Wikipedia
Alnitak
Alnitak, designated Zeta Orionis (ζ Orionis, abbreviated Zeta Ori, ζ Ori) and 50 Orionis (50 Ori), is a multiple star several hundred parsecs from the Sun in the constellation of Orion. It is part of Orion's Belt along with Alnilam and Mintaka.
The primary star is a hot blue supergiant with an absolute magnitude of -6.0 and is the brightest class O star in the night sky with a visual magnitude of +2.0. It has two bluish 4th magnitude companions, one finely resolved and one only detected interferometrically and spectroscopically, producing a combined magnitude for the trio of +1.77. The stars are members of the Orion OB1 association and the Collinder 70 association.