Arcturus (α Bottis)

 Arcturus (α Boötis) is the brightest star in the northern celestial hemisphere.  With a visual magnitude of −0.05, it is the fourth brightest star in the night sky, after −1.46 of Sirius magnitude, −0.86 of Canopus magnitude, and −0.27 of Alpha Centauri magnitude.  It is only 36.7 light years from Earth.

  Arcturus is a red giant star of type K0 III, about 110 times brighter than the Sun in visible light.  The Hipparcos satellite has suggested that Arcturus is a binary star, with the companion about twenty times weaker than the primary and orbiting close enough to be at the limit of our current ability to decipher it.

  Other designations:

  Alramech, Abramech, α Boötis, 16 Boötes, BD + 19° 2777, GCTP 3242.00, GJ 541, HD 124897, HIP 69673, HR 5340, LHS 48, SAO 100944.

 Credit: Giuseppe J Donatiello