Starfield. View of a starfield over silhouetted trees. The constellation of Orion can be seen at right. Orion is one of the most prominent constellations, and contains the striking group known as Orion's belt, made up of three equally bright stars equally spaced (centre right). Below the belt, just above the trees is the star Rigel (Beta orionis). The star Betelgeuse (Alpha orionis) appears above the belt. At lower left is the star Sirius (Alpha Canis Majoris). This is the brightest star in the sky (excluding the Sun), and is also known as the Dog Star.