Simplify the following text for a Grade 9 native English-speaking person.
Original: All doubts were erased when Pluto and Charon entered a five-year period of mutual eclipses and transits between 1985 and 1990 .
Simplified: Any final doubts were erased when Pluto and Charon entered a five-year period of mutual eclipses between 1985 and 1990 .