There is no official strategy with regards to how the stars of a particular constellation are to be connected to form a picture. Constellations are useful to modern astronomy because they allow an approximate location for knowing where objects in the sky can be found. The principal star, Alpha, is really a double star with its secondary component, Proxima, on the sunward side of its orbit. Therefore, technically, Proxima is the closest star to our sun. Its distance from the sun is about 4.3 light years or 25 trillion miles.
Combustion is a chemical process which releases energy.
The atoms which partake in the reaction are not changed in any way because of the reaction. In the sun, four hydrogen protons are fused into one helium nucleus. The process is more complicated then that, but the concept is valid. In the fusion of four hydrogen protons some mass is converted into energy as helium atoms are created. This is the mechanism which powers most of the stars that we see in the sky.