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Astronomy

Astronomy basics

Observational astronomy

Astronomical objects

Celestial mechanics

Celestial sphere

Planetary science

Stellar astronomy

Galactic and extragalactic astronomy

Physical cosmology

Interstellar object passed near Earth in 2017

Large asteroid of the main asteroid belt

Large, ringed 200km centaur/comet with 50-year orbit

Interstellar comet passing through the Solar System, discovered in 2019

Astronomical survey of the whole sky in the infrared

Brightest quasar from Earth located in the constellation Virgo

Second-largest asteroid of the main asteroid belt

Globular cluster in the constellation Tucana

486958 Arrokoth

Kuiper belt object

Hot Jupiter orbiting 51 Pegasi

Extrasolar planet in the constellation Cancer

Absolute magnitude

Measure of the luminosity of celestial objects

Accelerating expansion of the universe

Cosmological phenomenon

Accretion (astrophysics)

Accumulation of particles into a massive object by gravitationally attracting more matter

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

Star in the constellation Eridanus

Star in the constellation Crux

Active galactic nucleus

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

Time of the day between noon and evening

Age of the universe

Time elapsed since the Big Bang

Air mass (astronomy)

The amount of air seen through in astronomical observations

Faint emission of light by a planetary atmosphere

Ratio of reflected radiation to incident radiation

Star in the constellation Taurus

Family of programming languages

Star system in the Centaurus constellation

Alpher–Bethe–Gamow paper

Scientific theory

Brightest star in the constellation Aquila

Amateur astronomy

Hobby of watching the sky and stars

Andromeda (constellation)

Constellation in the northern celestial hemisphere

Andromeda Galaxy

Barred spiral galaxy in the Local Group

Andromeda–Milky Way collision

Predicted galactic collision

Angular diameter

How large a sphere or circle appears

Angular resolution

Ability of any image-forming device to distinguish small details of an object

Red supergiant star in the constellation Scorpius

Antennae Galaxies

Interacting galaxy in the constellation Corvus

Anthropic principle

Hypothesis about sapient life and the universe

Constellation in the Southern Celestial Hemisphere

Apparent magnitude

Brightness of a celestial object observed from the Earth

Either of two extreme points in a celestial object's orbit

Constellation in the southern celestial hemisphere

Aquarius (constellation)

Zodiac constellation straddling the celestial equator

Aquila (constellation)

Constellation on the celestial equator

Ara (constellation)

Constellation in the southern celestial hemisphere

Brightest star in the constellation Boötes

Obsolete Southern constellation

Fourth-largest moon of Uranus

Aries (constellation)

Constellation in the zodiac

Luminous infrared galaxy in the constellation Serpens

Asterism (astronomy)

Pattern of stars recognized on Earth's night sky

Minor planet that is not a comet

The circumstellar disk (accumulation of matter) in an orbit between those of Mars and Jupiter

Asteroseismology

Study of oscillations in stars

Science concerned with life in the universe

The study of molecules in the Universe and their reactions

Branch of astronomy involving positioning and movements of celestial bodies

One who studies celestial bodies and space

Astronomical coordinate systems

System for specifying positions of celestial objects

Astronomical object

Natural physical entity in space

Astronomical radio source

Object in outer space that emits strong radio waves

Astronomical seeing

Amount of apparent blurring and twinkling of astronomical objects due to atmospherical effects

Astronomical spectroscopy

Science of temporal, spatial, and spectral distributions of radiation

Astronomical transit

Term in astronomy

Scientific study of celestial objects and phenomena

Astrophotography

Astronomical imaging

Astrophysical maser

Naturally occurring source of stimulated spectral line emission, typically in the microwave portion of the electromagnetic spectrum

Astrophysical X-ray source

Astronomical object emitting X-rays

Branch of astronomy

Astrophysics Data System

Digital Library portal operated by the Smithsonian

Asymptotic giant branch

Stars powered by fusion of hydrogen and helium in shell with an inactive core of carbon and oxygen

Layer of gases surrounding an astronomical body held by gravity

Atmosphere of Jupiter

Layer of gases surrounding the planet Jupiter

Atmosphere of Mars

Layer of gases surrounding planet Mars

Atmosphere of Mercury

Composition and properties of the atmosphere of the innermost planet of the Solar System

Atmosphere of Pluto

Layer of gases surrounding the dwarf planet Pluto

Atmosphere of Uranus

Layer of gases surrounding the planet Uranus

Atmosphere of Venus

Dense and hot, the atmosphere of planet Venus is mostly CO2 with clouds of sulfuric acid

Constellation in the northern celestial hemisphere

Axial precession

Gravity-induced, slow, and continuous change in the orientation of an astronomical body's rotational axis

Angle between the rotational axis and orbital axis of a body

B-type star with distinctive forbidden neutral or low ionisation emission lines in its spectrum

Red dwarf star about six light-years from Earth in the constellation Ophiuchus

Barred spiral galaxy

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

Barycenter (astronomy)

Center of mass of multiple bodies orbiting each other

Hypothesized processes that could produce baryonic asymmetry, favoring matter (baryons) over antimatter (antibaryons)

Baryon acoustic oscillations

Fluctuations in the density of the visible baryonic matter of the universe, caused by acoustic density waves in the primordial plasma of the early universe

In astronomy, a B-type star with emission lines

Beehive Cluster

Open cluster in the constellation Cancer

Atmospheric phenomenon

Star system in the constellation of Centaurus

Second brightest star in the southern constellation of Pictor

Red supergiant star in the constellation of Orion

Bi-elliptic transfer

Maneuver that moves a spacecraft from one orbit to another

Cosmological model

Big Bang nucleosynthesis

The earliest production of nuclei other than those of the lightest isotope of hydrogen during the early phases of the Universe

Hypothetical scenario for the ultimate fate of the universe

Pattern of seven bright stars in the constellation Ursa Major

Cosmological model based on an exponentially increasing rate of expansion

Pulsar with a binary companion, often a white dwarf or neutron star

Star system consisting of two stars

Active galaxy in the constellation Lacerta

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

Cold stellar remnant

Region that has a no-return boundary

Very compact quasi-stellar radio source

Giant star of early spectral type

Period of twilight in the morning or evening

A main sequence star that is more luminous and bluer than expected

Blue supergiant

Isolated, small, and opaque nebula

Constellation in the northern celestial hemisphere

An enormous, approximately spherical region of space, containing very few galaxies

A scale of night sky brightness.

BOSS Great Wall

The largest known galaxy wall

Brightest cluster galaxy

Brightest galaxy within a galaxy cluster

Brightness temperature

Temperature associated with the measured intensity and frequency

Brocchi's Cluster

Asterism of 10 stars in the constellation Vulpecula

Type of substellar object more massive than a planet

Two colliding clusters of galaxies in constellation Carina

Constellation in the southern celestial hemisphere

Callisto (moon)

Second-largest moon of Jupiter

Constellation in the northern celestial hemisphere

Cancer (constellation)

Zodiac constellation in the northern celestial hemisphere

Constellation in the northern celestial hemisphere

Constellation in the southern celestial hemisphere

Constellation straddling the celestial equator

Star in the constellation of Carina

Brightest star in the constellation Auriga

Zodiac constellation in the southern celestial hemisphere

Hypothetical type of planet that contains more carbon than oxygen

Star whose atmosphere contains more carbon than oxygen

Carbon-burning process

Nuclear fusion process in the cores of massive stars, combining carbon nuclei into heavier elements

Carina (constellation)

Constellation in the southern celestial hemisphere

H II region in the constellation Carina

Carina–Sagittarius Arm

Spiral arm of the Milky Way Galaxy

Cartwheel Galaxy

A lenticular galaxy and ring galaxy in the constellation Sculptor

Cassiopeia (constellation)

Constellation in the northern celestial hemisphere

Supernova remnant in the constellation Cassiopeia

Star in the constellation Gemini

Cataclysmic variable star

Stars which irregularly increase in brightness by a large factor, then drop back down to a quiescent state

Cat's Eye Nebula

Planetary nebula in the constellation Draco

Celestial cartography

Part of astronomy concerned with mapping of stars

Celestial equator

Projection of the Earth's equator out into space

Celestial mechanics

Branch of astronomy

Celestial sphere

Imaginary sphere of arbitrarily large radius, concentric with the observer

Centaur (small Solar System body)

Solar System body

Constellation in the southern celestial hemisphere

Radio galaxy in the Constellation Centaurus

Centaurus A/M83 Group

Group of galaxies in the constellations Centaurus, Hydra and Virgo

Cepheid variable

Type of variable star

Cepheus (constellation)

Constellation in the northern celestial hemisphere

Ceres (dwarf planet)

Largest asteroid and dwarf planet

Constellation straddling the celestial equator

Constellation in the southern celestial hemisphere

Chandrasekhar limit

Maximum mass of a stable white dwarf star

Largest natural satellite of Pluto

Chemically peculiar star

Stars with distinctly unusual metal abundances

A layer in the Sun's atmosphere above the photosphere

Chronology of the universe

History and future of the universe

Chthonian planet

Hypothetical class of celestial objects resulting from the stripping away of a gas giant's hydrogen and helium atmosphere and outer layers

Constellation in the southern celestial hemisphere

Circumstellar disc

Torus, pancake or ring-shaped accumulation of matter in orbit around a star

Classical Cepheid variable

Type of variable star

Clearing the neighbourhood

Criterion for a celestial body to be considered a planet

Climate of Uranus

Anomaly in the cosmic microwave background

Catalysed fusion reactions by which stars convert hydrogen to helium

Coalsack Nebula

Dark nebula in the constellation Crux

Columba (constellation)

Constellation in the southern celestial hemisphere

Constellation in the northern hemisphere

Cluster of galaxies in the constellation Coma Berenices

Comet Hale–Bopp

Long-Period Comet

Comet Hyakutake

Comet that passed close to Earth in March 1996

Comet Shoemaker–Levy 9

Comet that collided with Jupiter

Common envelope

Community of Metros

Rapid transit benchmarking organization

Comoving and proper distances

Measurement of distance

Classification in astronomy

Computational astrophysics

Methods and computing tools developed and used in astrophysics research

Group of stars forming a pattern on the celestial sphere

Convection zone

(of a star) layer which is unstable to convection. Energy is primarily or partially transported by convection in such a region

Co-orbital configuration

Configuration of two or more astronomical objects

Coreless planet

Extrasolar terrestrial planet without a core

Corona Australis

Constellation in the southern celestial hemisphere

Corona Borealis

Constellation in the northern celestial hemisphere

Coronal mass ejection

Ejecta from the Sun's corona

Corvus (constellation)

Constellation in the Southern Celestial Hemisphere

Cosmic distance ladder

Succession of methods by which astronomers determine the distances to celestial objects

Dust floating in space

Cosmic inflation

Theory of rapid universe expansion

Cosmic microwave background

Trace radiation from the early universe

High-energy particle, mainly originating outside the Solar System

Study of the chemical composition of matter in the universe and the processes that led to those compositions

Cosmological constant

Value representing energy density of space

Cosmological horizon

Horizon appearing on a cosmological scale

The scientific study of the origin, evolution, and eventual fate of the universe

Supernova remnant in the constellation Taurus

Pulsar in the constellation Taurus

Crater (constellation)

Constellation in the southern celestial hemisphere

Linux distribution

Variable star in the constellation Leo

Cosmological model involving repetitions of Big Bangs followed by Big Crunches

Cygnus (constellation)

Constellation in the northern celestial hemisphere

Supernova remnant in the constellation Cygnus

Galactic X-ray source in the constellation Cygnus that is very likely a black hole

Unknown property in cosmology that causes the expansion of the universe to accelerate.

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

A hypothesized galaxy with no, or very few, stars

Hypothetical invisible cosmic material

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

Time that marks the beginning of the twilight before sunrise

Combination of all direct and indirect sunlight outdoors during the daytime

Daytime Protocol

Computer text protocol for viewing clock time

Circumstellar disk of dust and debris in orbit around a star

Astronomical coordinate analogous to latitude

Definition of planet

History of the word "planet" and its definition

The smaller, outer, moon of Mars

Constellation in the northern celestial hemisphere

Star in the constellation Cygnus

Density wave theory

Theory to explain the spiral arm structure of spiral galaxies

Dipole repeller

A center of effective repulsion in the large-scale flow of galaxies in the neighborhood of the Milky Way

Discovery of cosmic microwave background radiation

Aspect of the history of modern physical cosmology

Constellation in the southern sky

Science fiction novel by Robert A. Heinlein

Draco (constellation)

Constellation in the northern celestial hemisphere

Probabilistic argument to estimate the number of alien civilizations in the galaxy

Dumbbell Nebula

Planetary nebula in the constellation Vulpecula

Darkest stage of twilight, at end of astronomical twilight after sunset and just before night

Dwarf elliptical galaxy

Small galaxy composed of up to several billion stars

Small planetary-mass object

Dysnomia (moon)

Open cluster in the constellation Serpens

Third planet from the Sun

Planet with environmental conditions similar to those on Earth

Earthlight (astronomy)

Astronomical phenomenon

Trajectory of Earth around the Sun

Shadow that the Earth casts on its own atmosphere

Astronomical event where one body is hidden by another

Intervals of eclipses

Apparent path of the Sun on the celestial sphere

Eddington luminosity

Maximum luminosity of a body in hydrostatic equilibrium

Effective temperature

Estimated temperature of an astronomical body

Electroweak epoch

Period in the evolution of the early universe in which electroweak symmetry is not yet broken

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

Natural satellite (moon) orbiting Saturn

Epoch (astronomy)

Moment in time used as a reference point in astronomy

Epsilon Canis Majoris

Star in the constellation Canis Major

Epsilon Eridani

Star in the constellation Eridanus

Equatorial coordinate system

Celestial coordinate system used to specify the positions of celestial objects

Semi-annual astronomical event where the Sun is directly above the Earth's equator

Equinox (celestial coordinates)

Astronomical location

Japanese nanosatellite

Eridanus (constellation)

Constellation in the southern hemisphere

Eris (dwarf planet)

Escape velocity

Concept in celestial mechanics

Stellar system in the constellation Carina

Smallest Galilean moon of Jupiter

Period of the day between afternoon and nighttime

A region in spacetime from which nothing can escape

Moon beyond the Solar System

Planet outside the Solar System

Hypothetical compact star composed of exotic matter

A theoretical type of exotic star.

Expansion of the universe

Increase in distance between parts of the universe over time

Extinction (astronomy)

In astronomy, the absorption and scattering of electromagnetic radiation by dust and gas between an emitting astronomical object and the observer

Extragalactic astronomy

Astronomy dealing with objects outside the Milky Way

Extraterrestrial intelligence

Intelligent extraterrestrial life

Extraterrestrial life

Hypothetical life that does not originate on Earth

Extraterrestrial vortex

Vortex on non-Earth planets with atmospheres

Faber–Jackson relation

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

Far side of the Moon

Hemisphere of the Moon that always faces away from Earth

Fast radio burst

Astronomical high energy transient pulse

Discrepancy of the lack of evidence for alien life despite its apparent likelihood

Galaxy that does not belong to a larger cluster of galaxies

Type of variable star that can undergo unpredictable dramatic increases in brightness for a few minutes

Flatness problem

Cosmological fine-tuning problem

Flocculent spiral galaxy

Patchy galaxy with discontinuous spiral arms

Star in the constellation Piscis Austrinus

Forbidden mechanism

Spectral line associated with absorption or emission of light by atomic nuclei, atoms, or molecules

Formation and evolution of the Solar System

Constellation in the southern celestial hemisphere

Galaxy cluster in the constellation Fornax

Orbit for an artificial satellite in which natural drifting due to the central body's shape has been minimized by careful selection of the orbital parameters

Lunar phase: completely illuminated disc

Future of Earth

Long term extrapolated geological and biological changes

Galactic astronomy

Study of the Milky Way galaxy and its contents

Tightly packed group of stars within a larger formation

Galactic Center

Rotational center of the Milky Way galaxy

Galactic coordinate system

A celestial coordinate system in spherical coordinates, with the Sun as its center

Galactic habitable zone

Region of a galaxy in which life might most likely develop

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

Four largest moons of Jupiter

Gamma Cassiopeiae

Star in the constellation Cassiopeia

Gamma-ray astronomy

Observational astronomy performed with gamma rays

Gamma-ray burst

Flashes of gamma rays from distant galaxies

Gamma-ray burst emission mechanisms

Gamma-ray burst progenitors

Types of celestial objects that can emit gamma-ray bursts

Ganymede (moon)

Largest moon of Jupiter and in the Solar System

Giant planet mostly made of light elements

Interstellar cloud within the Milky Way Galaxy

Faint brightening of the night sky in the region of the antisolar point

Gemini (constellation)

Zodiac constellation in the northern hemisphere

Geological history of Mars

Physical evolution of the planet Mars

Geology of Mars

Scientific study of the surface, crust, and interior of the planet Mars

Geology of Mercury

Geologic structure and composition of planet Mercury

Geology of the Moon

Structure and composition of the Moon

Geology of Venus

Geological structure and composition of the second planet from the Sun

Geometric albedo

Geostationary orbit

Circular orbit above the Earth's equator and following the direction of the Earth's rotation

Geosynchronous orbit

Orbit keeping the satellite at a fixed longitude above the equator

Planet much larger than the Earth

Type of star, larger and brighter than the Sun

Giant-impact hypothesis

Theory of the formation of the Moon

Possible extrasolar planet in the constellation Libra

Globular cluster

Spherical collection of stars

Golden hour (photography)

First and last hour of sunlight during the day

Gonggong (dwarf planet)

Dwarf planet in the scattered-disc

A partial ring of stars in the Milky Way galaxy

Grand design spiral galaxy

Galaxy with prominent and well-defined spiral arms,

Grand unification epoch

Theorized events that take place immediately after the Big Bang and validate some ideas around baryogenesis

Graveyard orbit

Supersynchronous orbit where spacecraft are intentionally placed at the end of their operational life

Gravitational collapse

Contraction of an astronomical object due to the influence of its own gravity

Gravitational lens

Light bending by mass between source and observer

Gravitational-wave astronomy

Type of astronomy involving observation of gravitational waves

Space navigation technique

Great Attractor

An apparent gravitational anomaly at the center of the local Laniakea Supercluster

Great Dark Spot

Large storm in Neptune's atmosphere

Whatever prevents interstellar civilisations from arising from non-living matter

A persistent storm in the atmosphere of Jupiter

Grus (constellation)

Constellation in the southern celestial hemisphere

Gravitational wave signal detected by the LIGO observatory on 17 August 2017

Interstellar cloud composed of neutral atomic hydrogen

Large, low-density interstellar cloud of partially ionized gas

Orbits where planets may have liquid water

Period in the evolution of the early universe

Short-period comet visible every 75–77 years

Periodic, three-dimensional orbit

Luminosity-temperature relationship obeyed by infant stars

Extrasolar planet in the constellation Vulpecula

Extrasolar planet

Heat Death of the Universe

Topics referred to by the same term

Heliosphere (science fiction convention)

Brief thermal runaway nuclear fusion in the core of low mass stars

Herbig Ae/Be star

Young star of spectral types A and B

Hercules (constellation)

Constellation in the northern celestial hemisphere

Hertzsprung–Russell diagram

A scatter plot of stars showing the relationship between the stars' absolute magnitudes or luminosities versus their stellar classifications

High-energy astronomy

Study of astronomical objects that release ionizing radiation of highly energetic wavelengths

High-velocity cloud

Molecular cloud with speed greater than 90 km/s

Non-typical galaxy in the constellation Serpens

Hohmann transfer orbit

Elliptical orbit used to transfer between two orbits of different altitudes, in the same plane

Apparent curve that separates earth from sky

Horizon problem

Cosmological fine-tuning problem

Horizontal branch

Stars powered by helium fusion

Horologium (constellation)

Constellation in the southern celestial hemisphere

Horsehead Nebula

Dark nebula in the constellation Orion

Horseshoe orbit

Type of co-orbital motion of a small orbiting body relative to a larger orbiting body

Class of high mass planets orbiting close to a star

Coordinates used in the equatorial coordinate system

Hubble Deep Field

Multiple exposure image of deep space in the constellation Ursa Major

Hubble sequence

Galaxy morphological classification scheme invented by Edwin Hubble

Hubble Ultra-Deep Field

Image of a small region of space in the constellation Fornax, containing ~10,000 galaxies

Region of the observable universe

Observation in physical cosmology

Large quasar group

Hyades (star cluster)

Open cluster in the constellation Taurus

Hydra (constellation)

Constellation straddling the celestial equator

Constellation in the southern celestial hemisphere

Rare star with tremendous luminosity and high rates of mass loss by stellar winds

A supernova that ejects a large mass at unusually high velocity

Hypothetical types of biochemistry

Possible alternative biochemicals used by life forms

IAU definition of planet

Formal definition of a planet in the context of the Solar System as ratified by the IAU in 2006

Supergiant elliptical galaxy in the constellation Virgo

IC 342/Maffei Group

Group of galaxies

Giant planet primarily consisting compounds with freezing points exceeding 100°K

Collision of two astronomical objects

Indus (constellation)

Constellation in the southern celestial hemisphere

Infrared astronomy

Observational astronomy of emissions over the wavelength band 0.75 to 300 micrometers

Initial mass function

Empirical function that describes the initial distribution of masses for a population of stars

Instability strip

Stellar classification

Interacting galaxy

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

Intergalactic dust

Cosmic dust in between galaxies in intergalactic space

Intergalactic star

Star not gravitationally bound to any galaxy

Internal structure of the Moon

Overview of the internal structure of the Moon

Interplanetary dust cloud

Cosmic dust in the space between the planets of the solar system

Interplanetary medium

Material which fills the Solar System

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

Interstellar object

Astronomical object not gravitationally bound to a star

Intracluster medium

Superheated plasma that permeates a galaxy cluster

Innermost of the four Galilean moons of Jupiter

Extrasolar terrestrial planet

Irregular galaxy

Galaxy not having a distinct regular shape

Jeans instability

Mechanism by which the collapse of interstellar gas clouds causes star formation

Fifth planet from the Sun

Asteroid sharing the orbit of Jupiter

Jupiter's North Pole

Exoplanet orbiting the red dwarf K2-18

Terrestrial exoplanet orbiting Kepler-186

Exoplanet orbiting around Kepler-22

Extrasolar planet

Extrasolar planet

Kepler's laws of planetary motion

Scientific laws describing motion of planets around the Sun

Kepler's Supernova

Supernova visible from Earth in the 17th century

Supernova formed from a neutron star merger

Kreutz sungrazer

Family of comets

Kugelblitz (astrophysics)

Theorized concentration of light

Area of the Solar System beyond the planets, comprising small bodies

Constellation in the northern celestial hemisphere

Emission nebula in Sagittarius

One of five positions in an orbital configuration of two large bodies where a small object can maintain a stable relative position

Hydrocarbon lakes on Titan, a moon of Saturn

Lambda-CDM model

Model of big-bang cosmology

Laniakea Supercluster

Galaxy supercluster

Large Magellanic Cloud

Satellite galaxy of the Milky Way

Star in the constellation Sagittarius

Lenticular galaxy

Type of galaxy intermediate between an elliptical and a spiral galaxy

Leo (constellation)

Zodiac constellation passing through the celestial equator

Constellation in the northern celestial hemisphere

Period in the evolution of the early universe

Lepus (constellation)

Constellation in the southern celestial hemisphere

Libra (constellation)

Zodiac constellation in the southern celestial hemisphere

Apparent oscillation of a minor body seen from the major body it orbits

Scientific assessments on the microbial habitability of Mars

Graph of light intensity of a celestial object or region, as a function of time

Lissajous orbit

Quasi-periodic orbital trajectory

List of Chinese star names

List of interstellar and circumstellar molecules

Molecules detected in space

List of the most distant astronomical objects

Cavity in the interstellar medium which contains the Local Interstellar Cloud

Group of galaxies that includes the Milky Way

Large, comparatively empty region of space

Local Interstellar Cloud

Interstellar cloud in the Milky Way Galaxy

Nearby extragalactic region of space

Empty region of space adjacent to the Local Group of galaxies.

Location of Earth

Location of the Earth in the Universe

Low Earth orbit

Orbit around Earth with an altitude between 160 and 2,000 kilometers

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

Measurement of radiant electromagnetic power emitted by an object

Luminosity distance

Astronomical measurand

Luminous blue variable

Luminous infrared galaxy

Galaxy with a high luminosity

Natural phenomenon wherein the Earth casts a shadow on the Moon

The shape of the Moon's directly sunlit portion as viewed from Earth

Lunar south pole

Southernmost point on the Moon

Lupus (constellation)

Constellation in the southern celestial hemisphere

Lyman-alpha emitter

Lyman-alpha forest

Astronomical spectroscopic term

Lynx (constellation)

Constellation in the northern celestial hemisphere

Ultraviolet radiometer on the Proba-2 spacecraft

Galaxy group in Ursa Major and Camelopardalis

Magellanic Clouds

Two dwarf galaxies orbiting the Milky Way

Magellanic spiral

Type of dwarf galaxy with one spiral arm

Magellanic Stream

High-velocity cloud of gas connecting the Large and the Small Magellanic Clouds

Type of neutron star with a strong magnetic field

Region around an astronomical object in which its magnetic field affects charged particles

Magnetosphere of Jupiter

Cavity created in the solar wind

Magnetosphere of Saturn

Cavity in the solar wind the sixth planet creates

Magnitude (astronomy)

Logarithmic measure of the brightness of an astronomical object

A continuous band of stars that appears on plots of stellar color versus brightness

Dwarf planet in the Outer Solar System

The equinox on the Earth when the Sun appears to leave the southern hemisphere and cross the celestial equator

Seyfert galaxy in the constellation Ursa Major

Blazar located in the constellation Ursa Major

Galaxy with a spectrum extending to the highest gamma rays.

MaRS Discovery District

Scientific research centre in Toronto

Martian polar ice caps

Polar water ice deposits on Mars

Mass–luminosity relation

Equation in stellar astrophysics

Type of astrophysical maser with large isotropic luminosity

Mensa (constellation)

Constellation in the southern celestial hemisphere

Mercury (planet)

First planet from the Sun

Meridian (astronomy)

Great circle passing through the celestial poles, the zenith, and the nadir of a particular location

Spiral galaxy in the constellation Canes Venatici

Globular cluster in the constellation Hercules

Globular cluster in the constellation Pegasus

Globular cluster in Sagittarius

Globular cluster in Scorpius

Elliptical galaxy in the constellation Virgo

Open star cluster in the constellation of Scorpius

Barred spiral galaxy in the constellation Cetus

Spiral galaxy in the constellation Ursa Major

A starburst galaxy in the constellation Ursa Major

Barred spiral galaxy in the constellation Hydra

Elliptical galaxy in the Virgo Galaxy Cluster

Astronomical objects catalogued by Charles Messier

Relative abundance of heavy elements in a star or other astronomical object

Celestial event caused by streams of meteoroids entering Earth's atmosphere

Sand- to boulder-sized particle of debris in the Solar System

Methods of detecting exoplanets

Micro black hole

Hypothetical black holes of very small size

Minor constellation in the southern celestial hemisphere

Transition time from one day to the next

Natural phenomenon when daylight lasts for a whole day

Galaxy containing the Solar System

Star in the constellation Crux

Astronomical object in direct orbit around the Sun that isn't a planet or a comet

Red-giant star Omicron Ceti

Type of variable star

Missing baryon problem

Discrepency between observed and predicted amounts of ordinary matter

Molecular cloud

Type of interstellar cloud

Type of high-latitude satellite orbit

Faint constellation on the celestial equator

Natural satellite orbiting Earth

Moons of Haumea

Natural satellites orbiting dwarf planet Haumea

Moons of Jupiter

Natural satellites of the planet Jupiter

Natural satellites orbiting Mars

Moons of Neptune

Natural satellites of the planet Neptune

Natural satellite orbiting Pluto

Moons of Saturn

Natural satellites of the planet Saturn

Moons of Uranus

Natural satellites of the planet Uranus

Period of time from midnight or sunrise to noon

Period of time from midnight or sunrise to noon

Hypothetical group of multiple universes

Constellation in the southern celestial hemisphere

Direction pointing directly below a particular location

NASA/IPAC Extragalactic Database

Astronomical database

Natural satellite

Astronomical body that orbits a planet

Near side of the Moon

Hemisphere of the Moon facing the Earth

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

Nebular hypothesis

Astronomical theory that the Solar System formed from nebulous material

Regional-scale underwater ocean observatory running deep-water experiments

Neutrino astronomy

Observational astronomy that benefits from the direct, or indirect, detection of neutrinos

Collapsed core of a massive star

New General Catalogue

Astronomical catalogue of deep sky objects

Phase of the Moon

Seyfert galaxy in the constellation Perseus

Galaxy in the constellation Canes Venatici

Barred spiral galaxy in the constellation Centaurus

Seyfert galaxy in the constellation Boötes

Bipolar planetary nebula in the constellation Scorpius

Galaxy in the constellations Cepheus & Cygnus

Planetary nebula in the constellation Cygnus

Astrophysical model of planetary migration in the Solar System

Period of darkness

Appearance of the sky in a clear night

12 o'clock in the daytime

Norma (constellation)

Constellation in the southern celestial hemisphere

Spiral arm of the Milky Way Galaxy

Nuclear explosion in a white dwarf star

Maneuver in which a spacecraft falls into a gravitational well, and then accelerates when its fall reaches maximum speed

Observable universe

All of space observable from the Earth at the present

Observational cosmology

Location used for observing terrestrial or celestial events

Constellation in the southern celestial hemisphere, containing the south celestial pole

Martian volcano, tallest point on Mars

Globular cluster in the constellation Centaurus

Emission nebula in Sagittarius

Distant planetesimals in the Solar System

Group of "sibling" stars that are loosely gravitationally bound to one another

Zodiac constellation straddling the celestial equator

Orbit of the Moon

The Moon's circuit around the Earth

Orbital eccentricity

Amount by which an orbit deviates from a perfect circle

Orbital elements

Parameters that uniquely identify a specific orbit

Orbital inclination

Angle between a reference plane and the plane of an orbit

Orbital mechanics

Field of classical mechanics concerned with the motion of spacecraft

Orbital resonance

Regular and periodic mutual gravitational influence of orbiting bodies

Orbital station-keeping

Maneuvers made to maintain a particular orbit

Origin of the Moon

How the Earth's moon was formed

Orion (constellation)

Constellation straddling the celestial equator

Minor spiral arm of the Milky Way galaxy; contains the Solar System

Diffuse nebula in the constellation Orion

Asterism of three stars in the constellation Orion

Void between celestial bodies

Pair-instability supernova

Type of high-energy supernova in very large stars

Particle horizon

The maximum distance from which light from particles could have traveled to the observer during the age of the universe

Pavo (constellation)

Constellation in the southern celestial hemisphere

Peculiar galaxy

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

Pegasus (constellation)

Constellation in the northern celestial hemisphere

Perseus (constellation)

Constellation in the northern celestial hemisphere

One of two major spiral arms of the Milky Way galaxy

Perseus Cluster

Galaxy cluster in the constellation Perseus

The larger, inner, moon of Mars

Phoenix (constellation)

Minor constellation in the southern sky

Photometric system

Set of well-defined passbands (or filters), with a known sensitivity to incident radiation

Photometry (astronomy)

Determination of light intensities of astronomical bodies

A star's outer shell from which light is radiated

Physical cosmology

Branch of astronomy

Second-brightest star in the constellation of Puppis

Constellation in the southern celestial hemisphere

Pinwheel Galaxy

Spiral galaxy in the constellation Ursa Major

Pisces (constellation)

Zodiac constellation straddling the celestial equator

Pisces–Cetus Supercluster Complex

A galaxy filament: largest known structures in universe: massive, thread-like formations

Piscis Austrinus

Constellation in the southern celestial hemisphere

Hypothetical Solar System planet

Innermost layer(s) of a planet

Planetary differentiation

Planetary habitability

Extent to which a planet is suitable for life as we know it

Measure of the mass of a planet-like object

Planetary nebula

Type of emission nebula

Planetary nebula luminosity function

Astronomical function

Planetary science

Science of planets and planetary systems

Planetary system

Set of non-stellar objects in orbit around a star

Solid objects thought to exist in protoplanetary disks and in debris disks

Planets beyond Neptune

Hypothetical planets further than Neptune

Star cluster in the constellation of Taurus

Natural phenomenon when the night lasts for more than 24 hours, occurring only inside the polar circles

Satellite orbit with high inclination

Polaris (disambiguation)

Topics referred to by the same term

Polarization in astronomy

Star in the constellation Gemini

Measurement relating to observed visual binary stars

Postal Alpha Numeric Encoding Technique

Type of barcode

Pre-main-sequence star

Star in the stage when it has not yet reached the main sequence

Pre-stellar core

An early phase in the formation of low-mass stars, before gravitational collapse produces a central protostar

Primordial fluctuations

Earliest theoretical cosmological structures

Japanese space probe launched in December 2014

Astronomical measure of the observed changes in the apparent places of stars in the sky

Dust ring surrounding large stars thousands of solar radii wide

Proton–proton chain

One of the fusion reactions by which stars convert hydrogen to helium

2nd phase of a formation of a planet

Protoplanetary disk

Rotating circumstellar disk of dense gas surrounding a young newly formed star

Protoplanetary nebula

Nebula surrounding a dying star

Short-lived satellite company

Proxima Centauri

Star in Centaurus constellation

Proxima Centauri b

Extrasolar planet in the constellation Centaurus

Pulsar in the constellation Vulpecula

Highly magnetized, rapidly rotating neutron star

Constellation in the southern celestial hemisphere

Constellation in the southern celestial hemisphere

Quadrans Muralis

Former constellation

Cold classical Kuiper belt object

The period in the evolution of the early universe

Compact exotic star which forms matter consisting mostly of quarks

Active galactic nucleus containing a supermassive black hole

Quintessence (physics)

Hypothetical fundamental force

Super star cluster in the constellation Dorado

Radial velocity

Velocity of an object as the rate of distance change between the object and a point

Radiative layer of stars

Radio astronomy

Subfield of astronomy that studies celestial objects at radio frequencies

Type of active galaxy that is very luminous at radio wavelengths

Radio spectrum pollution

Deviation of radio waves beyond allocations

Radio-quiet neutron star

Neutron star that does not emit radio waves

Rare Earth hypothesis

Hypothesis that complex extraterrestrial life is improbable and extremely rare

Swedish man-portable air-defense system

Recessional velocity

The rate at which an astronomical object becomes more distant from an observer

Recombination (cosmology)

Epoch at which charged electrons and protons first became bound to form electrically neutral hydrogen atoms

British comedy programme

Type of large cool stars that have exhausted their core hydrogen

Stars with a supergiant luminosity class with a spectral type of K or M

Red-giant branch

Stars powered by fusion of hydrogen in shell with an inactive core of helium

Eventual increase of wavelength in radiation during travel

Decrease in wavelength of electromagnetic radiation

Reflection nebula

Nebulosity in astronomy

Star in the constellation Leo

Cosmological process in the early universe

Constellation in the southern celestial hemisphere

Rho Ophiuchi cloud complex

Interstellar cloud

Star in the constellation Orion

Right ascension

Astronomical equivalent of longitude

A galaxy with a circle-like appearance

Planetary nebula in Lyra

Ring of cosmic dust orbiting an astronomical object

Rings of Jupiter

Rings of the planet Jupiter

Rings of Neptune

Rings of Saturn

Rings of Uranus

Planetary ring system of Uranus

Astronomical concept

Teardrop-shaped spacetime distortion near binary stars

A planetary-mass object that orbits the galaxy directly

Emission nebula in the constellation Monoceros

Nucleosynthesis pathway

RR Lyrae variable

Type of variable star

Constellation in the northern celestial hemisphere

Sagittarius (constellation)

Zodiac constellation in the southern celestial hemisphere

Radio source at the center of the Milky Way galaxy

A Supermassive black hole at the center of the Milky Way

A giant molecular cloud near the Milky Way's. center

Sagittarius Dwarf Spheroidal Galaxy

Saros (astronomy)

Series of eclipses separated by a saros period

Satellite galaxies of the Milky Way

Galaxies bound to the Milky Way

Satellite galaxy

Galaxy that orbits a larger galaxy due to gravitational attraction

Satellite system (astronomy)

Set of gravitationally bound objects in orbit

Sixth planet from the Sun

Saturn's hexagon

Hexagonal cloud pattern around north pole of Saturn

Scale factor (cosmology)

Parameter which characterizes the expansion of the universe

Collection of bodies in the extreme Solar System

Schwarzschild radius

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

Zodiac constellation in the southern celestial hemisphere

Sculptor (constellation)

Constellation in the southern celestial hemisphere

Sculptor Galaxy

Intermediate spiral galaxy in the constellation Sculptor

Scutum (constellation)

Constellation in the southern celestial hemisphere

Scutum–Centaurus Arm

Spiral arm of the Milky Way Galaxy

Search for extraterrestrial intelligence

Effort to find civilizations not from Earth

Sedna (dwarf planet)

Distant, small body in the Solar System

Study of the surface and shape of the Moon

September equinox

When sun appears directly over equator

Constellation, straddling the celestial equator, consisting of two non-connected parts (Serpens Caput and Serpens Cauda)

Constellation on the celestial equator

A class of active galaxies with very bright nuclei

Shape of the universe

The local and global geometry of the universe

Shapley Supercluster

Largest concentration of galaxies in our local universe

Timekeeping system

Astronomical database

Sirius Satellite Radio

Satellite radio service owned by Sirius XM

Visual perception of the sky and how it scatters and diffuses light.

Sloan Digital Sky Survey

Multi-spectral imaging and spectroscopic redshift survey

Small Magellanic Cloud

Dwarf irregular galaxy, satellite galaxy of the Milky Way

Supernova which formed the Crab Nebula, first observed in 1054

Supernova in the constellation Cassiopeia

Supernova in the NGC 5253 galaxy, first observed in 1972.

1987 supernova event in the constellation Dorado

Central region of the Sun

Periodic change in the Sun's activity

Natural phenomenon wherein the Sun is obscured by the Moon

A sudden flash of increased brightness on the Sun

Neutrinos produced in the core of the sun through various nuclear fusion reactions

The planets and their moons that orbit around the Sun

Stream of charged particles released from stars

Semi-annual astronomical event where the Sun is farthest from above the Earth's equator

Sombrero Galaxy

Spiral galaxy in the constellation Virgo

South Pole Wall

Massive cosmic structure

Study of plasmas that occur naturally in the universe

Space rendezvous

A series of orbital maneuvers to bring two spacecraft into the vicinity of each other

Spectral energy distribution

Topic in astronomy

Measure of the dependence of radiative flux density on frequency (astronomical term)

Spherical astronomy

Branch of astronomy about the celestial sphere

Italian manufacturer of fuel injection systems

Galaxy having a number of arms of younger stars

Nucleosynthesis pathway

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

Process by which dense regions of molecular clouds in interstellar space collapse to form stars

Small number of stars that orbit each other

Starburst galaxy

A galaxy undergoing an exceptionally high rate of star formation

Starburst region

Region of faster than normal star formation

Steady-state model

Model of the evolution of the universe

Stellar association

Astronomical object type

Stellar atmosphere

Outer region of the volume of a star

Stellar black hole

Black hole formed by a collapsed star

Stellar classification

Classification of stars based on spectral properties

The extremely hot, dense region at the center of a star

Aura of plasma that surrounds the Sun and other stars

Stellar evolution

Changes to stars over their lifespans

Stellar kinematics

Study of the movement of stars

Stellar magnetic field

Magnetic field generated by the convective motion of conductive plasma inside a star

Mass of a star in astronomy

Stellar nucleosynthesis

Process by which the natural abundances of the chemical elements within stars change due to nuclear fusion reactions

Stellar parallax

Apparent shift of position of a nearby star against the background of distant objects during Earth's orbital period

Stellar rotation

Angular motion of a star about its axis

Stellar structure

Structure of stars

Flow of gas ejected from the upper atmosphere of a star

Stephenson 2 DFK 1

Red supergiant star in the open cluster Stephenson 2

Steroidogenic acute regulatory protein

InterPro Family

Strong gravitational lensing

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

Structure formation

Formation of galaxies, galaxy clusters and larger structures from small early density fluctuations

A cool giant with approximately equal quantities of carbon and oxygen in its atmosphere

Sub-brown dwarf

Astronomical object of planetary mass that formed in the manner of stars

Star of luminosity class VI under the Yerkes spectral classification system

Type of star larger than main-sequence but smaller than a giant

Submillimetre astronomy

Astronomy with terahertz (< 1 mm)-range light

Substellar object

Astronomical object with insufficient mass to sustain nuclear fusion

Summer solstice

An astronomical phenomenon in which the Earth's axial tilt toward the Sun is at its maximum (currently 23.44°)

Summer Triangle

Star at the centre of the Solar System

Sungrazing comet

Comet that is extremely close to the sun during part of its orbit

Sunrise (disambiguation)

Topics referred to by the same term

Daily falling of the Sun below the horizon

Temporary phenomena on the Sun's photosphere

Sun-synchronous orbit

Type of geocentric orbit

Super star cluster

Astronomical object type

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

Large group of smaller galaxy clusters or galaxy groups

Superluminous supernova

A supernova at least ten times more luminous than a standard supernova

Supermassive black hole

Largest type of black hole

Full or new moon which appears larger due to coinciding with perigee

Star exploding at the end of its stellar evolution

Supernova nucleosynthesis

Production of the elements in a supernova explosion

Surface brightness

Measure of brightness of an astronomical object

Class of young variable star

Tarantula Nebula

H II region in the constellation Dorado

Single star in the constellation Cetus

Taurus (constellation)

Zodiac constellation straddling the celestial equator

Constellation in the southern celestial hemisphere

Terminator (solar)

Moving line that separates the illuminated day side and the dark night side of a planetary body

Terrestrial planet

Planet that is composed primarily of silicate rocks or metals.

Hypothetical planet that impacted Earth and created the Moon

Theoretical astronomy

Use of the analytical models of physics and chemistry to describe astronomical objects and astronomical phenomena

Structural component of some galaxies

Structural component of galaxies

Tidal acceleration

Cause of tidal locking

Situation in which an astronomical object's orbital period matches its rotational period

Time-domain astronomy

Study of how astronomical objects change with time

Timeline of the universe

A timeline of universe events since the Big Bang 13.8 billion years ago

Tip of the red-giant branch

Primary distance indicator used in astronomy

Largest moon of Saturn

The largest moon of Uranus

Transit of Mercury

A transit of Mercury across the Sun

Transit of Venus

Astronomical transit of Venus across the Sun

Trans-Neptunian object

Any object in the Solar System that orbits the Sun at a greater average distance than Neptune

Trapezium Cluster

Open cluster in the Orion Nebula in the constellation Orion

Ultra-cool red dwarf star in the constellation Aquarius

Constellation in the northern celestial hemisphere

Triangulum Australe

Constellation in the southern celestial hemisphere

Triangulum Galaxy

Spiral galaxy in the constellation Triangulum

Emission nebula in the constellation Sagittarius

Triple-alpha process

Nuclear fusion reaction chain converting helium to carbon

Largest moon of Neptune

Trojan (celestial body)

Smaller celestial body that shares a stable orbit with a much larger one

Period of time for the ecliptic longitude of the Sun to increase 360°

Constellation in the southern celestial hemisphere

Tully–Fisher relation

Trend in astronomy

Star in the constellation Hydra

Illumination of atmosphere when the Sun is not directly visible because it is below horizon

Variation in brightness and the position of stars due to atmospheric refraction

Type Ia supernova

Type of supernova in binary systems

Type Ib and Ic supernovae

Types of supernovae caused by a star collapsing

Type II Cepheid

Type II supernova

Explosion of a star 8 to 45 times the mass of the Sun

Galaxy morphology classification

UBV photometric system

Wide-band photometric system used in astronomy

Ultimate fate of the universe

Range of cosmological hypotheses and scenarios describing the eventual fate of the universe as we know it

Ultra-high-energy cosmic ray

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

Ultraviolet astronomy

Observation of electromagnetic radiation at ultraviolet wavelengths

Umbra, penumbra and antumbra

Distinct parts of a shadow

Unbarred spiral galaxy

Type of spiral galaxy without a central bar

Universe (gamer)

American professional Dota 2 player

Uppsala General Catalogue

Catalogue of galaxies visible from the northern hemisphere

Constellation in the northern sky

Constellation in the northern celestial hemisphere

Star in the constellation Scutum

Vampire literature

Speculative literary genre

Book by Robert Heinlein and Spider Robinson

Vega (disambiguation)

Topics referred to by the same term

Vela (constellation)

Constellation in the southern celestial hemisphere

Velocity dispersion

In astronomy, the statistical dispersion of velocities about the mean velocity for a cluster of stars or galaxies

Virgo (constellation)

Zodiac constellation straddling the celestial equator

Galaxy cluster in the constellation Virgo

Virgo Supercluster

Galactic supercluster containing the Virgo Cluster

Virgocentric flow

Preferred movement of Local Group galaxies towards the Virgo cluster caused by its overwhelming gravity, which separates bound objects from the Hubble flow of cosmic expansion

Visible-light astronomy

Encompasses a wide variety of astronomical observation via telescopes

Astronomy objects catalog

Void (astronomy)

Vast empty spaces between filaments with few or no galaxies

Constellation in the southern celestial hemisphere

Constellation in the northern celestial hemisphere

VY Canis Majoris

Star in the constellation Canis Major

Warm–hot intergalactic medium

Plasma that cosmologists believe exists between galaxies

Weak gravitational lensing

Gravitational deflection of light without creating noticeable extra images

Star-forming region in the constellation Serpens

Whirlpool Galaxy

Galaxy in the constellation Canes Venatici

White dwarf (disambiguation)

Topics referred to by the same term

Winter solstice

Astronomical phenomenon when the Earth's northern hemisphere's axial tilt toward the Sun is at minimum (currently -23.44°)

WISE 0855−0714

Sub-brown dwarf located near Earth

Wolf–Rayet star

Stars with unusual spectra showing prominent broad emission lines of highly ionised helium and nitrogen or carbon

Hypothetical topological feature of spacetime

X-ray astronomy

Branch of astronomy that uses X-ray observation

Class of binary stars

Class of astronomical objects that are X-ray sources

Yellow supergiant

Supergiant with a temperature similar to the sun

Young stellar object

Star in its early stage of evolution

Imaginary point directly above a particular location, on the imaginary celestial sphere

Star in the constellation Ophiuchus

Area of the sky divided into twelve signs

Faint solar glow caused by interplanetary dust at sunset and sunrise

Zone of Avoidance

Area in the sky obscured by the Milky Way.