Beta Centauri

Beta Centauri is a triple star system in the southern constellation of Centaurus. It is officially called Hadar (/ˈheɪdɑːr/). The Bayer designation of Beta Centauri is Latinised from β Centauri, and abbreviated Beta Cen or β Cen. The system's combined apparent visual magnitude of 0.61 makes it the second-brightest object in Centaurus and the eleventh brightest star in the night sky. According to dynamical parallax measurements, the distance to this system is about 361 light-years (111 parsecs).

β Centauri (Latinised to Beta Centauri) is the star system's Bayer designation.

It bore the traditional names Hadar and Agena. Hadar comes from the Arabic حضار (the root's meaning is "to be present" or "on the ground" or "settled, civilized area"), while the name Agena /əˈdʒiːnə/ is thought to be derived from the Latin genua, meaning "knees", from the star's position on the left knee of the centaur depicted in the constellation Centaurus. In 2016, the International Astronomical Union organized a Working Group on Star Names (WGSN) to catalog and standardize proper names for stars. The WGSN approved the name Hadar for the star β Centauri Aa on 21 August 2016 and it is now so entered in the IAU Catalog of Star Names.

The Chinese name for the star is 马腹一 (Mandarin: mǎ fù yī, "the First Star of the Horse's Abdomen").

The Boorong people indigenous to what is now northwestern Victoria, Australia named it Bermbermgle (together with α Centauri), two brothers who were noted for their courage and destructiveness, and who spear and kill Tchingal, "The Emu" (Coalsack Nebula). The Wotjobaluk people name the two brothers Bram-bram-bult.

The Mursi people of Ethiopia call this star Waar; it forms an asterism with δ Crucis (Imai), β Crucis (Thaadoi), and α Centauri (Sholbi).

Beta Centauri is one of the brightest stars in the sky at magnitude 0.61. Its brightness varies by a few hundredths of a magnitude, too small to be noticeable to the naked eye. Because of its spectral type and the detection of pulsations, the Aa component has been classified as a β Cephei variable.

Beta Centauri is well known in the Southern Hemisphere as the inner of the two "Pointers" to the constellation Crux, popularly known as the Southern Cross. A line made from the other pointer, Alpha Centauri, through Beta Centauri leads to within a few degrees of Gacrux, the star at the north end of the cross. Using Gacrux, a navigator can draw a line with Acrux at the south end to effectively determine south.