The crossword solution for the term 'Subject for Galileo' is SATURN, which is a 6-letter word. Galileo Galilei was an Italian astronomer and physicist who is credited with making major contributions to the fields of astronomy, physics, and science in general. He is best known for his observations of the planet SATURN, which he made using a telescope he built himself. He was the first to observe and document the rings of SATURN, as well as its four largest moons.