▁then ▁hel ium , ▁progress ing ▁up ▁through ▁the ▁periodic ▁table ▁until ▁a ▁core ▁of ▁iron ▁and ▁nick el ▁is ▁produced . ▁F usion ▁of ▁iron ▁or ▁nick el ▁produces ▁no ▁net ▁energy ▁output , ▁so ▁no ▁further ▁fusion ▁can ▁take ▁place , ▁leaving ▁the ▁nick el – ir on ▁core ▁in ert . ▁Due ▁to ▁the ▁lack ▁of ▁energy ▁output ▁creating ▁out ward ▁thermal ▁pressure , ▁the ▁core ▁contract s ▁due ▁to ▁gravity ▁until ▁the ▁over lying ▁weight ▁of ▁the ▁star ▁can ▁be ▁supported ▁largely ▁by ▁electron ▁deg ener acy ▁pressure . ▁ ▁When ▁the ▁compact ed ▁mass ▁of ▁the ▁in ert ▁core ▁exceed s ▁the ▁Ch andr ase k har ▁limit ▁of ▁about ▁, ▁electron ▁deg ener acy ▁is ▁no ▁longer ▁sufficient ▁to ▁counter ▁the ▁gravit ational ▁compression . ▁A ▁c ata c ly sm ic ▁impl os ion ▁of ▁the ▁core ▁takes ▁place ▁within ▁seconds . ▁Without ▁the ▁support ▁of ▁the ▁now - impl oded ▁inner ▁core , ▁the ▁outer ▁core ▁col laps es ▁in wards ▁under ▁gravity ▁and ▁reaches ▁a ▁velocity ▁of ▁up ▁to ▁ 2 3 % ▁of ▁the ▁speed ▁of ▁light ▁and ▁the ▁sudden ▁compression ▁increases ▁the ▁temperature ▁of ▁the ▁inner ▁core ▁to ▁up ▁to ▁ 1 0 0   b ill ion ▁k el v ins . ▁Ne ut rons ▁and ▁neut r inos ▁are ▁formed ▁via ▁revers ed ▁beta - dec ay , ▁re le asing ▁about ▁ 1 0 4 6   jou les ▁( 1 0 0   fo e ) ▁in ▁a