Astronomy:Outline of astrophysics

Short description: Subfield of astronomy

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 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 – Fast radio burst-like signals from terrestrial interference, refining SETI searches.
• Hydrostatic equilibrium – balance between inward gravitational force and outward pressure in astrophysical objects such as stars.
• Jeans instability – criterion for gravitational collapse of a gas cloud.
  • Jeans's theorem – Phase-space density conservation in collisionless stellar dynamics.
  • Gravitational compression – Initial collapse trigger in star formation.
• Polarization – property of waves that describes the orientation of their oscillations.
  • Chandrasekhar polarization – Calculates scattering-induced polarization in stellar atmospheres.
• Standard candle – astronomical object with known luminosity used to measure distances in astronomy.
  • Phillips relationship – Standardizes Type Ia supernova light curves for cosmology.

Key models and profiles

• Dark matter halo and galaxy profiles
  • Navarro–Frenk–White profile – CDM simulation-derived dark matter halo profile.
  • Einasto profile – Dark matter halo density model fitting simulations and observations.
  • Osipkov–Merritt model – Anisotropic stellar distribution function for galaxies.
  • Plummer model – Softened potential for simulating star clusters.
• Relativistic astrophysics models
  • Nordtvedt effect – Lunar orbit test of strong equivalence principle.
  • Geodetic effect (aka De Sitter effect) – Relativistic clock rate variation in gravitational fields.
  • Vaidya metric – Describing radiating black hole spacetimes.
  • Weyl's postulate – Hypersurface-orthogonality in cosmological models.
  • White hole – Hypothetical time-reverse of black holes in general relativity.
  • Black hole greybody factors – Correct absorption/emission spectra of black holes beyond Hawking radiation idealization.
• Phenomenological models
  • Blast wave – Describes shock expansion in supernovae and gamma-ray bursts.
  • Ejecta – Material expelled in supernovae, shaping galactic chemical evolution.
  • Hubble–Reynolds law – Empirical relation for supernova remnant evolution.
  • Pulsed accretion – Episodic mass buildup in protostars driving outflows.
  • Superluminal motion – Apparent faster-than-light speeds in relativistic jets.
  • Relativistic beaming – Boosts emission in jets from black holes and pulsars.
  • Supra-arcade downflows – Plasma flows in post-flare arcades.
  • Gravitational lensing formalism – Mathematical framework mapping mass distributions via light deflection.
  • Virbhadra–Ellis lens equation – Exact gravitational lensing for strong fields.
  • Miyake event – Extreme solar proton events recorded in tree rings, informing cosmic ray history.

Instabilities, limits, and dynamics

• Quark matter – hypothetical phase of matter consisting primarily of quarks.
• Universe – all existing matter, energy, planets, stars, galaxies, and the space between them.
  • Angular momentum problem – Addresses conservation challenges in star and planet formation from collapsing clouds.
• B2FH paper – Seminal work on stellar nucleosynthesis processes producing elements beyond iron.

Plasma astrophysics

• Dusty plasma – Plasma with dust grains, common in stellar envelopes and nebulae.
• Plasma parameters – Dimensionless numbers characterizing astrophysical plasmas.
• Biermann battery – Mechanism generating magnetic fields in cosmic plasmas during structure formation.
• Firehose instability – Plasma instability in cosmic ray streaming regions.
• Magnetic helicity – Topological invariant conserved in MHD evolution of solar coronae.
• Magnetic mirror point – Reflection site for charged particles in magnetospheres.
• Woltjer's theorem – Conserves helicity in pulsar magnetospheres.
• Plasma physics – study of charged particles and fluids interacting with self‑consistent electric and magnetic fields.
  • Critical ionization velocity – Threshold limiting plasma ionization in cosmic shocks and aurorae.
  • Dissociative recombination – Key process in cooling primordial gas for star formation.
  • Hydrogen anion – Negative ion affecting opacity in cool stellar atmospheres.
  • Collision-induced absorption and emission – Spectral features in dense planetary and stellar atmospheres.

Stellar structure limits

• Chandrasekhar limit – Critical mass (~1.4 solar masses) determining white dwarf stability before supernova.
• Lane–Emden equation – Polytrope equation solving stellar structure.
• Polytrope – Self-similar stellar models approximating interiors.
• Schönberg–Chandrasekhar limit – Maximum hydrogen-depleted core mass in red giants.
• Tolman–Oppenheimer–Volkoff equation – Relativistic hydrostatic equilibrium for neutron stars.
• Tolman–Oppenheimer–Volkoff limit – Neutron star maximum mass (~2 solar masses).

Stellar dynamics and instabilities

• Chandrasekhar's variational principle – Optimizes stellar structure models under physical constraints.
• Chandrasekhar–Fermi method – Estimates interstellar magnetic fields from starlight polarization.
• Chandrasekhar–Friedman–Schutz instability – Instability in rotating relativistic stars leading to collapse.
• Chandrasekhar–Kendall function – Describes MHD equilibria in astrophysical jets and accretion disks.
• Chandrasekhar potential energy tensor – Tensor formalism for gravitational stability in self-gravitating systems.
• Darwin–Radau equation – Relates stellar density to moment of inertia for evolution tracking.
• Dirichlet's ellipsoidal problem – Equilibrium figures for self-gravitating rotating fluids.
• Jacobi ellipsoid – Triaxial equilibrium shape for rotating self-gravitating masses.
• Maclaurin spheroid – Oblate equilibrium figure for uniformly rotating fluids.
• Toomre's stability criterion – Prevents gravitational collapse in galactic disks.
• Bahcall–Wolf cusp – Predicted density profile of stars around supermassive black holes.
• Dynamical friction – Drag on massive objects moving through stellar/gas mediums.
• Mass segregation – Heavier stars sinking to cluster centers via dynamics.
• Mass deficit – Core collapse signature in globular clusters.
• Epicyclic frequency – Orbital oscillation frequency in galactic potentials.
• Rossby wave instability – Triggers coronal mass ejections in stellar dynamos.
• Richtmyer–Meshkov instability – Shock-driven mixing in supernova interiors.
• Shock waves in astrophysics – Accelerate cosmic rays in supernova remnants.
• Convective overturn – Global circulation in stellar convection zones affecting mixing and evolution.
• Champagne flow model – Explains star formation triggering in molecular clouds via supersonic outflows.
• Gas torus – Circumplanetary gas rings in planet formation models.
• Eddington number – Ratio gauging radiation pressure role in massive star stability.
• Entropy (astrophysics) – Measure of disorder in stellar interiors driving convection.
• Moment of inertia factor – Normalizes stellar rotation rates for evolution models.
• Photo-meson – Production process for high-energy neutrinos in cosmic rays.
• Gravitational scattering – Encounters shaping stellar velocities in clusters.

Stellar evolution

Stellar evolution – process by which a star changes over time.

• Hayashi track – Cooling path of pre-main-sequence stars on HR diagram.
• Applegate mechanism – Explains long-term brightness variations in binary stars via angular momentum redistribution.
• Chaotic rotation – Irregular tumbling of asteroids and moons due to impacts and resonances.
• Rotational Brownian motion – Random torques randomizing small body spins.

Instruments and observatories

• Optical and infrared telescopes
• Radio telescopes and interferometric arrays
• Space telescopes and space‑based observatories
• X-ray telescopes and gamma-ray telescopes
• Gravitational‑wave observatories
• Neutrino detectors
• Major observatories and facilities:
  • Hubble Space Telescope
  • James Webb Space Telescope
  • Very Large Telescope
  • Atacama Large Millimeter Array
  • Chandra X-ray Observatory
  • Fermi Gamma-ray Space Telescope
  • Calorimetric Electron Telescope – Instrument measuring cosmic ray electrons to probe astrophysical accelerators.
  • ARIANNA Experiment – Detector for ultra-high-energy neutrinos from cosmic sources like active galactic nuclei.
  • Compton telescope – Images gamma-ray sources like pulsars and black hole binaries.

Dark matter and gravity alternatives

• 2cDM model of dark matter – Two-component BSM theory proposing distinct particle species to address small-scale structure issues in cosmology, but requiring parameter fine-tuning.
• AQUAL – Modified gravity theory rivaling dark matter in explaining galactic dynamics.
• Dark fluid – Unified model combining dark matter and energy behaviors.
• Modified Newtonian dynamics – Empirical law replacing dark matter for galaxy rotations.
• Haloscope – Detector for axion dark matter conversion in magnetic fields.
• Bi-scalar tensor vector gravity – Alternative gravity theory addressing cosmic acceleration without dark energy.
• Gauge vector–tensor gravity – Modified gravity resolving galactic rotation anomalies.
• Scalar–tensor–vector gravity – MOND-like theory explaining galaxy dynamics.
• Tensor–vector–scalar gravity – Relativistic MOND variant fitting observations.
• Zeldovich equation of state – Degenerate matter model for compact objects.
• Oppenheimer–Snyder model – Dust collapse solution forming black holes.

History of astrophysics

• History of astrophysics
• History of astronomy
• History of spectroscopy
• History of stellar classification
• History of radio astronomy
• Timeline of gravitational physics and relativity
• Timeline of knowledge about galaxies, clusters of galaxies, and large-scale structure
• Timeline of white dwarfs, neutron stars, and supernovae
• History of physical cosmology

Astrophysics organizations

• International Astronomical Union
• American Astronomical Society
• Royal Astronomical Society
• European Southern Observatory
• Astrophysics Research Institute
• Jodrell Bank Centre for Astrophysics
• Max Planck Institute for Astrophysics

Astrophysics publications

• The Astrophysical Journal
• Monthly Notices of the Royal Astronomical Society
• Astronomy and Astrophysics
• Annual Review of Astronomy and Astrophysics
• Astronomy & Geophysics
• Astrophysics and Space Science
• Research in Astronomy and Astrophysics

Astrophysics awards

• Dannie Heineman Prize for Astrophysics
• Shaw Prize in Astronomy
• Gruber Prize in Cosmology
• Kavli Prize in Astrophysics
• Breakthrough Prize in Fundamental Physics (for astrophysics‑related work)

Persons influential in astrophysics

• Alastair G. W. Cameron
• Carl Sagan
• Riccardo Giacconi
• Viktor Ambartsumian
• Subrahmanyan Chandrasekhar
• Edwin Hubble
• Cecilia Payne-Gaposchkin
• Vera Rubin
• Stephen Hawking
• List of Russian astronomers and astrophysicists

Astrophysics scholars

• Angioletta Coradini
• Gustav Eberhard
• J. Marvin Herndon
• Ofer Lahav
• Donald Howard Menzel
• Carl Pennypacker

See also

• Outline of astronomy
• Outline of physics
• Outline of space science
• Chondritic uniform reservoir – Model for solar system bulk composition from meteoritic evidence.
• Compact objects – Densely packed stellar remnants including white dwarfs, neutron stars, and black holes.
• Direct numerical simulation – High-fidelity computational modeling of astrophysical fluids without subgrid approximations.
• Orbital mechanics – Application of mechanics to orbital trajectories of celestial bodies.

External links

• International Journal of Modern Physics D from World Scientific
• Cosmic Journey: A History of Scientific Cosmology from the American Institute of Physics
• Prof. Sir Harry Kroto, NL, Astrophysical Chemistry Lecture Series. 8 Freeview Lectures provided by the Vega Science Trust.
• Stanford Linear Accelerator Center
• Institute for Space Astrophysics and Cosmic Physics
• Astrophysical Journal
• Astronomy and Astrophysics
• List and directory of peer-reviewed Astronomy / Astrophysics Journals
• Master of Science in Astronomy and Astrophysics
• Ned Wright's Cosmology Tutorial, UCLA
• UNLV Astronomy & Astrophysics department