Arcturus ( /ɑrkˈtjʊərəs/; α Boo, α Boötis, Alpha Boötis) is the brightest star in the constellation Boötes and the northern celestial hemisphere. With a visual magnitude of −0.04, it is the fourth brightest star in the night sky, after −1.46 magnitude Sirius, −0.86 magnitude Canopus, and −0.27 magnitude Alpha Centauri. It is a relatively close star at only 36.7 light-years from Earth, and, together with Vega and Sirius, one of the most luminous stars in the Sun's neighborhood.
A type K1.5 IIIpe orange giant star, with an absolute magnitude of -0.30. It has likely exhausted its hydrogen and has begun fusing helium into oxygen and carbon in its core. It will continue to expand before sloughing off its outer shell and ending its life as a white dwarf inside a planetary nebula.
Read more about Arcturus: Observational History, Visibility, Physical Properties, Possible Planetary System, Names and Cultural Significance