 The final stage occurs when a massive star begins producing iron . Since iron nuclei are more tightly bound than any heavier nuclei , any fusion beyond iron does not produce a net release of energy . To a very limited degree such a process proceeds , but it consumes energy . Likewise , since they are more tightly bound than all lighter nuclei , such energy cannot be released by fission . In relatively old , very massive stars , a large core of inert iron will accumulate in the center of the star . The heavier elements in these stars can work their way to the surface , forming evolved objects known as Wolf @-@ Rayet stars that have a dense stellar wind which sheds the outer atmosphere . 
 The final stage <a href='uninflect' title='1'><mark>occurs</mark></a> when a massive star <a href='uninflect' title='2'><mark>begins</mark></a> producing iron . Since iron nuclei <a href='drop_aux' title='3'><mark>are</mark></a>more tightly bound than any heavier nuclei , any fusion beyond iron <a href='uninflect' title='4'><mark>does</mark></a> not produce a net release of energy . To a very limited degree such a process <a href='uninflect' title='5'><mark>proceeds</mark></a> , but it <a href='uninflect' title='6'><mark>consumes</mark></a> energy . Likewise , since they <a href='drop_aux' title='7'><mark>are</mark></a>more tightly bound than all lighter nuclei , such energy cannot be released by fission . In relatively old , very massive stars , a large core of inert iron will accumulate in the center of the star . The heavier elements in these stars can work their way to the surface , forming evolved objects known as Wolf @-@ Rayet stars <a href='null_relcl' title='8'><mark>that</mark></a><a href='got' title='9'><mark>have</mark></a> a dense stellar wind which <a href='uninflect' title='10'><mark>sheds</mark></a> the outer atmosphere . 
The final stage occur when a massive star begin producing iron . Since iron nuclei more tightly bound den any heavier nuclei , any fusion beyond iron do not produce a net release of energy . To a very limited degree such a process proceed , but it consume energy . Likewise , since they more tightly bound tdenalll lighter nuclei , such energy cannot be released by fission . In relatively old , very massive stars , a large core of inert iron gon accumulate in the center of the star . The heavier elements in these stars can wrk their way to the surface , forming evolved objects known as Wolf @-@ Rayet stars got a dense stellar wind which shed da outer atmosphere .