 Several models were devised to compute the density and size of Shoemaker – Levy 9 . Its average density was calculated to be about 0 @.@ 5 g cm − 3 ; the breakup of a much less dense comet would not have resembled the observed string of objects . The size of the parent comet was calculated to be about 1 @.@ 8 km in diameter . These predictions were among the few that were actually confirmed by subsequent observation . 
