1. step 1 nebular cloud of gas and dust. 2. step 2 3. step 3 4. step 4 other gas and matter of the nebular cloud begin to rotate around the protostar, forming a flattened, disk. nuclear energy runs out; death, possible supernova condensed material begins to combine and form a core center. as it warms, a protostar is formed. cloud collapses under the force of its own gravitational attraction, usually triggered by a supernova stellar core heats as it grows: nuclear fusion begins and a star is born. 5. step 5 6. step 6