What is the primary focus of astrophysics?

The primary focus of astrophysics is the study of space and celestial bodies, which encompasses a wide range of phenomena and objects in the universe. This field seeks to understand the physical properties, behaviors, and interactions of stars, planets, galaxies, and the broader cosmos. Astrophysics integrates principles from physics and astronomy to explore questions related to the formation, evolution, and ultimate fate of celestial objects, as well as the underlying laws that govern their behavior.

While studying planets and moons is indeed a component of astrophysics, it is too narrow to encompass the entire field, as astrophysics also includes investigations of stars, galaxies, black holes, and cosmology. Furthermore, although understanding chemical reactions in stars is an important aspect of astrophysics, it represents only a specific area within the broader discipline. Lastly, researching extraterrestrial life is related to astrophysics but is more aligned with astrobiology and does not capture the full scope of astrophysical studies. Therefore, the broad and inclusive nature of space and celestial bodies as a central focus rightly identifies option two as the correct answer.