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Science Astronomy Galactic and extragalactic astronomy Basics

Basics

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

Andromeda–Milky Way collision

Predicted galactic collision

Region that has a no-return boundary

Isolated, small, and opaque nebula

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

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

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

Galaxy that does not belong to a larger cluster of galaxies

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 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 rotation curve

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

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

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

Kugelblitz (astrophysics)

Theorized concentration of light

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

Reflection nebula

Nebulosity in astronomy

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

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

Ultra-high-energy cosmic ray

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

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