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Astronomy is a natural science that deals with the study of celestial objects (such as moons , planets , stars , nebulae , and galaxies ); the physics, chemistry, and evolution of such objects; and phenomena that originate outside the atmosphere of Earth (such as supernovae explosions , gamma ray bursts , and cosmic background radiation ). A related but distinct subject, cosmology , is concerned with studying the universe as a whole. [ 1 ] Astronomy is one of the oldest sciences.
Space physics , also known as space plasma physics , is the study of plasmas as they occur naturally in the universe . As such, it encompasses a far-ranging number of topics, including the sun , solar wind , planetary magnetospheres and ionospheres , auroras , cosmic rays , and synchrotron radiation .
Plasma (from Greek πλάσμα, "anything formed" [ 1 ] ) is one of the four fundamental states of matter (the others being solid , liquid , and gas ).
Planetary science (rarely planetology ) is the scientific study of planets (including Earth ), moons , and planetary systems , in particular those of the Solar System and the processes that form them.
High energy astronomy is the study of astronomical objects that release EM radiation of highly energetic wavelengths . It includes X-ray astronomy , gamma-ray astronomy , and extreme UV astronomy , as well as studies of neutrinos and cosmic rays . The physical study of these phenomena is referred to as high-energy astrophysics . [ 1 ]
Gravitation , or gravity , is the natural phenomenon by which physical bodies appear to attract each other with a force proportional to their masses . It is most commonly experienced as the agent that gives weight to objects with mass and causes them to fall to the ground when dropped.
Physical cosmology , as a branch of astronomy , is the study of the largest-scale structures and dynamics of the universe and is concerned with fundamental questions about its formation and evolution. [ 1 ] For most of human history, it was a branch of metaphysics and religion .