PIX4593026: Winter hexagon and March - Winter hexagon - The winter hexagon is an asterism formed by the stars Sirius, Procyon, Pollux, Capella, Aldebaran and Rigel. The image also shows the planet Mars (the brightest spot) and the comet Holmes (scattered spot on the right. 19 December 2007. Winter hexagon is composed by bright stars Sirius, Procyon, Pollux, Capella, Aldebaran and Rigel. The image shows also the comet 17P/Holmes. But very prominent inside the Hexagon is Mars. December 19, 2007 / Bridgeman Images