Gacrux
Gacrux , Gamma Crucis (Latinised from γ Crucis, abbreviated Gamma Cru, γ Cru), is the nearest class M giant star to the Sun. With an apparent visual magnitude of +1.63, it is the third-brightest star (hence its name) in the southern constellation of Crux (the Southern Cross) and is listed 26th of the brightest stars in the night sky. A line from the two "Pointers", Alpha Centauri through Beta Centauri, leads to within 1° north of this star. Distance has been determined using parallax measurements made during the Hipparcos mission, yielding from the Sun. Nomenclature. "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. The historical name "Gacrux" was coined by astronomer Elijah Hinsdale Burritt (1794-1838). In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN's first  bulletin of July 2016 included a table of the first two batches of names approved by the WGSN; which included "Gacrux" for this star. In Chinese astronomy, Gamma Crucis was known as (, .). The people of Aranda and Luritja tribe around Hermannsburg, Central Australia named "Iritjinga", "The Eagle-hawk", a quadrangular arrangement comprising Gacrux, Delta Crucis (Imai), Gamma Centauri (Muhilfain) and Delta Centauri (Ma Wei). Among Portuguese-speaking peoples, especially in Brazil, it is also named "Rubídea" (or Ruby-like), in reference to its colour. Physical properties. Gacrux has the MK system stellar classification of M3.5 III. It has evolved off  of the main sequence to become a red giant star, but is most likely on the red giant branch rather than the asymptotic giant branch. Although only 30% more massive than the Sun, at this stage the star has expanded to 120 times the Sun's radius. It is radiating roughly 760 times the luminosity of the Sun from its expanded outer envelope. With an effective temperature of 3,689 K, the colour of Gacrux is a prominent reddish-orange, well in keeping with its spectral classification. It is a semi-regular variable with multiple periods. (See table at left.) 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. 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, which is about 400 light years distant from Earth. In culture. Gacrux is represented in the flags of Australia, New Zealand, Samoa and Papua New Guinea as  one of five stars which comprise the Southern Cross. 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. 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.