Beta Delphini

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Beta Delphini
Diagram showing star positions and boundaries of the Delphinus constellation and its surroundings
Cercle rouge 100%.svg

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]
Spectral type F5 III + F5 IV[4]
B−V color index A: 0.43 ± 0.14
B: 0.56 ± 0.25[1]
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
Distance 101 ± 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]
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)
Semi-amplitude (K1)
7.6[5] km/s
Beta Delphini A
Mass 1.75 ± 0.002[2] M
Luminosity 24[6] L
Surface gravity (log g) 3.50[6] cgs
Temperature 6,587[6] K
Metallicity [Fe/H] –0.05[2] dex
Rotational velocity (v sin i) 49.8[6] km/s
Age 1.79+0.17
[2] Gyr
Beta Delphini B
Mass 1.47 ± 0.04[2] M
Luminosity 8[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]

Beta Delphini (Beta Del, β Delphini, β Del) is a binary star in the constellation of Delphinus. As a practical joke, the astronomer Niccolò Cacciatore gave it the name Rotanev, which is a reversal of his Latinized family name, Venator.[10] The name first appeared in Giuseppe Piazzi's Palermo Catalogue, published in 1814. Beta Delphini was found to be a binary star system in 1873 by the American astronomer S. W. Burnham.[11]

In Chinese, 瓠瓜 (Hù Guā), meaning Good Gourd, refers to an asterism consisting of β Delphini, α Delphini, γ2 Delphini, δ Delphini, and ζ Delphini.[12] Consequently, β Delphini itself is known as 瓠瓜二 (Hù Guā-er, English: the Second Star of Good Gourd.).[13]

This system consists of a pair of F-type stars 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]

See also[edit]


  1. ^ a b c d e f 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. ^ a b c d e f g h i j 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. ^ a b 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. ^ a b c d e 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. ^ a b Rotanev, 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, United States Naval Observatory. Accessed on line October 1, 2008.
  10. ^ a b 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. ^ 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 
  12. ^ (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.
  13. ^ (Chinese) 香港太空館 - 研究資源 - 亮星中英對照表, Hong Kong Space Museum. Accessed on line November 23, 2010.

External links[edit]