Alpha Crateris

Alpha Crateris
Location of α Crateris (circled)
Observation data
Epoch J2000      Equinox ICRS
Constellation Crater
Right ascension 10h 59m 46.46516s
Declination −18° 17′ 55.6304″
Apparent magnitude (V) 4.07
Characteristics
Evolutionary stage red clump
Spectral type K1 III
B−V color index 1.079±0.041
Astrometry
Radial velocity (Rv)47.54±0.16 km/s
Proper motion (μ) RA: −462.303 mas/yr
Dec.: 128.614 mas/yr
Parallax (π)20.3693±0.1704 mas
Distance160 ± 1 ly
(49.1 ± 0.4 pc)
Absolute magnitude (MV)+0.44
Details
Mass1.81 M☉
Radius12.32 R☉
Luminosity66.0 L☉
Surface gravity (log g)2.53 cgs
Temperature4.691 K
Metallicity [Fe/H]+0.01 dex
Age2.06 Gyr
Other designations
Alkes, Alpha Crt, α Crt, 7 Crt, BD−17°3273, FK5 1283, HD 95272, HIP 53740, HR 4287, SAO 156375, LTT 4040, NLTT 25942
Database references
SIMBADdata

Alpha Crateris is an orange-hued star in the southern constellation of Crater. It has the proper name Alkes, pronounced /ˈælkɛs/; Alpha Crateris is its Bayer designation. This is a cool giant star that is visible to the naked eye with an apparent visual magnitude of 4.07. Based on parallax measurements, it is located at a distance of approximately 160 light-years (49 pc) from the Earth. It is drifting further away with a line of sight velocity component of 47.5 km/s.

Nomenclature

α Crateris (Latinised to Alpha Crateris) is the star's Bayer designation, abbreviated Alpha Crt or α Crt.

It bore the traditional name Alkes, from the Arabic الكاس alkās or الكأس alka's "the cup". In the catalogue of stars in the Calendarium of Al Achsasi al Mouakket, this star was designated Aoul al Batjna (أول ألباطیة awwal al-bāṭiya), which was translated into Latin as Prima Crateris, meaning "first [star] of the Cup". In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalogue and standardize proper names for stars. The WGSN approved the name Alkes for this star on 12 September 2016 and it is now so included in the List of IAU-approved Star Names.

In Chinese, 翼宿 (Yì Sù), meaning Wings (asterism), refers to an asterism consisting of Alpha Crateris, Gamma Crateris, Zeta Crateris, Lambda Crateris, Nu Hydrae, Eta Crateris, Delta Crateris, Iota Crateris, Kappa Crateris, Epsilon Crateris, HD 95808, HD 93833, Theta Crateris, HD 102574, HD 100219, Beta Crateris, HD 99922, HD 100307, HD 96819, Chi1 Hydrae, HD 102620 and HD 103462. Consequently, Alpha Crateris itself is known as 翼宿一 (Yì Sù yī, English: the First Star of Wings).

Properties

Alpha Crateris is a giant star with a stellar classification of K1III, which suggests it has exhausted the supply of hydrogen at its core and evolved away from the main sequence. It is thought to be a horizontal branch star, meaning it is fusing helium in its core after a helium flash. Cool horizontal branch stars are often called red clump giants as they form a noticeable grouping near the hot edge of the red giant branch in the H–R diagrams of clusters with near-solar metallicity. On this basis it is calculated to have a mass of 1.81 M☉, a luminosity of 66 L☉, and an age around two billion years. Its effective temperature is 4691 K. Or it might be a red-giant branch star, still fusing hydrogen in a shell around an inert helium core, in which case it would be slightly less massive, older, cooler, larger, and more luminous.

Namesake

USS Alkes (AK-110) was a United States Navy Crater-class cargo ship named after the star.

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. 1 2 Ducati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237. Bibcode:2002yCat.2237....0D.
  4. ↑ Puzeras, E.; et al. (2010). "High-resolution spectroscopic study of red clump stars in the Galaxy: Iron-group elements". Monthly Notices of the Royal Astronomical Society. 408 (2): 1225. arXiv:1006.3857. Bibcode:2010MNRAS.408.1225P. doi:10.1111/j.1365-2966.2010.17195.x.
  5. ↑ Houk, N.; Smith-Moore, M. (1988). "Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4, Declinations -26°.0 to -12°.0". Michigan Catalogue of Two-dimensional Spectral Types for the HD Stars. Volume 4. Bibcode:1988mcts.book.....H.
  6. 1 2 Massarotti, Alessandro; et al. (2008). "Rotational and Radial Velocities for a Sample of 761 HIPPARCOS Giants and the Role of Bi narity". The Astronomical Journal. 135 (1): 209–231. Bibcode:2008AJ....135..209M. doi:10.1088/0004-6256/135/1/209.
  7. ↑ Cardini, D. (January 2005). "Mg II chromospheric radiative loss rates in cool active and quiet stars". Astronomy and Astrophysics. 430: 303–311. arXiv:astro-ph/0409683. Bibcode:2005A&A...430..303C. doi:10.1051/0004-6361:20041440. S2CID 12136256.
  8. 1 2 Reffert, Sabine; et al. (2015). "Precise radial velocities of giant stars. VII. Occurrence rate of giant extrasolar planets as a function of mass and metallicity". Astronomy & Astrophysics. 574: A116. arXiv:1412.4634. Bibcode:2015A&A...574A.116R. doi:10.1051/0004-6361/201322360. hdl:10722/215277. S2CID 59334290.
  9. ↑ "alf Crt". SIMBAD. Centre de données astronomiques de Strasbourg. Retrieved 2026-08-01.
  10. ↑ Davis, George A. (1944). "The pronunciations, derivations, and meanings of a selected list of star names". Popular Astronomy. 52: 8–30.
  11. 1 2 "Naming Stars". IAU.org. Archived from the original on 10 March 2025. Retrieved 16 December 2017.
  12. ↑ Knobel, E. B. (June 1895). "Al Achsasi Al Mouakket, on a catalogue of stars in the Calendarium of Mohammad Al Achsasi Al Mouakket". Monthly Notices of the Royal Astronomical Society. 55 (8): 429. Bibcode:1895MNRAS..55..429K. doi:10.1093/mnras/55.8.429.
  13. ↑ "IAU Working Group on Star Names (WGSN)". International Astronomical Union. Archived from the original on 10 June 2016. Retrieved 22 May 2016.
  14. ↑ (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.
  15. ↑ (in Chinese) 香港太空館 - 研究資源 - 亮星中英對照表 Archived 2008-10-25 at the Wayback Machine, Hong Kong Space Museum. Accessed on line November 23, 2010.