The brightest star in a constellation is often referred to as the alpha star. Alpha stars are usually the brightest and most prominent stars in a constellation, and they are usually given the Greek letter 'alpha' as part of their name. In the case of the constellation Orion, the brightest star is Alpha Orionis, also known as Betelgeuse. Similarly, the brightest star in the constellation Ursa Major is Alpha Ursae Majoris, also known as Dubhe. The second brightest star in a constellation is usually referred to as the beta star, and the third brightest is referred to as the gamma star. The fourth brightest star in a constellation is referred to as the zeta star, and in the case of the constellation Orion, this is Zeta Orionis, also known as Alnitak. Finally, the sixth brightest star in a constellation is referred to as the lucida star, and in the case of the constellation Orion, this is Lucida Orionis, also known as Rigel.