Benedict XVI ceased to be pope at 8 p.m. local time (2 p.m. Eastern) Thursday when his resignation took effect, leaving the leadership of the Roman Catholic Church vacant while its leading clerics consider who should succeed him.

Benedict left the Vatican by helicopter on Thursday afternoon to spend the final hours of his scandal-dogged papacy and the first of his retirement at a summer residence used by popes for centuries. Onlookers in St. Peter’s Square cheered, church bells rang and Romans stood on rooftops to wave flags to see him off as he flew from Rome to the summer residence at Castel Gandolfo, a hilltop town southeast of the city. More carillons heralded his arrival there, and he was greeted by a vivid contingent of...