The three bright stars that make up the well known asterism, Orion's belt, are Alnitak, Alnilam and Mintaka. Astronomically speaking, all three of these stars are great distances apart from each other in space.Unfortunately, I'm not so sure in numbers how far each star is apart. I can tell you though the distance of Alnitak from Sol (The Sun) is about 795 light years away. I'm not too dubious about the other two stars. And Sirius is not associated with the Orion constellation. It is associated with the constellation Canis Major. In latin meaning the great or big dog. This constellation can be found a few degrees to the far bottom left below the Orion constellation.