( Thus ( , ( ( Type ( II supernovae ) ) ( ( are ( ( ( ( ( the ( only source ) ) ( -LRB- ( ( in ( ( today 's ) universe ) ) -RRB- ) ) ) ( of ( all elements ) ) ) heavier ) ( than ( iron ( -LRB- ( ( which ( are ( ( much ( less abundant ) ) ( than ( the ( lighter ones ) ) ) ) ) ) -RRB- ) ) ) ) ) ) . ) ) ) )
(ROOT (S (ADVP (RB Thus)) (, ,) (NP (NNP Type) (NNP II) (NNP supernovae)) (VP (VBP are) (ADJP (ADJP (NP (NP (NP (DT the) (JJ only) (NN source)) (PRN (-LRB- -LRB-) (PP (IN in) (NP (NP (NN today) (POS 's)) (NN universe))) (-RRB- -RRB-))) (PP (IN of) (NP (DT all) (NNS elements)))) (JJR heavier)) (PP (IN than) (NP (NP (NN iron)) (PRN (-LRB- -LRB-) (SBAR (WHNP (WDT which)) (S (VP (VBP are) (ADJP (ADJP (RB much) (RBR less) (JJ abundant)) (PP (IN than) (NP (DT the) (JJR lighter) (NNS ones))))))) (-RRB- -RRB-)))))) (. .)))
Thus, Type II supernovae are the only source (in today's universe) of all elements heavier than iron (which are much less abundant than the lighter ones).
(ROOT (S (NP (NNS Supernovas)) (VP (VBP are) (ADJP (ADJP (NP (NP (DT the) (NN source)) (PP (IN of) (NP (NNS elements)))) (JJR heavier)) (PP (IN than) (NP (NN iron))))) (. .)))