▁super n ova . ▁ ▁When ▁the ▁lum inos ity ▁of ▁a ▁Type   II ▁super n ova ▁is ▁pl otted ▁over ▁a ▁period ▁of ▁time , ▁it ▁shows ▁a ▁characteristic ▁rise ▁to ▁a ▁peak ▁bright ness ▁followed ▁by ▁a ▁decl ine . ▁These ▁light ▁curves ▁have ▁an ▁average ▁decay ▁rate ▁of ▁ 0 . 0 0 8   m agn itudes ▁per ▁day ; ▁much ▁lower ▁than ▁the ▁decay ▁rate ▁for ▁Type   I a ▁super nov ae . ▁Type   II ▁is ▁sub div ided ▁into ▁two ▁classes , ▁depending ▁on ▁the ▁shape ▁of ▁the ▁light ▁curve . ▁The ▁light ▁curve ▁for ▁a ▁Type   II - L ▁super n ova ▁shows ▁a ▁steady ▁( linear ) ▁decl ine ▁following ▁the ▁peak ▁bright ness . ▁By ▁contrast , ▁the ▁light ▁curve ▁of ▁a ▁Type   II - P ▁super n ova ▁has ▁a ▁distinct ive ▁flat ▁stretch ▁( called ▁a ▁plate au ) ▁during ▁the ▁decl ine ; ▁representing ▁a ▁period ▁where ▁the ▁lum inos ity ▁dec ays ▁at ▁a ▁slower ▁rate . ▁The ▁net ▁lum inos ity ▁decay ▁rate ▁is ▁lower , ▁at ▁ 0 . 0 0 7 5   m agn itudes ▁per ▁day ▁for ▁Type   II - P , ▁compared ▁to ▁ 0 . 0 1 2   m agn itudes ▁per ▁day ▁for ▁Type   II - L . ▁ ▁The ▁difference ▁in ▁the ▁shape ▁of ▁the ▁light ▁curves ▁is ▁believed ▁to ▁be ▁caused , ▁in ▁the ▁case ▁of ▁Type   II - L ▁super