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Science Astronomy Galactic and extragalactic astronomy

Galactic and extragalactic astronomy

Large-scale structures

Galaxy classification

Active galactic nucleus

Structure formed by diffuse material in orbital motion around a massive central body

Active galactic nucleus

Compact region at a galaxy's center with abnormally high luminosity

Andromeda–Milky Way collision

Predicted galactic collision

Barred spiral galaxy

Spiral galaxy with a central bar-shaped structure composed of stars

BL Lacertae object

Active galactic nucleus with rapid and large-amplitude flux variability and significant optical polarization and with spectrum dominated by a featureless nonthermal emission continuum

Region that has a no-return boundary

Very compact quasi-stellar radio source

Isolated, small, and opaque nebula

Brightest cluster galaxy

Brightest galaxy within a galaxy cluster

Dust floating in space

High-energy particle, mainly originating outside the Solar System

A possible non-random component of the peculiar velocity of galaxy clusters

A hypothesized galaxy with no, or very few, stars

Dark matter halo

A theoretical component of a galaxy that envelops the galactic disc and extends well beyond the edge of the visible galaxy

Type of interstellar cloud so dense that it obscures the visible wavelengths of light from objects behind it

Density wave theory

Theory to explain the spiral arm structure of spiral galaxies

Dwarf elliptical galaxy

Small galaxy composed of up to several billion stars

Eddington luminosity

Maximum luminosity of a body in hydrostatic equilibrium

Elliptical galaxy

Galaxy having an approximately ellipsoidal shape and a smooth, nearly featureless brightness profile

Emission nebula

Cloud of ionized gas emitting light of various colors

A region in spacetime from which nothing can escape

Extragalactic astronomy

Astronomy dealing with objects outside the Milky Way

Faber–Jackson relation

Empirical power-law relation between the luminosity and the central stellar velocity dispersion of elliptical galaxy

Galaxy that does not belong to a larger cluster of galaxies

Flocculent spiral galaxy

Patchy galaxy with discontinuous spiral arms

Galactic astronomy

Study of the Milky Way galaxy and its contents

Tightly packed group of stars within a larger formation

Component of a galaxy

Plane on which the majority of a disk-shaped galaxy's mass lies

Tidal force experienced by objects subject to the gravitational field of a galaxy

Gravitationally bound astronomical structure

Structure made up of a gravitationally-bound aggregation of hundreds of galaxies

Galaxy filament

Largest structures in the universe, made of galaxies

Galaxy formation and evolution

Processes that formed a heterogeneous universe from a homogeneous beginning, the formation of the first galaxies, the way galaxies change over time

Structure made up of a gravitationally-bound aggregation of about 50 or fewer galaxies; is smaller than a galaxy cluster

Galaxy groups and clusters

Largest known gravitationally bound object in universe; aggregation of galaxies

Merger whereby at least two galaxies collide

Galaxy morphological classification

System for categorizing galaxies based on appearance

Galaxy rotation curve

Plot of the orbital speeds of visible stars or gas in that galaxy versus their radial distance from that galaxy’s center

Grand design spiral galaxy

Galaxy with prominent and well-defined spiral arms,

Gravitational lens

Light bending by mass between source and observer

Interstellar cloud composed of neutral atomic hydrogen

Large, low-density interstellar cloud of partially ionized gas

High-velocity cloud

Molecular cloud with speed greater than 90 km/s

Hubble sequence

Galaxy morphological classification scheme invented by Edwin Hubble

Interacting galaxy

Galaxies whose gravitational fields result in the disturbance of one another.

Intergalactic dust

Cosmic dust in between galaxies in intergalactic space

Interstellar cloud

Accumulation of gas, plasma, and dust in space

Interstellar ice

Ice that forms in the interstellar medium

Interstellar medium

Matter and radiation in the space between the star systems in a galaxy

Intracluster medium

Superheated plasma that permeates a galaxy cluster

Irregular galaxy

Galaxy not having a distinct regular shape

Kugelblitz (astrophysics)

Theorized concentration of light

Lenticular galaxy

Type of galaxy intermediate between an elliptical and a spiral galaxy

Low surface brightness galaxy

A galaxy which is less bright than the ambient night sky

Low-ionization nuclear emission-line region

Type of galactic nucleus

Luminous infrared galaxy

Galaxy with a high luminosity

Lyman-alpha emitter

Lyman-alpha forest

Astronomical spectroscopic term

Magellanic spiral

Type of dwarf galaxy with one spiral arm

Micro black hole

Hypothetical black holes of very small size

Molecular cloud

Type of interstellar cloud

Interstellar cloud of dust, hydrogen, helium and other ionized gases

Void between celestial bodies

Peculiar galaxy

Galaxy of unusual size, shape, or composition; between five and ten percent of known galaxies are categorized as peculiar

Active galactic nucleus containing a supermassive black hole

Type of active galaxy that is very luminous at radio wavelengths

Reflection nebula

Nebulosity in astronomy

A galaxy with a circle-like appearance

Satellite galaxy

Galaxy that orbits a larger galaxy due to gravitational attraction

Schwarzschild radius

Distance from a massive body where the escape velocity equals the speed of light

A class of active galaxies with very bright nuclei

Galaxy having a number of arms of younger stars

Astronomical theory that star formation propagates via the action of shock waves produced by stellar winds and supernovae traversing the gas that composes the interstellar medium

Strong gravitational lensing

Effect strong enough to produce multiple images, arcs, or even Einstein rings

Cavity hundreds of light years across created by strong stellar winds in a galaxy

Large group of smaller galaxy clusters or galaxy groups

Supermassive black hole

Largest type of black hole

Structural component of some galaxies

Structural component of galaxies

Tully–Fisher relation

Trend in astronomy

Galaxy morphology classification

Ultra-high-energy cosmic ray

A cosmic-ray particle with a kinetic energy greater than 1018 eV

Unbarred spiral galaxy

Type of spiral galaxy without a central bar

Void (astronomy)

Vast empty spaces between filaments with few or no galaxies

Warm–hot intergalactic medium

Plasma that cosmologists believe exists between galaxies

Weak gravitational lensing

Gravitational deflection of light without creating noticeable extra images

Hypothetical topological feature of spacetime