Alpha Delphini

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α Delphini A
Delphinus constellation map.svg
Red circle.svg

Location of α Delphini (circled)
Observation data
Epoch J2000.0      Equinox J2000.0
Constellation Delphinus
Right ascension 20h 39m 38.28720s[1]
Declination +15° 54′ 43.4637″[1]
Apparent magnitude (V) +3.777[2] (3.86 + 6.43[3])
Characteristics
Spectral type B9 IV[4]
U−B color index −0.205[2]
B−V color index −0.061[2]
Astrometry
Radial velocity (Rv) −3.40[5] km/s
Proper motion (μ) RA: 53.82 ± 0.43[1] mas/yr
Dec.: 8.47 ± 0.31[1] mas/yr
Parallax (π) 12.85 ± 0.44[1] mas
Distance 254 ± 9 ly
(78 ± 3 pc)
Absolute magnitude (MV) −0.4[6]
Orbit
Period (P) 17.0[3] yr
Semi-major axis (a) 0.158[3]
Eccentricity (e) 0.47[3]
Details
α Del Aa
Mass 2.82[3] M
Radius 3.92[7] R
Surface gravity (log g) 3.93[8] cgs
Temperature 11,643[8] K
Rotational velocity (v sin i) 144[8] km/s
Age 227[8] Myr
Other designations
α Del, 9 Delphini, BD+15 4222, HD 196867, HIP 101958, HR 7906, SAO 106357, CCDM J20396+1555, WDS J20396+1555
Database references
SIMBAD data

Alpha Delphini (α Delphini, abbreviated Alpha Del, α Del), also named Sualocin,[9] is a multiple star in the constellation of Delphinus.

Nomenclature[edit]

α Delphini (Latinised to Alpha Delphini) is the star's Bayer designation.

It bore an historical name, Sualocin, which arose as follows: Niccolò Cacciatore was the assistant to Giuseppe Piazzi, and later his successor as Director of the Palermo Observatory. The name first appeared in Piazzi's Palermo Star Catalogue. When the Catalogue was published in 1814, the unfamiliar names Sualocin and Rotanev were attached to Alpha and Beta Delphini, respectively. Eventually the Reverend Thomas Webb, a British astronomer, puzzled out the explanation.[10] Cacciatore's name, Nicholas Hunter in English translation, would be Latinized to Nicolaus Venator. Reversing the letters of this construction produces the two star names. They have endured, the result of Cacciatore's little practical joke of naming the two stars after himself. How Webb arrived at this explanation 45 years after the publication of the catalogue is still a mystery.[11]

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[12] to catalogue and standardize proper names for stars. The WGSN approved the name Sualocin for Alpha Delphini on 12 September 2016 and it is now so entered in the IAU Catalog of Star Names.[9]

In Chinese, 瓠瓜 (Hù Guā), meaning Good Gourd, refers to an asterism consisting of Alpha Delphini, Gamma2 Delphini, Delta Delphini, Beta Delphini and Zeta Delphini.[13] Consequently, Alpha Delphini itself is known as 瓠瓜一 (Hù Guā yī, English: the First Star of Good Gourd.).[14]

In Hindu astronomy, the star corresponded to one of the nakshatras named Dhanishta.

Companions[edit]

α Delphini is a spectroscopic binary star which has now been resolved using speckle interferometry. The components are referred to as Aa and Ab,[15] or sometimes as A and G.[16] They are separated by 0.2" and have a 17 year orbit.

In addition, there are five faint listed in multiple star catalogues. They have visual magnitudes around 11th to 13th magnitude and separations of 35" to 72". They all show motion relative to α Delphini A and are likely to be only optical companions.[15][16]

Properties[edit]

α Delphini Aa has a spectral type of B9IV. The spectral type of the secondary star cannot be determined as it is too close and too faint compared to the primary, and its other properties are also unknown. The primary is a subgiant that has begun to evolve away from the main sequence. It is 2.82 times as massive as the sun and about twice as hot.

References[edit]

  1. ^ a b c d e van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653–664. Bibcode:2007A&A...474..653V. arXiv:0708.1752Freely accessible. doi:10.1051/0004-6361:20078357. Vizier catalog entry
  2. ^ a b c Oja, T. (1991). "UBV photometry of stars whose positions are accurately known. VI". Astronomy and Astrophysics Supplement Series (ISSN 0365-0138). 89: 415. Bibcode:1991A&AS...89..415O. 
  3. ^ a b c d e Malkov, O. Yu.; Tamazian, V. S.; Docobo, J. A.; Chulkov, D. A. (2012). "Dynamical masses of a selected sample of orbital binaries". Astronomy & Astrophysics. 546: A69. Bibcode:2012A&A...546A..69M. doi:10.1051/0004-6361/201219774. 
  4. ^ Morgan, W. W.; Keenan, P. C. (1973). "Spectral Classification". Annual Review of Astronomy and Astrophysics. 11: 29. Bibcode:1973ARA&A..11...29M. doi:10.1146/annurev.aa.11.090173.000333. 
  5. ^ Kharchenko, N. V.; Scholz, R.-D.; Piskunov, A. E.; Röser, S.; Schilbach, E. (2007). "Astrophysical supplements to the ASCC-2.5: Ia. Radial velocities of ˜55000 stars and mean radial velocities of 516 Galactic open clusters and associations". Astronomische Nachrichten. 328 (9): 889. Bibcode:2007AN....328..889K. arXiv:0705.0878Freely accessible. doi:10.1002/asna.200710776. 
  6. ^ Jaschek, C.; Gomez, A. E. (1998). "The absolute magnitude of the early type MK standards from HIPPARCOS parallaxes". Astronomy and Astrophysics. 330: 619. Bibcode:1998A&A...330..619J. 
  7. ^ Fitzpatrick, E. L.; Massa, D. (2005). "Determining the Physical Properties of the B Stars. II. Calibration of Synthetic Photometry". The Astronomical Journal. 129 (3): 1642. Bibcode:2005AJ....129.1642F. arXiv:astro-ph/0412542Freely accessible. doi:10.1086/427855. 
  8. ^ a b c d David, Trevor J.; Hillenbrand, Lynne A. (2015). "The Ages of Early-type Stars: Strömgren Photometric Methods Calibrated, Validated, Tested, and Applied to Hosts and Prospective Hosts of Directly Imaged Exoplanets". The Astrophysical Journal. 804 (2): 146. Bibcode:2015ApJ...804..146D. arXiv:1501.03154Freely accessible. doi:10.1088/0004-637X/804/2/146. 
  9. ^ a b "IAU Catalog of Star Names". Retrieved 28 July 2016. 
  10. ^ Webb, T.W. (1859). Celestial Objects for Common Telescopes. London: Longmans, Green and Co. pp. 193–194. 
  11. ^ Hurn, Mark. "Secrets of the 1814 Palermo Star Catalogue". The Story of Star Names. Mark Hurn, Institute of Astronomy Library, Univ. of Cambridge. Archived from the original on 4 March 2016. Retrieved 11 May 2015. 
  12. ^ "IAU Working Group on Star Names (WGSN)". International Astronomical Union. Retrieved 22 May 2016. 
  13. ^ 陳久金 (2005). 中國星座神話. 五南圖書出版股份有限公司. ISBN 978-986-7332-25-7. 
  14. ^ (in Chinese)"香港太空館 - 研究資源 - 亮星中英對照表". Hong Kong Space Museum. Archived from the original on August 18, 2010. Retrieved November 23, 2010. 
  15. ^ a b Mason, Brian D.; Wycoff, Gary L.; Hartkopf, William I.; Douglass, Geoffrey G.; Worley, Charles E. (2001). "The 2001 US Naval Observatory Double Star CD-ROM. I. The Washington Double Star Catalog". The Astronomical Journal. 122 (6): 3466. Bibcode:2001AJ....122.3466M. doi:10.1086/323920. 
  16. ^ a b Dommanget, J.; Nys, O. (1994). "Catalogue des composantes d'etoiles doubles et multiples (CCDM) premiere edition - Catalogue of the components of double and multiple stars (CCDM) first edition". Com. de l'Observ. Royal de Belgique. 115: 1. Bibcode:1994CoORB.115....1D.