Alpha Cancri

α Cancri
α Cancri, circled, is the bottom left star in the "crab".
Observation data
Epoch J2000      Equinox ICRS
Constellation Cancer
Right ascension 08h 58m 29.2042s
Declination +11° 51′ 27.649″
Apparent magnitude (V) 4.20 to 4.27
Characteristics
Spectral type kA7VmF0/2III/IVSr
U−B color index +0.15
B−V color index +0.14
R−I color index +0.04
Astrometry
Radial velocity (Rv)−12.1±0.8 km/s
Proper motion (μ) RA: 42.181 mas/yr
Dec.: −31.160 mas/yr
Parallax (π)18.3304±0.3216 mas
Distance178 ± 3 ly
(54.6 ± 1.0 pc)
Absolute magnitude (MV)0.46
Details
A
Mass2.10 M☉
Radius3.655 R☉
Luminosity49 L☉
Surface gravity (log g)3.73 cgs
Temperature7,943 K
Rotational velocity (v sin i)75 km/s
B
Mass0.38 M☉
Radius0.67 R☉
Luminosity0.13 L☉
Surface gravity (log g)4.61 cgs
Temperature4,205 K
Other designations
Acubens, Sertan, Sartan, α Cnc, Alpha Cancri, Alpha Cnc, 65 Cancri, 65 Cnc, BD+12 1948, FK5 337, GC 12406, HD 76756, HIP 44066, HR 3572, SAO 98267, PPM 125972, ADS 7115 A, CCDM J08585+1151A
Database references
SIMBADdata
B

Alpha Cancri is a star system in the northern constellation of Cancer. Its name is a Bayer designation that is Latinized from α Cancri, and abbreviated Alpha Cnc or α Cnc. The primary component has the proper name Acubens, pronounced /ˈækjuːbɛnz/. It forms a fourth-magnitude star with an apparent magnitude of 4.20, making it visible to the naked eye under good viewing conditions. Based on parallax measurements, it is located at a distance of 178 light-years (55 pc) from the Sun, but is drifting closer with a radial velocity of −12 km/s. Since it is near the ecliptic, it can be occulted by the Moon.

Properties

The primary component, α Cancri A, has a stellar classification of kA7VmF0/2III/IVSr, indicating an Am star with calcium K-lines similar to an A7 main sequence star and hydrogen lines more like an F0 giant or subgiant star. It is a white A-type main-sequence star with an apparent magnitude of +4.26. The star has 2.10 times the mass of the Sun and 3.7 times the Sun's radius. It has a high rate of spin, showing a projected rotational velocity of 75 km/s. The star is radiating 49 times the luminosity of the Sun from its photosphere at an effective temperature of 7,943 K.

Its companion, α Cancri B, is an eleventh-magnitude star. In the year 1836, its position angle was observed at 325 degrees with a separation from the main star α Cancri A of 11.3 arcseconds. α Cancri A may itself be a close binary, consisting of two stars with similar brightness and a separation of 0.1 arcsecond, though this is questioned. Indeed, a light curve generated during a 2014 lunar occultation failed to demonstrate a close companion.

Nomenclature

α Cancri (Latinised to Alpha Cancri) is the star's Bayer designation.

Johann Bode designated this star as α2 Cancri, as he also used the superscript α1 for the star 60 Cancri. Bode's superscripts are rarely used though, so the designations have reverted ever since.

The traditional name Acubens (Açubens) is derived from the Arabic الزبانى al zubanāh, 'the claws'. A second name, Sertan /ˈsɜːrtæn/, derives from the Arabic al-saraṭān, 'the crab'. These names were traditionally shared with ι Cancri, which marks the crab's other claw. The International Astronomical Union's Working Group on Star Names (WGSN) chose Acubens as the proper name for the primary component α Cancri A.

In modern culture

USS Acubens (AKS-5) was a United States Navy ship.

References

  1. 1 2 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. XHIP record for this object at VizieR.
  2. 1 2 3 4 5 Vallenari, A.; et al. (Gaia collaboration) (2023). "Gaia Data Release 3. Summary of the content and survey properties". Astronomy and Astrophysics. 674: A1. arXiv:2208.00211. Bibcode:2023A&A...674A...1G. doi:10.1051/0004-6361/202243940. S2CID 244398875. Gaia DR3 record for this source at VizieR.
  3. ↑ "NSV 4327, database entry". New Catalogue of Suspected Variable Stars, the improved version. Moscow, Russia: Sternberg Astronomical Institute. Retrieved October 20, 2009.
  4. ↑ Sreedhar Rao, S.; Abhyankar, K. D. (1991). "MK morphological study of AM stars at 66 A/Mm". Journal of Astrophysics and Astronomy. 12 (2): 133. Bibcode:1991JApA...12..133S. doi:10.1007/BF02709302. S2CID 59324843.
  5. 1 2 3 4 5 Hoffleit, D.; Warren, Jr., W. H. "HR 3572, database entry". The Bright Star Catalogue (5th Revised (Preliminary Version) ed.). Centre de Données astronomiques de Strasbourg. V/50. Retrieved October 20, 2009.
  6. 1 2 Gontcharov, G. A. (2006). "Pulkovo Compilation of Radial Velocities for 35 495 Hipparcos stars in a common system". Astronomy Letters. 32 (11): 759–771. arXiv:1606.08053. Bibcode:2006AstL...32..759G. doi:10.1134/S1063773706110065. S2CID 119231169.
  7. 1 2 3 Tokovinin, A. A. (1997). "MSC - a catalogue of physical multiple stars". Astronomy and Astrophysics Supplement Series. 124: 75–84. Bibcode:1997A&AS..124...75T. doi:10.1051/aas:1997181.
  8. 1 2 3 McDonald, I.; et al. (October 2017). "Fundamental parameters and infrared excesses of Tycho-Gaia stars". Monthly Notices of the Royal Astronomical Society. 471 (1): 770–791. arXiv:1706.02208. Bibcode:2017MNRAS.471..770M. doi:10.1093/mnras/stx1433. ISSN 0035-8711. Acubens' database entry at VizieR.
  9. 1 2 3 Baines, Ellyn K.; et al. (2018). "Fundamental Parameters of 87 Stars from the Navy Precision Optical Interferometer". The Astronomical Journal. 155 (1): 30. arXiv:1712.08109. Bibcode:2018AJ....155...30B. doi:10.3847/1538-3881/aa9d8b. S2CID 119427037.
  10. 1 2 Royer, F.; et al. (2002). "Rotational velocities of A-type stars in the northern hemisphere. II. Measurement of v sin i in the northern hemisphere". Astronomy and Astrophysics. 393 (3): 897–911. arXiv:astro-ph/0205255. Bibcode:2002A&A...393..897R. doi:10.1051/0004-6361:20020943. S2CID 14070763.
  11. 1 2 3 4 Stassun, Keivan G.; Oelkers, Ryan J.; Paegert, Martin; et al. (2019-10-01). "The Revised TESS Input Catalog and Candidate Target List". The Astronomical Journal. 158 (4): 138. arXiv:1905.10694. Bibcode:2019AJ....158..138S. doi:10.3847/1538-3881/ab3467. ISSN 0004-6256.
  12. ↑ "alf Cnc". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2009-09-20.
  13. ↑ 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 Publishing. ISBN 978-1-931559-44-7.
  14. 1 2 Richichi, A.; et al. (November 2014). "First Lunar Occultation Results from the 2.4 m Thai National Telescope Equipped with ULTRASPEC". The Astronomical Journal. 148 (5): 100. arXiv:1408.0073. Bibcode:2014AJ....148..100R. doi:10.1088/0004-6256/148/5/100. 100.
  15. ↑ "CCDM (Catalog of Components of Double & Multiple stars (Dommanget+ 2002)". VizieR. Centre de Données astronomiques de Strasbourg. Retrieved 2010-05-13.
  16. ↑ "Acubens". Alcyone Bright Star Catalogue. Retrieved 2010-05-13.
  17. ↑ Bode, Johann Elert (1801). Uranographia. Berlin. p. 49. doi:10.3931/e-rara-11148.
  18. ↑ Allen, Richard Hinckley (1963). "Star Names — Their Lore and Meaning: Cancer" (Dover ed.). Retrieved 2025-05-18.
  19. ↑ "IAU Catalog of Star Names". International Astronomical Union. Retrieved 2026-01-02.