From the Moon, a star rises and/or sets once every 27.3 days, so an event is unlikely to happen on a given calendar day.
(a star; rises; L:From the Moon) (a star; sets; T:once; every 27.3 days) (an event; is; unlikely to happen on a given calendar day) (an event; to happen; T:on a given calendar day)
a star a star an event an event
rises sets is to happen
L:From the Moon
T:once every 27.3 days
unlikely to happen on a given calendar day
T:on a given calendar day