Planetary science is
the branch of astronomy dealing with the characteristics
(structure, atmosphere, history) of planets.
The term is used largely for solar system objects,
including planets, moons, asteroids, comets, etc.
It can be thought of as Earth science generalized so as to
apply to other planets and similar bodies.
Extra-solar planet studies fall under the term: while
exoplanets have certainly affected the view of
planet formation and planetary migration
within the solar system,
much of the connection is the application of what
has been learned about planets within the solar system
to analyze the limited information available
from exoplanet observations.