<Ul> <Li> <P> Protoplanetary disc AS 209 nestled in the young Ophiuchus star - forming region . </P> </Li> <Li> <P> Protoplanetary disk HH 212 . </P> </Li> <Li> <P> By observing dusty protoplanetary discs, scientists investigate the first steps of planet formation . </P> </Li> <Li> <P> Concentric rings around young star HD 141569A, located some 370 light - years away . </P> </Li> <Li> <P> Debris disks detected in HST images of young stars, HD 141943 and HD 191089 - images at top; geometry at bottom . </P> </Li> <Li> <P> Protoplanetary disk HH - 30 in Taurus - disk emits the reddish stellar jet . </P> </Li> <Li> <P> Artist's impression of a protoplanetary disk . </P> </Li> <Li> <P> A proplyd in the Orion Nebula . </P> </Li> <Li> Play media <P> Video shows the evolution of the disc around a young star like HL Tauri (artist concept). </P> </Li> </Ul> <Li> <P> Protoplanetary disc AS 209 nestled in the young Ophiuchus star - forming region . </P> </Li> <P> Protoplanetary disc AS 209 nestled in the young Ophiuchus star - forming region . </P> <Li> <P> Protoplanetary disk HH 212 . </P> </Li>

Because of the temperatures in the protoplanetary disk