The Belgian church established the Catholic University of Louvain in 1834, nowadays split into the Université catholique de Louvain and the Katholieke Universiteit Leuven, which together comprise the largest university in Belgium. The archbishop of Mechelen is "ex officio" the Great Chancellor of both universities. Founded in Mechlin by the bishops of Belgium in 1834, the Catholic University moved to Leuven in 1835 to replace the State University of Leuven which was closed the same year. Some of its most notable graduates include Georges Lemaître, priest, astronomer, and proposer of the Big Bang theory, Otto von Habsburg, former head of the Habsburg family, Saint Alberto Hurtado, Chilean Jesuit priest who was canonised in 2005, Charles Jean de la Vallée-Poussin, mathematician who proved the prime number theorem, Christian de Duve, winner of the Nobel Prize in Medicine in 1974, among others. The Belgian church also oversees the Basilica of the Sacred Heart, the National Basilica of Belgium.