Beta Cancri

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β Cancri
Cancer constellation map.png
β Cancri is the bottom right star in the "crab"
Observation data
Epoch J2000      Equinox J2000
Constellation Cancer
Right ascension 08h 16m 30.9206s[1]
Declination +09° 11′ 07.961″[1]
Apparent magnitude (V) 3.50 - 3.58[2]
Spectral type K4III Ba1[3]
U−B color index +1.77[4]
B−V color index +1.48[4]
Radial velocity (Rv) 22.94[5] km/s
Proper motion (μ) RA: −46.80[1] mas/yr
Dec.: −48.65[1] mas/yr
Parallax (π) 11.23 ± 0.97[1] mas
Distance 290 ± 30 ly
(89 ± 8 pc)
Absolute magnitude (MV) −1.218[6]
Radius 61[7] R
Luminosity 871[7] L
Surface gravity (log g) 1.5[7] cgs
Temperature 3,990[7] K
Metallicity −0.24[7]
Rotational velocity (v sin i) 6.9[7] km/s
Other designations
β Cancri, Al Tarf, 17 Cancri, HR 3249, HD 69267, BD+09°1917, FK5 312, HIP 40526, SAO 116569, GC 11254, ADS 6704, CCDM 08165+0911
Database references

β Cancri (Beta Cancri, Al Tarf) is the brightest star in the zodiacal constellation Cancer. At approximately 290 light years from earth, it has a visual apparent magnitude of +3.5 and absolute magnitude of −1.2. The star is an orange K-type giant, about 61 times the radius of the Sun.

The traditional name Al Tarf (anglicized as Altarf[8]), can be translated from Arabic as "end" or "edge".[9]

β Cancri is Barium star, a type of cool giant showing enhanced abundances of Barium.[10] It is also suspected to vary slightly in brightness.[2]

β Cancri is known to have a fourteenth magnitude, red dwarf companion star. From its angular distance of 29 arcseconds, the companion's distance from its parent star is estimated at some 2600 AU, and has an orbital period of 76,000 years.[9]

In a paper published in the journal Astronomy & Astrophysics on May 12, 2014, evidence was presented of a planet orbiting β Cancri. Using radial velocity data from repeated observations of the star, the planet is estimated to have a minimum mass of approximately 7.8 times that of Jupiter, and an orbit of 605 days.[11]

The Beta Cancri planetary system[12]
(in order from star)
Mass Semimajor axis
Orbital period
Eccentricity Inclination Radius
b 7.8 ± 0.8 MJ 1.7 ± 0.1 605.2 ± 4.0 0.08 ± 0.02


  1. ^ a b c d e Van Leeuwen, F. (2007). "Validation of the new Hipparcos reduction". Astronomy and Astrophysics. 474 (2): 653. Bibcode:2007A&A...474..653V. arXiv:0708.1752Freely accessible. doi:10.1051/0004-6361:20078357. 
  2. ^ a b Samus, N. N.; Durlevich, O. V.; et al. (2009). "VizieR Online Data Catalog: General Catalogue of Variable Stars (Samus+ 2007-2013)". VizieR On-line Data Catalog: B/gcvs. Originally published in: 2009yCat....102025S. 1. Bibcode:2009yCat....102025S. 
  3. ^ Lu, Phillip K. (1991). "Taxonomy of barium stars". Astronomical Journal (ISSN 0004-6256). 101: 2229. Bibcode:1991AJ....101.2229L. doi:10.1086/115845. 
  4. ^ a b Mermilliod, J.-C. (1986). "Compilation of Eggen's UBV data, transformed to UBV (unpublished)". Catalogue of Eggen's UBV data. Bibcode:1986EgUBV........0M. 
  5. ^ Famaey, B.; Jorissen, A.; Luri, X.; Mayor, M.; Udry, S.; Dejonghe, H.; Turon, C. (2005). "Local kinematics of K and M giants from CORAVEL/Hipparcos/Tycho-2 data. Revisiting the concept of superclusters". Astronomy and Astrophysics. 430: 165. Bibcode:2005A&A...430..165F. arXiv:astro-ph/0409579Freely accessible. doi:10.1051/0004-6361:20041272. 
  6. ^ Cassatella, A.; Altamore, A.; Badiali, M.; Cardini, D. (2001). "On the Wilson-Bappu relationship in the Mg II k line". Astronomy and Astrophysics. 374 (3): 1085. Bibcode:2001A&A...374.1085C. arXiv:astro-ph/0106070Freely accessible. doi:10.1051/0004-6361:20010816. 
  7. ^ a b c d e f Massarotti, Alessandro; Latham, David W.; Stefanik, Robert P.; Fogel, Jeffrey (2008). "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Binarity". The Astronomical Journal. 135: 209. Bibcode:2008AJ....135..209M. doi:10.1088/0004-6256/135/1/209. 
  8. ^ Hoffleit, D.; Warren, W. H. (1995). "VizieR Online Data Catalog: Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)". VizieR On-line Data Catalog: V/50. Originally published in: 1964BS....C......0H. 5050. Bibcode:1995yCat.5050....0H. 
  9. ^ a b Kaler, James B. "AL TARF (Beta Cancri)". Stars. University of Illinois. Retrieved 2010-02-23. 
  10. ^ Gomez, A. E.; Luri, X.; Grenier, S.; Prevot, L.; Mennessier, M. O.; Figueras, F.; Torra, J. (1997). "Absolute magnitudes and kinematics of barium stars". Astronomy and Astrophysics. 319: 881. Bibcode:1997A&A...319..881G. 
  11. ^ Lee, B.-C.; Han, I.; Park, M.-G.; Mkrtichian, D. E.; Hatzes, A. P.; Kim, K.-M. (2014). "Planetary companions in K giants β Cancri, μ Leonis, and β Ursae Minoris". Astronomy & Astrophysics. 566: A67. Bibcode:2014A&A...566A..67L. arXiv:1405.2127Freely accessible. doi:10.1051/0004-6361/201322608. 
  12. ^ "Notes on beta Cnc b". Extrasolar Planets Encyclopaedia. Retrieved 28 February 2017.