Catechism of the Catholic Church §665 — excerpt
Christ's Ascension marks the definitive entrance of Jesus' humanity into God's heavenly domain, whence he will come again (cf Acts 1:11); this humanity in the meantime hides him from the eyes of men (cf Col 3:3).
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.