Revising for Specificity in Interests

Read the following passage and answer the question that follows:

Tom had always been fascinated by the stars. As a child, he would spend countless nights lying on the grass, gazing up at the vast sky. His interest in astronomy only grew as he read books and watched documentaries about the universe. Over time, he dreamed of becoming an astrophysicist and contributing to mankind's understanding of the cosmos.

What is the best way to revise the sentence in bold to make it more specific? "His interest in astronomy only grew as he read books and watched documentaries about the universe."