Beta Delphini

Beta Delphini (β Delphini, abbreviated Beta Del, β Del) is a binary star in the constellation of Delphinus. It is the brightest star in Delphinus.

β Delphini
Location of β Delphini (circled)
Observation data
Epoch J2000      Equinox J2000
Constellation Delphinus
Right ascension  20h 37m 32.94130s[1]
Declination +14° 35′ 42.3195″[1]
Apparent magnitude (V) 3.617±0.016[2] (4.11 + 5.01)[3]
Characteristics
Spectral type F5 III + F5 IV[4]
B−V color index A: 0.43±0.14
B: 0.56±0.25[1]
Astrometry
Beta Delphini A
Proper motion (μ) RA: +118.09[1] mas/yr
Dec.: -48.06[1] mas/yr
Parallax (π)32.33 ± 0.47[1] mas
Distance101 ± 1 ly
(30.9 ± 0.4 pc)
Absolute magnitude (MV)1.58±0.12[2]
Beta Delphini B
Absolute magnitude (MV)2.79±0.14[2]
Orbit[3]
Period (P)26.660 yr
Semi-major axis (a)0.440″
Eccentricity (e)0.36
Inclination (i)61°
Longitude of the node (Ω)177°
Periastron epoch (T)1989.50 yr
Argument of periastron (ω)
(secondary)		349°
Semi-amplitude (K1)
(primary)		7.6[5] km/s
Details
Beta Delphini A
Mass1.75±0.002[2] M☉
Luminosity24[6] L☉
Surface gravity (log g)3.50[6] cgs
Temperature6587[6] K
Metallicity [Fe/H]–0.05[2] dex
Rotational velocity (v sin i)49.8[6] km/s
Age1.79+0.17
−0.72[2] Gyr
Beta Delphini B
Mass1.47±0.04[2] M☉
Luminosity8[7] L☉
Other designations
Rotanev, Rotanen, Venator, β Del, Beta Delphini, Beta Del, 6 Delphini, 6 Del, BD+14 4369, HD 196524, HIP 101769, HR 7882, SAO 106316, WDS 20375+1436AB.[8][9][10]
Database references
SIMBADdata

The two components of the system are designated Beta Delphini A (officially named Rotanev /ˈroʊtənɛv/, which is historically the name of the system)[11][12] and B.

Nomenclature

β Delphini (Latinised to Beta Delphini) is the binary's Bayer designation. The designations of the two components as Beta Delphini A and B derive from the convention used by the Washington Multiplicity Catalog (WMC) for multiple star systems, and adopted by the International Astronomical Union (IAU).[13]

Beta Delpini bore an historical name, Rotanev, 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.[14] Cacciatore's name, Nicholas Hunter in English translation, would be Latinized to Nicolaus Venator. Reversing the letters of this construction produces the two names. They have endured, the result of Cacciatore's little practical joke of naming the two after himself. How Webb arrived at this explanation 45 years after the publication of the catalogue is still a mystery.[15]

In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[16] to catalogue and standardize proper names for stars. The WGSN decided to attribute proper names to individual stars rather than entire multiple systems.[17] It approved the name Rotanev for the component Beta Delphini A on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.[12]

In Chinese, 瓠瓜 (Hù Guā), meaning Good Gourd, refers to an asterism consisting of Beta Delphini, Alpha Delphini, Gamma2 Delphini, Delta Delphini, and Zeta Delphini.[18]

Properties

Beta Delphini was found to be a binary star system in 1873 by the American astronomer S. W. Burnham.[19] The system consists of a pair of F-type stars that orbit each other with a period of 26.66 years and an eccentricity of 0.36. The plane of the orbit is inclined by an angle of 61° to the line of sight from the Earth. The two stars have an angular separation of about 0.44 arcseconds, making them a challenge to resolve with a telescope. The larger member of the pair is a giant star with 1.75 times the mass[2] and 24 times the luminosity of the Sun,[6] while the secondary component is a subgiant star that has 1.47 times the Sun's mass[2] and around 8 times the Sun's luminosity.[7] The system is around 1.8 billion years old.[2]

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See also
  • Sualocin and Rotanev

References
  1. 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
  2. Davidson, James W., Jr.; et al. (November 2009), "A Photometric Analysis of Seventeen Binary Stars Using Speckle Imaging", The Astronomical Journal, 138 (5): 1354–1364, Bibcode:2009AJ....138.1354D, doi:10.1088/0004-6256/138/5/1354
  3. Söderhjelm, Staffan (January 1999), "Visual binary orbits and masses post Hipparcos", Astronomy and Astrophysics, 341: 121–140, Bibcode:1999A&A...341..121S
  4. Edwards, T. W. (April 1976), "MK classification for visual binary components", Astronomical Journal, 81: 245–249, Bibcode:1976AJ.....81..245E, doi:10.1086/111879
  5. Pourbaix, D.; et al. (September 2004), "SB9: The ninth catalogue of spectroscopic binary orbits", Astronomy and Astrophysics, 424: 727–732, arXiv:astro-ph/0406573, Bibcode:2004A&A...424..727P, doi:10.1051/0004-6361:20041213
  6. Mallik, Sushma V.; Parthasarathy, M.; Pati, A. K. (October 2003), "Lithium and rotation in F and G dwarfs and subgiants", Astronomy and Astrophysics, 409: 251–261, Bibcode:2003A&A...409..251M, doi:10.1051/0004-6361:20031084
  7. Rotanev Archived November 21, 2008, at the Wayback Machine, Stars, Jim Kaler. Accessed on line October 1, 2008.
  8. HD 196524 -- Spectroscopic binary, database entry, SIMBAD. Accessed on line October 1, 2008.
  9. Entry 20375+1436, The Washington Double Star Catalog Archived September 8, 2008, at the Wayback Machine, United States Naval Observatory. Accessed on line October 1, 2008.
  10. HR 7882, 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 1, 2008.
  11. Kunitzsch, Paul; Smart, Tim (2006). A Dictionary of Modern star Names: A Short Guide to 254 Star Names and Their Derivations (2nd rev. ed.). Cambridge, Massachusetts: Sky Pub. ISBN 978-1-931559-44-7.
  12. "Naming Stars". IAU.org. Retrieved 16 December 2017.
  13. 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:1012.0707 [astro-ph.SR].
  14. Webb, T.W. (1859). Celestial Objects for Common Telescopes. London: Longmans, Green and Co. pp. 193–194.
  15. 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.
  16. IAU Working Group on Star Names (WGSN), International Astronomical Union, retrieved 22 May 2016.
  17. "WG Triennial Report (2015-2018) - Star Names" (PDF). p. 5. Retrieved 2018-07-14.
  18. (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.
  19. Burnham, Robert (1978), Burnham's celestial handbook: an observer's guide to the universe beyond the Solar System, Dover Books on Astronomy, 2 (2nd ed.), Courier Dover Publications, p. 820, ISBN 0-486-23568-8
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