Outline of astronomy explained

The following outline is provided as an overview of and topical guide to astronomy:

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). Astronomy also intersects with biology, as astrobiology, studying potential life throughout the universe.

Nature of astronomy

Astronomy can be described as all the following:

An academic discipline: one with academic departments, curricula and degrees; national and international societies; and specialized journals.
A scientific field (a branch of science) – widely recognized category of specialized expertise within science, and typically embodies it
- A natural science – one that seeks to elucidate the rules that govern the natural world using empirical and scientific methods.
  - A branch or field of space science
A hobby or part-time pursuit for the satisfaction of personal curiosity or appreciation of beauty, the latter especially including astrophotography.

Branches of astronomy

Astrobiology – studies the advent and evolution of biological systems in the universe.
Astrophysics – branch of astronomy that deals with the physics of the universe, including the physical properties of celestial objects, as well as their interactions and behavior.^[1] ^[2] Among the objects studied are galaxies, stars, planets, exoplanets, the interstellar medium and the cosmic microwave background; and the properties examined include luminosity, density, temperature, and chemical composition. The subdisciplines of theoretical astrophysics are:
- Compact objects – this subdiscipline studies very dense matter in white dwarfs and neutron stars and their effects on environments including accretion.
- Physical cosmology – origin and evolution of the universe as a whole. The study of cosmology is theoretical astrophysics at its largest scale.
- Quantum cosmology - the study of cosmology through the use of quantum field theory to explain phenomena general relativity cannot due to limitations in its framework.
- Computational astrophysics – The study of astrophysics using computational methods and tools to develop computational models.
- Galactic astronomy – deals with the structure and components of our Galaxy and of other galaxies.
- High energy astrophysics – studies phenomena occurring at high energies including active galactic nuclei, supernovae, gamma-ray bursts, quasars, and shocks.
- Interstellar astrophysics – study of the interstellar medium, intergalactic medium and dust.
- Extragalactic astronomy – study of objects (mainly galaxies) outside our Galaxy, including galaxy formation and evolution.
- Stellar astronomy – concerned with Star formation, physical properties, main sequence life span, variability, stellar evolution and extinction.
- Plasma astrophysics – studies properties of plasma in outer space.
- Relativistic astrophysics – studies effects of special relativity and general relativity in astrophysical contexts including gravitational waves, gravitational lensing and black holes.
- Solar physics – Sun and its interaction with the remainder of the Solar System and interstellar space.
Planetary Science – study of planets, moons, and planetary systems.
- Atmospheric science – study of atmospheres and weather.
- Exoplanetology – various planets outside of the Solar System
- Planetary formation – formation of planets and moons in the context of the formation and evolution of the Solar System.
- Planetary rings – dynamics, stability, and composition of planetary rings
- Magnetospheres – magnetic fields of planets and moons
- Planetary surfaces – surface geology of planets and moons
- Planetary interiors – interior composition of planets and moons
- Small Solar System bodies – smallest bodies, including asteroids, comets, Kuiper belt objects, and dust.
Astronomy divided by general technique used for astronomical research:
- Astrometry – study of the position of objects in the sky and their changes of position. Defines the system of coordinates used and the kinematics of objects in our Galaxy.
- Observational astronomy – practice of observing celestial objects by using telescopes and other astronomical apparatus. It is concerned with recording data. The subdisciplines of observational astronomy are generally made by the specifications of the detectors, specifically the ranges of wavelengths observed:
  - Radio astronomy – Above 300 μm
  - Submillimetre astronomy – 200 μm to 1 mm
  - Infrared astronomy – 0.7–350 μm
  - Optical astronomy – 380–750 nm
  - Ultraviolet astronomy – 10–320 nm
  - X-ray astronomy – 0.01–10 nm
  - Gamma-ray astronomy – Below 0.01 nm
  - Cosmic ray astronomy – Cosmic rays, including plasma
  - Neutrino astronomy – Neutrinos
  - Dust astronomy – Cosmic dust
  - Gravitational wave astronomy – Gravitons
- Photometry – study of how bright celestial objects are when passed through different filters
- Spectroscopy – study of the spectra of astronomical objects
Other disciplines that may be considered part of astronomy:
- Archaeoastronomy
- Astrochemistry

History of astronomy

History of the Center of the Universe
- Geocentric model
- Heliocentrism
  - Copernican heliocentrism
  - Tychonic system
Archaeoastronomy
- Archaeoastronomy and Vedic chronology
  - Pretelescopic astronomy Babylonian astronomy
- Chinese astronomy
- Egyptian astronomy
- Greek astronomy
- Hebrew astronomy
- Indian astronomy
- Islamic astronomy
- Russian astronomy
- Astronomy in the Middle Ages
  - Science in Medieval Western Europe
  - Astronomy in medieval Islam
History of astronomy in the Renaissance
- Scientific developments during the Scientific Revolution
  - Patronage in astronomy
  - Copernican Revolution
    - Copernican heliocentrism
    - Nicolaus Copernicus
      - On the Revolutions of the Heavenly Spheres
    - Tycho Brahe
      - Tychonic system
    - Galileo Galilei
      - Dialogue Concerning the Two Chief World Systems defense of the heliocentric system written by Galileo, which led to his trial and house arrest by the Inquisition.
  - Invention of the telescope
    - History of visible-light astronomy
History of astronomy in the Age of Reflection
- History of X-ray astronomy
History of infrared astronomy
History of gamma-ray astronomy
History of supernova observation
- List of supernovae

Basic astronomical phenomena

Astronomical objects

Astronomical object

Solar System

Exoplanets

Exoplanet (also known as extrasolar planets) – planet outside the Solar System. A total of 4,341 such planets have been identified as of 28 Jan 2021.
- Super-Earth – exoplanet with a mass higher than Earth's, but substantially below those of the Solar System's ice giants.
- Mini-Neptune – also known as a gas dwarf or transitional planet. A planet up to 10 Earth masses, but less massive than Uranus and Neptune.
- Super-Jupiter – an exoplanet more massive than Jupiter.
- Sub-Earth – an exoplanet "substantially less massive" than Earth and Venus.
- Circumbinary planet – an exoplanet that orbits two stars.
- Hot Jupiter – an exoplanet whose characteristics are similar to Jupiter, but that have high surface temperatures because they orbit very close to their parent stars, whereas Jupiter orbits its parent star (the Sun) at 5.2 AU (780×106 km), causing low surface temperatures.
- Hot Neptune – an exoplanet in an orbit close to its star (normally less than one astronomical unit away), with a mass similar to that of Uranus or Neptune.
- Pulsar planet – a planet that orbits a pulsar or a rapidly rotating neutron star.
- Rogue planet (also known as an interstellar planet) – a planetary-mass object that orbits the galaxy directly.