Beta Eridani

β Eridani

Location of β Eridani (circled)
Observation data Epoch J2000.0      Equinox J2000.0 (ICRS)
Constellation	Eridanus
Right ascension	05^h 07^m 50.98549^s[1]
Declination	−05° 05′ 11.2055″[1]
Apparent magnitude (V)	2.796[2]
Characteristics
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]
Astrometry
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)	36.2456 ± 0.3575 mas[6]
Distance	90.0 ± 0.9 ly (27.6 ± 0.3 pc)
Absolute magnitude (MV)	+0.59[7]
Details
Mass	2.0[8] M☉
Radius	2.4[8] R☉
Luminosity	25[8] L☉
Surface gravity (log g)	3.58[5] cgs
Temperature	8,360,[9] 8,104[5] K
Metallicity [Fe/H]	–0.4[10] dex
Rotational velocity (v sin i)	196[3] km/s
Other designations
Cursa/Kursa,[11] Dhalim,[12] 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.[13]
Database references
SIMBAD	data

Beta Eridani (β Eridani, abbreviated Beta Eri, β Eri), formally named Cursa /ˈkɜːrsə/,^[14] is the second-brightest star in the constellation of Eridanus, located in the northeast end of this constellation near the shared border with Orion. 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]

Nomenclature

β Eridani is the bright star towards the top (north). The brightest star, towards the lower left, is Rigel. In between is the reflection nebula IC 2118.

Beta Eridani is the star's Bayer designation. It has the traditional name Cursa^[4][9] derived from Al Kursiyy al Jauzah, "the Chair (or "Footstool") of the Central One". This is the name of the star association consisting of this star along with Lambda Eridani, Psi Eridani and Tau Orionis.^[12] According to a NASA catalogue of stars, Al Kursiyy al Jauzah was the title of three stars: β Eri is Cursa, Psi Eridani Al Kursiyy al Jauzah I, and Lambda Eridani Al Kursiyy al Jauzah II (excluding Tau Orionis).^[15] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)^[16] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016^[17] included a table of the first two batches of names approved by the WGSN; which included Cursa for this star.

In Chinese, 玉井 (Yù Jǐng), "the Jade Well", refers to an asterism consisting of β Eridani, λ Eridani, ψ Eridani and τ Orionis.^[18] Consequently, the Chinese name for β Eridani itself is "the third star of Jade Well" (玉井三 Yù Jǐng sān).^[19] In older texts, Yu Jing was also spelt Yuh Tsing.^[12]

Properties

β Eridani has a spectral type of A3 III,^[3] with the luminosity class III indicating that this is a giant star which 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.^[20] The projected rotational velocity is a rapid 196 km s⁻¹,^[3] compared to 2 km s⁻¹ along the Sun's equator.^[21] The star is known to vary in apparent visual magnitude, ranging between 2.72 and 2.80.^[22] A particularly strong flare-up was reported in 1985.^[9][23]

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 through 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°.^[24] It has the catalogue identifier CCDM J05079-0506B.^[25]

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, S2CID 18759600
2. Cousins, A. W. J. (1984), "Standardization of Broadband Photometry of Equatorial Standards", South African Astronomical Observatory Circulars, 8: 59, Bibcode:1984SAAOC...8...59C
3. 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 (3): 897–911, arXiv:astro-ph/0205255, Bibcode:2002A&A...393..897R, doi:10.1051/0004-6361:20020943, S2CID 14070763
4. 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. 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. Brown, A. G. A.; et al. (Gaia collaboration) (2021). "Gaia Early Data Release 3: Summary of the contents and survey properties". Astronomy & Astrophysics. 649: A1. arXiv:2012.01533. Bibcode:2021A&A...649A...1G. doi:10.1051/0004-6361/202039657. S2CID 227254300. (Erratum: doi:10.1051/0004-6361/202039657e). Gaia EDR3 record for this source at VizieR.
7. Anderson, E.; Francis, Ch. (2012), "XHIP: An extended hipparcos compilation", Astronomy Letters, 38 (5): 331, arXiv:1108.4971, Bibcode:2012AstL...38..331A, doi:10.1134/S1063773712050015, S2CID 119257644.
8. 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
9. Kaler, James B., "Cursa (Beta Eridani)", Stars, University of Illinois, retrieved 2012-01-10
10. Kamp, I.; Hempel, M.; Holweger, H. (June 2002), "Do dusty A stars exhibit accretion signatures in their photospheres?", Astronomy and Astrophysics, 388 (3): 978–984, arXiv:astro-ph/0204449, Bibcode:2002A&A...388..978K, doi:10.1051/0004-6361:20020493, S2CID 18191361
11. Moore, Patrick (2006), The amateur astronomer, Patrick Moore's Practical Astronomy Series (12th ed.), Birkhäuser, p. 200, ISBN 1-85233-878-4
12. 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
13. "bet Eri -- Variable Star", SIMBAD, Centre de Données astronomiques de Strasbourg, retrieved 2012-01-10
14. "IAU Catalog of Star Names". Retrieved 28 July 2016.
15. 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
16. "IAU Working Group on Star Names (WGSN)". Retrieved 22 May 2016.
17. "Bulletin of the IAU Working Group on Star Names, No. 1" (PDF). Retrieved 28 July 2016.
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. (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2009-09-29 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.
20. "The Colour of Stars", Australia Telescope, Outreach and Education, Commonwealth Scientific and Industrial Research Organisation, December 21, 2004, archived from the original on 2012-03-18, retrieved 2012-01-16
21. Unsöld, Albrecht; Baschek, B. (2001), The new cosmos: an introduction to astronomy and astrophysics (5th ed.), Springer, p. 167, Bibcode:2001ncia.book.....U, ISBN 3-540-67877-8
22. NSV 1841, database entry, New Catalogue of Suspected Variable Stars, the improved version, Sternberg Astronomical Institute, Moscow, Russia. Accessed on line September 17, 2008.
23. Brunner, B. H. (June 1985), "A Flare of Beta-Eridani", Sky and Telescope, 69 (6): 484, Bibcode:1985S&T....69R.484B
24. 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, vol. 1, Bibcode:2011yCat....102026M
25. BD-05 1162B -- Star in double system, database entry, SIMBAD. Accessed on line September 17, 2008.