γ Crucis (Latinised to Gamma Crucis) is the star's Bayer designation. Since Gacrux is at roughly −60° declination. It was known to the ancient Greeks and Romans, but oddly in the era lacked a traditional name, and was visible north of 40° latitude due to the precession of equinoxes. The astronomer Ptolemy counted it as part of the constellation of Centaurus.[12] The historical name Gacrux was coined by astronomer Elijah Hinsdale Burritt (1794-1838).[13][14] In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN)[15] to catalog and standardize proper names for stars. The WGSN's first bulletin of July 2016[16] included a table of the first two batches of names approved by the WGSN; which included Gacrux for this star.
InChinese astronomy, Gamma Crucis was known as 十字架一 (Shí Zì Jià yī, English: the First Star of Cross.).[17]
The atmosphere of this star is enriched with barium, which is usually explained by the transfer of material from a more evolved companion. Typically this companion will subsequently become a white dwarf.[20] However, no such companion has yet been detected. A +6.4 magnitude companion star lies about 2 arcminutes away at a position angle of 128° from the main star, and can be observed with binoculars. But it is only an optical companion,[21] which is about 400 light years distant from Earth.
It is also featured on the Republican flag of Brazil, along with 26 other stars, each of which represents a state. Gacrux represents the State of Bahia.[22] The position of the line passing through Gacrux and Acrux marks the local meridian of the sky observed from Rio de Janeiro, at 8:30 am. on 15 November 1889: the time when the republic was formally ratified.[23]
^ abcDucati, J. R. (2002). "VizieR Online Data Catalog: Catalogue of Stellar Photometry in Johnson's 11-color system". CDS/ADC Collection of Electronic Catalogues. 2237: 0. Bibcode:2002yCat.2237....0D.
^Wielen, R.; et al. (1999), "Sixth Catalogue of Fundamental Stars (FK6). Part I. Basic fundamental stars with direct solutions", Veröff. Astron. Rechen-Inst. Heidelb, 35 (35), Astronomisches Rechen-Institut Heidelberg: 1, Bibcode:1999VeARI..35....1W
^Elgarøy, Øystein; Engvold, Oddbjørn; Lund, Niels (March 1999), "The Wilson-Bappu effect of the MgII K line - dependence on stellar temperature, activity and metallicity", Astronomy and Astrophysics, 343: 222–228, Bibcode:1999A&A...343..222E
^ abMurdoch, Kaylene; Clark, M.; Hearnshaw, J. B. (January 1992), "The radial-velocity variability of Gamma Crucis", Monthly Notices of the Royal Astronomical Society, 254: 27–29, Bibcode:1992MNRAS.254...27M, doi:10.1093/mnras/254.1.27
^Johnson, H. L.; et al. (1966). "UBVRIJKL photometry of the bright stars". Communications of the Lunar and Planetary Laboratory. 4 (99): 99. Bibcode:1966CoLPL...4...99J.
^Richard Hinckley Allen, "Star Names: Their Lore and Meaning", Dover Press, 1963.
^Gomez, A. E.; Luri, X.; Grenier, S.; et al. (March 1997), "Absolute magnitudes and kinematics of barium stars", Astronomy and Astrophysics, 319: 881–885, Bibcode:1997A&A...319..881G