Astronomy is the science of celestial objects and phenomena that originate outside the Earth's atmosphere. It is concerned with the evolution, physics, chemistry, meteorology, and motion of celestial objects, as well as the formation and development of the universe.

There are two levels of general astronomy. The first refers to courses that provide a broad, but relatively superficial, view of astronomy. Such programs are often taught as science requirements for non-science majors. The second level refers to the non-technical aspects of astronomy, such as history, philosophy, and the social impact of astronomy,

The Solar System consists of the sun and all the planets, moons, and other natural objects that are gravitationally bound to it.  Solar system astronomy is thus the specialized study of that system.

Studies of stellar and galactic astronomy refer to the evolution and physics of stars in our Milky Way galaxy as well as the Milky Way galaxy, itself. Traditional study programs might refer to extragalactic subjects, but do not deal with those subjects in great detail. Extragalactic subjects are thus covered in departments of cosmology and astrophysics.

Cosmology and Astrophysics

Cosmology is the branch of metaphysics that deals with the origin, structure, and space-time relationships of the universe or a theory or doctrine describing the natural order of the universe. Astrophysics relies on the established physics and chemistry as applied to celestial objects.

Derived from Wikipedia