apparition

An act of becoming visible; appearance; visibility.

The thing appearing; a visible object; a form.

An unexpected, wonderful, or preternatural appearance; especially something such as a ghost or phantom.

(astronomy) The first appearance of a star or other luminary after having been invisible or obscured; opposed to occultation.

(astronomy) A period of consecutive days or nights when a particular celestial body may be observed, beginning with the heliacal rising of the body and ending with its heliacal setting.