The term 'Guiding Heavenly Body' can be summarized as a LODESTAR, which is an 8-letter word. A LODESTAR is a star that is used to guide travelers and navigators, such as the North Star. It is also known as a polar star, as it is located close to the North Pole in the night sky. Lodestars have been used for centuries to help people find their way, and they are still used today by sailors and other navigators.