( ( ( ( ( 0-4622 '' ) ( can ( be ( attributed ( to ( ( ( a ( low ( matter density ) ) ) ( of ( ( just 0.04 ) ( gas ( and ( dust particles ) ) ) ) ) ) ( per cubic-centimeter ) ) ) ) ) ) ) , ) ( ( surrounding ( the star ) ) ( before ( it exploded ) ) ) ) . )
(ROOT (S (VP (NP (NP (CD 0-4622)) ('' '') (SBAR (S (VP (MD can) (VP (VB be) (VP (VBN attributed) (PP (TO to) (NP (NP (DT a) (JJ low) (NN matter) (NN density)) (PP (IN of) (NP (QP (RB just) (CD 0.04)) (NN gas) (CC and) (NN dust) (NNS particles))) (PP (IN per) (NP (NN cubic-centimeter)))))))))) (, ,) (VP (VBG surrounding) (NP (DT the) (NN star)) (SBAR (IN before) (S (NP (PRP it)) (VP (VBD exploded))))))) (. .)))
0-4622&quot; can be attributed to a low matter density of just 0.04 gas and dust particles per cubic-centimeter, surrounding the star before it exploded.
(ROOT (S (NP (NNS Gases)) (VP (VBP have) (NP (DT the) (JJS lowest) (NN density))) (. .)))