18, 2008.
^ ^a ^b pp. 51, 148, Star-names and Their Meanings, Richard Hinckley Allen, New York: G. E. Stechert, 1899.
^ ^a ^b "Naming Stars". IAU.org. Retrieved 25 February 2018.
^ ^a ^b "UCAC2 31789179 -- Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2018-02-25
^ Sadalmelik, Stars, Jim Kaler. Accessed on line October 3, 2008.
^ IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
^ (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.
^ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2010-08-18 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
^ Dupree, A. K.; et al. (December 1993), "HST/GHRS Spectroscopy of the Hybrid Star Alpha Aquarii", Bulletin of the American Astronomical Society, 25, American Astronomical Society, 183rd AAS Meeting: 1321, Bibcode:1993AAS...183.1807D, 18.07.
^ ESA (1997-01-01). "The HIPPARCOS and TYCHO catalogues. Astrometric and photometric star catalogues derived from the ESA HIPPARCOS Space Astrometry Mission". ESA Special Publication. 1200. Bibcode:1997ESASP1200.....E. ISSN 1609-042X.
^ van Leeuwen, F. (November 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, S2CID 18759600
^ Baines, Ellyn K.; Clark III, James H.; Schmitt, Henrique R.; Stone, Jordan M.; von Braun, Kaspar (2023-12-01). "33 New Stellar Angular Diameters from the NPOI, and Nearly 180 NPOI Diameters as an Ensemble". The Astronomical Journal. 166 (6): 268. Bibcode:2023AJ....166..268B. doi:10.3847/1538-3881/ad08be. ISSN 0004-6256.
^ "Sadalsuud". stars.astro.illinois.edu. Retrieved 2024-08-04.
^ "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on February 22, 2012, retrieved 2012-01-16

External links

Alpha Aquarii Aladin image viewer

[DR3-1] 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.

[saoc8_59-2] Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars, 8: 59, Bibcode:1984SAAOC...8...59C

[mnras402_2_1369-3] Lyubimkov, Leonid S.; et al. (February 2010), "Accurate fundamental parameters for A-, F- and G-type Supergiants in the solar neighbourhood", Monthly Notices of the Royal Astronomical Society, 402 (2): 1369–1379, arXiv:0911.1335, Bibcode:2010MNRAS.402.1369L, doi:10.1111/j.1365-2966.2009.15979.x, S2CID 119096173

[scfs-4] Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W

[b-j-5] Bailer-Jones, C. A. L.; Rybizki, J.; Fouesneau, M.; Demleitner, M.; Andrae, R. (2021-03-01). "Estimating distances from parallaxes. V: Geometric and photogeometric distances to 1.47 billion stars in Gaia Early Data Release 3". The Astronomical Journal. 161 (3): 147. arXiv:2012.05220. Bibcode:2021AJ....161..147B. doi:10.3847/1538-3881/abd806. ISSN 0004-6256. Data about this star can be seen here.

[aaa480_1_91-6] Soubiran, C.; et al. (2008). "Vertical distribution of Galactic disk stars. IV. AMR and AVR from clump giants". Astronomy and Astrophysics. 480 (1): 91–101. arXiv:0712.1370. Bibcode:2008A&A...480...91S. doi:10.1051/0004-6361:20078788. S2CID 16602121.

[Ayres2023-7] Ayres, Thomas (2023-05-01). "In the Trenches of the Solar-Stellar Connection. VII. Wilson-Bappu 2022". The Astrophysical Journal Supplement Series. 266 (1): 6. Bibcode:2023ApJS..266....6A. doi:10.3847/1538-4365/acb535. ISSN 0067-0049. Alpha Aquarii's database entry at VizieR.

[lang2006-8] Lang, Kenneth R. (2006), Astrophysical formulae, Astronomy and astrophysics library, vol. 1 (3rd ed.), Birkhäuser, ISBN 3-540-29692-1. The radius (R_*) is given by:
${\begin{aligned}2\cdot R_{*}&={\frac {(211.9\cdot 3.066\cdot 10^{-3})\ {\text{AU}}}{0.0046491\ {\text{AU}}/R_{\bigodot }}}\\&\approx 140\cdot R_{\bigodot }\end{aligned}}$

[Usenko_et_al_2017-9] Usenko, I. A.; et al. (November 2017), "Spectroscopic studies of the unique yellow supergiant α Aqr in the Cepheid instability strip", Astronomy Letters, 43 (11): 751–767, Bibcode:2017AstL...43..751U, doi:10.1134/S1063773717110068, S2CID 41734976.

[apj627_1_L53-10] Ayres, Thomas R.; Brown, Alexander; Harper, Graham M. (July 2005), "Chandra Observations of Coronal Emission from the Early G Supergiants α and β Aquarii", The Astrophysical Journal, 627 (1): L53 – L56, Bibcode:2005ApJ...627L..53A, doi:10.1086/431977, S2CID 122519436

[bsc1-11] HR 8414, database entry, The Bright Star Catalogue, 5th Revised Ed. (Preliminary Version), D. Hoffleit and W. H. Warren, Jr., CDS ID V/50. Accessed on line October 3, 2008.

[sb0-12] "Alpha Aquarii". SIMBAD. Centre de données astronomiques de Strasbourg.

[wds-13] Entry 22058-0019, The Washington Double Star Catalog Archived 2009-01-31 at the Wayback Machine, United States Naval Observatory. Accessed on line November 18, 2008.

[allen-14] . 51, 148, Star-names and Their Meanings, Richard Hinckley Allen, New York: G. E. Stechert, 1899.

[IAU-LSN-15] "Naming Stars". IAU.org. Retrieved 25 February 2018.

[SIMBAD2-16] "UCAC2 31789179 -- Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2018-02-25

[kaler-17] Sadalmelik, Stars, Jim Kaler. Accessed on line October 3, 2008.

[WGSN-18] IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.

[19] (in Chinese) 中國星座神話, written by 陳久金. Published by 台灣書房出版有限公司, 2005, ISBN 978-986-7332-25-7.

[20] (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2010-08-18 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.

[Dupree_et_al_1993-21] Dupree, A. K.; et al. (December 1993), "HST/GHRS Spectroscopy of the Hybrid Star Alpha Aquarii", Bulletin of the American Astronomical Society, 25, American Astronomical Society, 183rd AAS Meeting: 1321, Bibcode:1993AAS...183.1807D, 18.07.

[hipparcos1997-22] ESA (1997-01-01). "The HIPPARCOS and TYCHO catalogues. Astrometric and photometric star catalogues derived from the ESA HIPPARCOS Space Astrometry Mission". ESA Special Publication. 1200. Bibcode:1997ESASP1200.....E. ISSN 1609-042X.

[aaa474_2_653-23] van Leeuwen, F. (November 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, S2CID 18759600

[Baines2023-24] Baines, Ellyn K.; Clark III, James H.; Schmitt, Henrique R.; Stone, Jordan M.; von Braun, Kaspar (2023-12-01). "33 New Stellar Angular Diameters from the NPOI, and Nearly 180 NPOI Diameters as an Ensemble". The Astronomical Journal. 166 (6): 268. Bibcode:2023AJ....166..268B. doi:10.3847/1538-3881/ad08be. ISSN 0004-6256.

[25] "Sadalsuud". stars.astro.illinois.edu. Retrieved 2024-08-04.

[csiro-26] "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on February 22, 2012, retrieved 2012-01-16

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Alpha Aquarii

Nomenclature

Properties

References

External links

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