Beta Eridani

From Wikipedia, the free encyclopedia
Jump to: navigation, search
β Eridani
Eridanus constellation map.svg
Red circle.svg

Location of β Eridani (circled)
Observation data
Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation Eridanus
Right ascension 05h 07m 50.98549s[1]
Declination −05° 05′ 11.2055″[1]
Apparent magnitude (V) 2.796[2]
Spectral type A3 III var[3]
U−B color index +0.124[2]
B−V color index +0.110[2]
R−I color index +0.08[4]
Radial velocity (Rv) –3.6[5] km/s
Proper motion (μ) RA: -82.82[1] mas/yr
Dec.: -75.39[1] mas/yr
Parallax (π) 36.50 ± 0.42[1] mas
Distance 89 ± 1 ly
(27.4 ± 0.3 pc)
Mass 2.0[6] M
Radius 2.4[6] R
Luminosity 25[6] L
Surface gravity (log g) 3.58[5] cgs
Temperature 8,360,[7] 8,104[5] K
Metallicity [Fe/H] –0.4[8] dex
Rotational velocity (v sin i) 196[3] km/s
Other designations
Cursa/Kursa,[9] Dhalim,[10] β Eri, Beta Eridani, Beta Eri, 67 Eridani, 67 Eri, BD−05 1162, CCDM J05079-0506A, FK5 188, GC 6274, GJ 9175, HD 33111, HIP 23875, HR 1666, IDS 05030-0513 A, PPM 187729, SAO 131794, WDS 05078-0505A.[11]

Beta Eridani (Beta Eri, β Eridani, β Eri) is the second brightest star in the constellation of Eridanus, located in the northeast end of this constellation near the shared border with Orion. It has the traditional name Cursa.[4][7] The apparent visual magnitude of this star is 2.796,[2] so it can be viewed with the naked eye in dark skies. Parallax measurements yield an estimated distance of about 89 light-years (27 parsecs) from the Earth.[1]


β Eridani has a spectral type of A3 III,[3] with the III luminosity class indicating this is a giant star that has consumed the hydrogen at its core and evolved away from the main sequence. The effective temperature of the outer envelope is about 8,104 K,[5] which gives the star a white hue typical of A-type stars.[12] The projected rotational velocity is a rapid 196 km s−1,[3] compared to 2 km s−1 along the Sun's equator.[13] The star is known to vary in apparent visual magnitude, ranging between 2.72 and 2.80.[14] A particularly strong flare up was reported in 1985.[7][15]

The location and trajectory of this star suggest that it is a member of the Ursa Major supergroup, an association of stars that share a common origin and motion though space. However, its photometric properties indicate that it may instead be an interloper.[5] Beta Eridani has an optical companion star with an apparent magnitude 10.90 at an angular separation of 120 arcseconds and a position angle of 148°.[16] It has the catalogue identifier CCDM J05079-0506B.[17]


The term Cursa is derived from Al Kursiyy al Jauzah, "the Chair (or "Footstool") of the Central One". This is the name of star association consisting this star, along with λ Eri, ψ Eri and τ Ori.[10] According a NASA catalogue of stars, Al Kursiyy al Jauzah was the title of three stars: β Eri is Cursa, ψ Eridani Al Kursiyy al Jauzah I, and λ Eridani Al Kursiyy al Jauzah II (excluding τ Orionis).[18]

In Chinese, 玉井 (Yù Jǐng), "the Jade Well", refers to an asterism consisting of β Eridani, λ Eridani, ψ Eridani and τ Orionis.[19] Consequently, β Eridani itself is known as "the third star of Jade Well" (玉井三 Yù Jǐng sān).[20] In older texts, Yu Jing was also spelt Yuh Tsing.[10]

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 Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars 8: 59, Bibcode:1984SAAOC...8...59C 
  3. ^ a b c d Royer, F.; et al. (October 2002), "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i", Astronomy and Astrophysics 393: 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943 
  4. ^ a b HR 1666, 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 September 17, 2008.
  5. ^ a b c d e King, Jeremy R.; et al. (April 2003), "Stellar Kinematic Groups. II. A Reexamination of the Membership, Activity, and Age of the Ursa Major Group", The Astronomical Journal 125 (4): 1980–2017, Bibcode:2003AJ....125.1980K, doi:10.1086/368241 
  6. ^ a b c Malagnini, M. L.; Morossi, C. (November 1990), "Accurate absolute luminosities, effective temperatures, radii, masses and surface gravities for a selected sample of field stars", Astronomy and Astrophysics Supplement Series 85 (3): 1015–1019, Bibcode:1990A&AS...85.1015M 
  7. ^ a b c Kaler, James B., "Cursa (Beta Eridani)", Stars (University of Illinois), retrieved 2012-01-10 
  8. ^ Kamp, I.; Hempel, M.; Holweger, H. (June 2002), "Do dusty A stars exhibit accretion signatures in their photospheres?", Astronomy and Astrophysics 388: 978–984, arXiv:astro-ph/0204449, Bibcode:2002A&A...388..978K, doi:10.1051/0004-6361:20020493 
  9. ^ Moore, Patrick (2006), The amateur astronomer, Patrick Moore's Practical Astronomy Series (12th ed.), Birkhäuser, p. 200, ISBN 1-85233-878-4 
  10. ^ a b c Allen, R. H. (1963), Star Names: Their Lore and Meaning (Reprint ed.), New York, NY: Dover Publications Inc, p. 218, ISBN 0-486-21079-0, retrieved 2010-12-12 
  11. ^ "bet Eri -- Variable Star", SIMBAD (Centre de Données astronomiques de Strasbourg), retrieved 2012-01-10 
  12. ^ "The Colour of Stars", Australia Telescope, Outreach and Education (Commonwealth Scientific and Industrial Research Organisation), December 21, 2004, retrieved 2012-01-16 
  13. ^ Unsöld, Albrecht; Baschek, B. (2001), The new cosmos: an introduction to astronomy and astrophysics (5th ed.), Springer, p. 167, ISBN 3-540-67877-8 
  14. ^ NSV 1841, database entry, New Catalogue of Suspected Variable Stars, the improved version, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line September 17, 2008.
  15. ^ Brunner, B. H. (June 1985), "A Flare of Beta-Eridani", Sky and Telescope 69 (6): 484, Bibcode:1985S&T....69R.484B 
  16. ^ Mason, B. D.; Wycoff, G. L.; Hartkopf, W. I.; Douglass, G. G.; Worley, C. E. (November 2011), "The Washington Visual Double Star Catalog (Mason+ 2001-2011)", VizieR On-line Data Catalog: B/wds. Originally published in: 2001AJ....122.3466M, Bibcode:2011yCat....102026M 
  17. ^ BD-05 1162B -- Star in double system, database entry, SIMBAD. Accessed on line September 17, 2008.
  18. ^ Jack W. Rhoads - Technical Memorandum 33-507-A Reduced Star Catalog Containing 537 Named Stars, Jet Propulsion Laboratory, California Institute of Technology; November 15, 1971
  19. ^ (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. ^ (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.