Question: What is the branch of astronomy that deals with the physics of the universe?
About the article "Astrophysics", section "Abstract".

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Solar astronomy is stellar astronomy of the Sun.
A major branch of Solar astronomy is Solar physics. 
Generally, either the term "astronomy" or "astrophysics" may be used to refer to this subject.
Based on strict dictionary definitions, "astronomy" refers to "the study of objects and matter outside the Earth's atmosphere and of their physical and chemical properties" and "astrophysics" refers to the branch of astronomy dealing with "the behavior, physical properties, and dynamic processes of celestial objects and phenomena".
In some cases, as in the introduction of the introductory textbook "The Physical Universe" by Frank Shu, "astronomy" may be used to describe the qualitative study of the subject, whereas "astrophysics" is used to describe the physics-oriented version of the subject.
However, since most modern astronomical research deals with subjects related to physics, modern astronomy could actually be called astrophysics.
Few fields, such as astrometry, are purely astronomy rather than also astrophysics.
Various departments in which scientists carry out research on this subject may use "astronomy" and "astrophysics," partly depending on whether the department is historically affiliated with a physics department, and many professional astronomers have physics rather than astronomy degrees.
One of the leading scientific journals in the field is the European journal named Astronomy and Astrophysics.
The leading American journals are The Astrophysical Journal and The Astronomical Journal. 
Based on strict dictionary definitions, "astronomy" refers to "the study of objects and matter outside the Earth's atmosphere and of their physical and chemical properties" In some cases, as in the introduction of the introductory textbook "The Physical Universe" by Frank Shu, "astronomy" may be used to describe the qualitative study of the subject.
Astronomy focuses on celestial objects, space, and the physical universe as a whole.
Observations of the Sun, Moon, stars, and planets have formed the basis of timekeeping and navigation.
Astronomy is a branch of science, but unlike other sciences, which have Earth-based laboratories in which controlled experiments are performed, astronomy has its labs located in the heavens far beyond the reach, let alone control, of the terrestrial observer.
"So how can one be sure that what one sees out there is subject to the same rules and disciplines of science that govern the local laboratory experiments of physics and chemistry?"
"The most incomprehensible thing about the universe is that it is comprehensible.
" – Albert Einstein.
Ptolemy's Almagest, although a brilliant treatise on theoretical astronomy combined with a practical handbook for computation, nevertheless includes many compromises to reconcile discordant observations.
Theoretical astronomy is usually assumed to have begun with Johannes Kepler (1571–1630), and Kepler's laws.
It is co-equal with observation.
The general history of astronomy deals with the history of the descriptive and theoretical astronomy of the solar system, from the late sixteenth century to the end of the nineteenth century.
The major categories of works on the history of modern astronomy include general histories, national and institutional histories, instrumentation, descriptive astronomy, theoretical astronomy, positional astronomy, and astrophysics.
Astronomy was early to adopt computational techniques to model stellar and galactic formation and celestial mechanics.
From the point of view of theoretical astronomy, not only must the mathematical expression be reasonably accurate but it should preferably exist in a form which is amenable to further mathematical analysis when used in specific problems.
Most of theoretical astronomy uses Newtonian theory of gravitation, considering that the effects of general relativity are weak for most celestial objects.
The obvious fact is that theoretical astronomy cannot (and does not try) to predict the position, size and temperature of every star in the heavens.
Theoretical astronomy by and large has concentrated upon analyzing the apparently complex but periodic motions of celestial objects. 
Natural sciences.
Physical sciences.
Physics – study of matter and its motion through space-time, along with related concepts such as energy and force  Acoustics – study of mechanical waves in solids, liquids, and gases (such as vibration and sound)  Agrophysics – study of physics applied to agroecosystems * Soil physics – study of soil physical properties and processes.
Astrophysics – study of the physical aspects of celestial objects Astronomy – studies the universe beyond Earth, including its formation and development, and the evolution, physics, chemistry, meteorology, and motion of celestial objects (such as galaxies, planets, etc.)
and phenomena that originate outside the atmosphere of Earth (such as the cosmic background radiation).
Astrodynamics – application of ballistics and celestial mechanics to the practical problems concerning the motion of rockets and other spacecraft.
* Astrometry – branch of astronomy that involves precise measurements of the positions and movements of stars and other celestial bodies.
* Cosmology – discipline that deals with the nature of the Universe as a whole.
* Extragalactic astronomy – branch of astronomy concerned with objects outside our own Milky Way Galaxy * Galactic astronomy – study of our own Milky Way galaxy and all its contents.
* Physical cosmology – study of the largest-scale structures and dynamics of the universe and is concerned with fundamental questions about its formation and evolution.
* Planetary science – scientific study of planets (including Earth), moons, and planetary systems, in particular those of the Solar System and the processes that form them.
* Stellar astronomy – natural science that deals with the study of celestial objects (such as stars, planets, comets, nebulae, star clusters and galaxies) and phenomena that originate outside the atmosphere of Earth (such as cosmic background radiation) * Atmospheric physics – study of the application of physics to the atmosphere  Atomic, molecular, and optical physics – study of how matter and light interact  Biophysics – study of physical processes relating to biology * Medical physics – application of physics concepts, theories and methods to medicine.
* Neurophysics – branch of biophysics dealing with the nervous system.
Chemical physics – branch of physics that studies chemical processes from the point of view of physics.
Computational physics – study and implementation of numerical algorithms to solve problems in physics for which a quantitative theory already exists.
Condensed matter physics – study of the physical properties of condensed phases of matter.
Cryogenics – cryogenics is the study of the production of very low temperature (below –150 °C, –238°F or 123K) and the behavior of materials at those temperatures.
Dynamics – study of the causes of motion and changes in motion  Econophysics – interdisciplinary research field, applying theories and methods originally developed by physicists in order to solve problems in economics  Electromagnetism – branch of science concerned with the forces that occur between electrically charged particles.
Geophysics – the physics of the Earth and its environment in space; also the study of the Earth using quantitative physical methods  Materials physics – use of physics to describe materials in many different ways such as force, heat, light and mechanics.
Mathematical physics – application of mathematics to problems in physics and the development of mathematical methods for such applications and for the formulation of physical theories.
Mechanics – branch of physics concerned with the behavior of physical bodies when subjected to forces or displacements, and the subsequent effects of the bodies on their environment.
* Biomechanics – study of the structure and function of biological systems such as humans, animals, plants, organs, and cells by means of the methods of mechanics.
* Classical mechanics – one of the two major sub-fields of mechanics, which is concerned with the set of physical laws describing the motion of bodies under the action of a system of forces.
* Continuum mechanics – branch of mechanics that deals with the analysis of the kinematics and the mechanical behavior of materials modeled as a continuous mass rather than as discrete particles.
* Fluid mechanics – study of fluids and the forces on them.
* Quantum mechanics – branch of physics dealing with physical phenomena where the action is on the order of the Planck constant.
* Thermodynamics – branch of physical science concerned with heat and its relation to other forms of energy and work.
Nuclear physics – field of physics that studies the building blocks and interactions of atomic nuclei.
Optics – branch of physics which involves the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it.
Particle physics – branch of physics that studies the existence and interactions of particles that are the constituents of what is usually referred to as matter or radiation.
Psychophysics – quantitatively investigates the relationship between physical stimuli and the sensations and perceptions they affect.
Plasma physics – state of matter similar to gas in which a certain portion of the particles are ionized.
Polymer physics – field of physics that studies polymers, their fluctuations, mechanical properties, as well as the kinetics of reactions involving degradation and polymerisation of polymers and monomers respectively.
Quantum physics – branch of physics dealing with physical phenomena where the action is on the order of the Planck constant.
Relativity –  Statics – branch of mechanics concerned with the analysis of loads (force, torque/moment) on physical systems in static equilibrium, that is, in a state where the relative positions of subsystems do not vary over time, or where components and structures are at a constant velocity.
Solid state physics – study of rigid matter, or solids, through methods such as quantum mechanics, crystallography, electromagnetism, and metallurgy.
Vehicle dynamics – dynamics of vehicles, here assumed to be ground vehicles.  
Solar physics is the branch of astrophysics that specializes in the study of the Sun.
It deals with detailed measurements that are possible only for our closest star.
It intersects with many disciplines of pure physics, astrophysics, and computer science, including fluid dynamics, plasma physics including magnetohydrodynamics, seismology, particle physics, atomic physics, nuclear physics, stellar evolution, space physics, spectroscopy, radiative transfer, applied optics, signal processing, computer vision, computational physics, stellar physics and solar astronomy.
Because the Sun is uniquely situated for close-range observing (other stars cannot be resolved with anything like the spatial or temporal resolution that the Sun can), there is a split between the related discipline of observational astrophysics (of distant stars) and observational solar physics.
The study of solar physics is also important as it is believed that changes in the solar atmosphere and solar activity can have a major impact on Earth's climate.
The Sun also provides a "physical laboratory" for the study of plasma physics.