Subfields of Astronomy
Solar and heliospheric physics is the subfield that studies the Sun: its inner structure, its evolution, the outer corona and the solar wind and radiation in interplanetary space.
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Planetary Physics examines the assemblage of planets, moons, dwarf planets, comets, asteroids, and other bodies orbiting the Sun, as well as extrasolar planets. This has provided a good overall understanding of the formation and evolution of the Solar System, although many new discoveries are still being made.
One of the oldest fields in astronomy, and in all of science, is the measurement of the positions of celestial objects. This field is called now astrometry. Careful measurement of the positions of the planets has led to a solid understanding of celestial mechanics, the field of astronomy that dealing with the motions and gravitational effects of celestial objects.
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The field that studies stars and stellar formation is called stellar astronomy. This field has been historically related with nuclear physics, since the evolution of stars is strongly related with fusion of atom nucleai in their inside.
Galactic astronomy is concerned with the Milky Way galaxy, whereas extragalactic astronomy studies which objects outside our galaxy, including all other galaxies.
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Cosmology considers the study of the universe as a whole.. The understanding of the cosmos as a whole also needs the understanding of the microcosmos, i.e Particle Physics, and other theoretical studies, such as gravitation. The collaboration among these different areas of physics is thus essential.
Finally there are also interdisciplinary subfields whose object of study is both astronomical and of another major science. Astrobiology, for instance, is the study of the advent and evolution of biological systems in the universe. It is also concerned with the search for life outside the earth and with the effects of extraterrestrial environments on living organisms. Archaeoastronomy is the study of ancient or traditional astronomies in their cultural context, utilizing archaeological and anthropological evidence. Astrochemistry is the study of the chemicals found in space, usually in molecular clouds, and their formation, interaction and destruction. It represents an overlap of the disciplines of astronomy and chemistry. Cosmochemistry is the study of the chemicals found within the Solar System, including the origins of the elements and variations in the isotope ratios.
Other possible astronomical subdisciplines are: Compact objects astrophysics, exoplanetary astronomy, galaxy formation and evolution, high energy astrophysics, interstellar astrophysics, intergalactic medium and dust, plasma astrophysics, relativistic astrophysics, stellar evolution, star formation, planetary atmospheric science, planetary formation, planetary rings, magnetospheres, planetary interiors, small solar system objects astronomy.