The technical definition of a spectral highlight is "A bright reflection from a light source containing little or no detail. " Essentially this portion of light is too bright for the digital camera's sensor to capture, so you end up with a white spot or streak in your picture. Reflections often cause this as does shooting towards the sun or other light source. However when using the Lensbaby with a star shaped aperture insert, those out of focus spectral highlights take on the shape of a star. This is our Christmas tree with its white lights. Canon 7D, 1/8 sec @ ~f/2.8, ISO 200 with the Lensbaby.
From 365 Project The Air Force Memorial in glows against low hanging clouds and mist. Located on a promontory in Arlington, Virginia, overlooking the Pentagon and adjacent to Arlington Cemetery, the memorial's three 270 feet tall stainless arcs evoke the spirit of flight. Taken with a Canon 40D, 5.0s exposure at f/8.0, ISO 200, 28mm equivalent focal length, mounted on a tripod.