The following outline is provided as an overview of and topical guide to astrophysics.
Description of astrophysics Astrophysics can be described as all of the following:
An academic discipline – with academic departments, curricula and degrees; national and international societies; and specialized journals. A scientific field (a branch of science) – a widely recognized category of specialized expertise within science, with its own terminology and nomenclature and dedicated peer‑reviewed journals. 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 scientific discipline that involves space exploration and studies natural phenomena and physical bodies occurring in outer space. A branch of astronomy – the study of celestial objects, space, and the universe as a whole. A branch of physics – the fundamental science that studies matter, energy, and their interactions. An interdisciplinary field – a field of science that overlaps with other sciences such as physics, astronomy, planetary science, and computer science.
Branches of astrophysics
Stellar astronomy – study of star formation, physical properties, life spans, variability, stellar evolution, and end states. Asteroseismology – study of oscillations in stars. Helioseismology – study of the oscillations of the Sun. Stellar chemistry – study of chemical compositions and abundance patterns in stars and their implications for stellar and galactic evolution. Solar physics – study of the Sun, its structure and activity, and its interaction with the rest of the Solar System and interstellar space. Celestial mechanics – Study of motion and gravitation of astronomical objects. Exoplanet science – detection and characterization of planets outside the Solar System and their atmospheres. Galactic astronomy – study of the structure and components of the Milky Way and of other galaxies. Extragalactic astronomy – study of objects (mainly galaxies) outside the Milky Way, including galaxy formation and evolution. Physical cosmology – study of the origin, structure, evolution, and ultimate fate of the universe as a whole. Quantum cosmology – study of the universe using quantum field theory and related quantum frameworks to address problems beyond classical general relativity. Fractal cosmology – Models inhomogeneous universe structure on large scales. Gravitational-wave astronomy – study of astrophysical sources of gravitational waves and the information they carry. High-energy astronomy – study of astronomical objects and phenomena that involve highly energetic radiation and particles, such as active galactic nuclei, supernovae, gamma-ray bursts, quasars, and shocks. Gamma-ray astronomy – study of the universe at gamma-ray wavelengths. X-ray astronomy – study of astronomical objects that emit X-rays. Ultraviolet astronomy – study of astronomical objects at ultraviolet wavelengths. Astroparticle physics – study of particles of astronomical origin (such as cosmic rays, neutrinos, and gamma rays) and their interactions with matter. Cosmic ray astronomy – study of cosmic rays and their astrophysical sources. Neutrino astronomy – use of neutrinos to study astrophysical sources and processes. Interstellar astrophysics – study of the interstellar medium, intergalactic medium, and dust. Atomic and molecular astrophysics – study of atomic and molecular processes in astrophysical environments, including star and planet formation. Plasma astrophysics – study of the properties and behavior of plasma in space and astrophysical environments. Space plasma physics – Study of collisionless plasmas in space environments. Nuclear astrophysics – study of nuclear reactions in astrophysical environments and their role in energy generation and nucleosynthesis. Nucleocosmochronology – use of the abundances of radioactive nuclides to estimate the ages of astronomical objects and the universe. Cosmochemistry – study of the chemical composition of matter in the universe and the processes that led to those compositions. Relativistic astrophysics – study of phenomena in which special and general relativity play an essential role, including gravitational waves, gravitational lensing, and black holes. Astrobiology – study of the origin, evolution, distribution, and future of life in the universe. Astrobiophysics – study of how astrophysical phenomena influence life on Earth and hypothetically on other planets. Computational astrophysics – use of computational methods and numerical simulations to develop and test models of astrophysical systems.
Universe structure and evolution
Astrophysical objects
Stars and stellar remnants: Main‑sequence stars Giant stars and supergiants Red giant – Late evolutionary stage with expanded envelope. White dwarfs Neutron stars Black holes – region in space where the gravitational pull is so strong that nothing can escape from it. Przybylski's Star – Exhibits anomalous heavy elements, challenging diffusion theories. SDSS J120136.02+300305.5 – Quasar exemplifying supermassive black hole seed growth. Planetary systems: Planets Exoplanets Protoplanetary disks Brown dwarfs Rubble pile – Aggregate structure of large asteroids from collision debris. Amorphous carbonia – High-pressure carbon phase relevant to interiors of icy planets and exoplanets. Galaxies and large‑scale structures: Dwarf galaxies Spiral galaxies Milky Way – the galaxy where Earth is located. Alaknanda Galaxy – ancient grand‑design spiral whose unexpectedly mature structure only 1.5 billion years after the Big Bang challenges standard models of how quickly massive disk galaxies can form. Galaxy clusters Superclusters Cosmic web
Astrophysical phenomena
Supernovae and hypernovae Supernova nucleosynthesis – Produces iron-peak elements and r-process isotopes. Iron peak – Nucleosynthesis endpoint around iron group elements in supernovae. Nucleosynthesis – process by which elements are formed through nuclear reactions in stars and in the early universe. Gamma-ray bursts Active galactic nuclei and quasars SDSS J120136.02+300305.5 – Quasar exemplifying supermassive black hole seed growth. Accretion (astrophysics) Accretion disks Astrophysical jets and outflows Stellar flares and coronal mass ejections Pulsars and magnetars Gravitational lensing – bending of light from a distant object due to the gravitational field of a massive object between it and the observer. Cosmic microwave background radiation Axis of evil (cosmology) – CMB alignment anomaly challenging isotropy assumptions. Dark matter – form of matter that does not emit, absorb, or reflect light, inferred from its gravitational effects. and dark energy – hypothetical form of energy that permeates space and drives the accelerated expansion of the universe. Reionization – Epoch when first stars ionized intergalactic hydrogen. Planck scale – Fundamental limit where quantum gravity dominates early universe. Causal dynamical triangulation – Quantum gravity approach simulating universe emergence at Planck scales.
Chemical evolution Abundance of the chemical elements – Quantifies elemental distributions in the universe. Metallicity distribution function – Statistical tool for galactic chemical evolution. S-process – Slow neutron capture producing heavy elements in AGB stars. P-nuclei – Rare isotopes synthesized in supernovae.
Stellar & solar signatures Stellar pulsation – Oscillations revealing stellar interiors via asteroseismology. Frequency separation – Asteroseismic diagnostic of stellar core rotation. Solar radio emission – Emission from solar corona tracing magnetic activity. Standard solar model – Predicts neutrino fluxes testing particle physics.
Interstellar diagnostics Photodissociation region – Interfaces where UV photons dissociate molecules in nebulae. X-factor – Converts CO emission to molecular hydrogen mass. Radio Recombination Lines – Emission from ionized nebulae tracing temperature and density. Strömgren integral – Computes H II region size around hot stars. Zanstra method – Determines nebula electron density from emission lines. Interstellar medium – matter that exists in the space between stars in a galaxy.
High-energy signatures Extragalactic cosmic ray – High-energy particles from distant galaxies probing acceleration sites. Cosmic ray – high-energy radiation from outer space that may consist of protons or atomic nuclei.
Computational models Illustris project – Large-scale hydrodynamic simulation of galaxy formation. UniverseMachine – Empirical model for galaxy property evolution.
Galaxy structure relations De Vaucouleurs's law – Empirical profile for elliptical galaxy surface brightness. Sérsic profile – Generalizes de Vaucouleurs' law for galaxy morphologies. Jaffe profile – Analytic model for elliptical galaxy density profiles. M–sigma relation – Correlation between black hole mass and galaxy bulge velocity dispersion. Sigma-D relation – Links galaxy thickness to velocity dispersion. Virgocentric flow – Radial motions in Local Group galaxies.
Technical foundations
Methods and techniques
Observational astronomy – collection and analysis of electromagnetic radiation and other messengers from astronomical sources. Photometry – measurement of the brightness of astronomical sources in different wavelength bands. K correction – Adjusts galaxy magnitudes for cosmological redshift effects. Photographic magnitude – Historical magnitude system for archival comparisons. Astronomical spectroscopy – study of astronomy using spectroscopy to measure the spectrum of electromagnetic radiation emitted by celestial objects. Zeeman–Doppler imaging – Maps stellar surface magnetic fields spectropolarimetrically. Compton scattering – Dominant interaction of high-energy photons with electrons in hot plasmas. Doppler effect – change in frequency or wavelength of a wave in relation to an observer moving relative to the wave source. Differential Doppler effect – Fine velocity mapping in expanding supernova remnants. Astrometry – precise measurement of positions, motions, and distances of astronomical objects. Radiative transfer – modeling of the propagation of radiation through matter in astrophysical environments; description of the transport of radiation through a medium. Grey atmosphere – Simplified stellar atmosphere model assuming constant opacity. Optical depth (astrophysics) – Measure of photon mean free path in media. Source function – Ratio of emission to absorption coefficients in atmospheres. Magnetohydrodynamics – study of the dynamics of electrically conducting fluids such as plasmas in astrophysical contexts. Magnetogravity wave – Coupled Alfvén-gravity waves in stellar interiors. Wouthuysen–Field coupling – Enables 21cm absorption in early universe IGM. Numerical analysis and computer simulation in astrophysics – use of algorithms and simulations to model complex systems such as galaxy formation or stellar interiors. Press–Schechter formalism – Predicts dark matter halo mass function from Gaussian fluctuations. Sheth–Tormen approximation – Improves halo mass function predictions. Zeldovich approximation – First-order perturbation for large-scale structure growth. Gravitational-wave detection techniques – methods used to detect and analyze gravitational waves. Gravitational self-force – Backreaction on particles orbiting black holes. Regge–Wheeler–Zerilli equations – Perturbation equations for black hole spacetimes. Multi-messenger astronomy – coordinated use of electromagnetic radiation, gravitational waves, neutrinos, and cosmic rays to study astrophysical sources. Peryton (astronomy) – Fast radio burst-like signals from terrestrial interference, refining SETI searches.