This list covers 72 astronomy words, running from “Callisto” to “Cygnus.” You’ll find moons, constellations, spacecraft, and cosmic phenomena side by side, each explained in plain language. Skywatchers, students, and curious readers use lists like this to build a working vocabulary for reading star charts, following space news, or simply naming what they see overhead.
Astronomy words are the terms scientists and stargazers use to describe objects, events, and processes beyond Earth’s atmosphere. Some names trace back to ancient mythology, like Cassiopeia’s vain queen or Corona Borealis, Ariadne’s jeweled crown, while others describe cutting-edge tools like the Chandra X-ray Observatory. Together, they give us a shared language for talking about the universe.
Below you’ll find the table with Word, Definition, and Description.
Word: the astronomy term itself, listed alphabetically so you can scan the page or jump straight to the one you’re looking for.
Definition: a short, plain-language explanation that tells you what the word means at a glance, without any jargon.
Description: extra context and background that helps you understand why the term matters and how it fits into the bigger picture of astronomy.
Astronomy words
| Word | Definition |
|---|---|
| Callisto | The second-largest moon of Jupiter |
| Camelopardalis | A faint northern constellation representing a giraffe |
| Cancer | A faint zodiac constellation representing a crab |
| Canes Venatici | A small northern constellation representing hunting dogs |
| Canis Major | A southern constellation representing the “Greater Dog” |
| Canis Minor | A small constellation representing the “Lesser Dog” |
| Capricornus | A faint zodiac constellation representing a sea-goat |
| Carina | A southern constellation representing a ship’s keel |
| Cassini Division | A gap in Saturn’s ring system |
| Cassini-Huygens | A NASA-ESA mission that explored Saturn and its moons |
| Cassiopeia | A distinctive W-shaped northern constellation |
| Cataclysmic Variable | A binary star system with a white dwarf pulling material from a companion |
| CCD (Charge-Coupled Device) | A light-sensitive electronic chip used to capture astronomical images |
| Celestial Equator | The projection of Earth’s equator onto the sky |
| Celestial Mechanics | The branch of astronomy studying the motions of celestial bodies |
| Celestial Navigation | The practice of determining position using the sun, moon, and stars |
| Celestial Pole | The point in the sky directly above Earth’s rotational axis |
| Celestial Sphere | An imaginary sphere surrounding Earth used to map the positions of stars |
| Centaur | A class of small icy solar system bodies orbiting between Jupiter and Neptune |
| Centaurus | A large southern constellation representing a centaur |
| Cepheid Variable | A pulsating star whose brightness changes in a predictable cycle |
| Cepheus | A northern constellation representing a mythological king |
| Cetus | A large constellation representing a sea monster or whale |
| Chandra X-ray Observatory | A NASA space telescope that detects X-rays from cosmic sources |
| Chamaeleon | A small, faint southern constellation representing a chameleon |
| Charon | The largest moon of the dwarf planet Pluto |
| Chromatic Aberration | A lens defect that causes colored fringing around images |
| Chromosphere | A reddish layer of the sun’s atmosphere above its visible surface |
| Chondrite | A stony meteorite containing small mineral grains called chondrules |
| Chondrule | A small, round mineral grain found in some meteorites |
| Circinus | A small, faint southern constellation representing a drafting compass |
| Circumpolar Star | A star that never sets below the horizon from a given location |
| Circumstellar Disk | A disk of gas and dust orbiting a young star |
| Close Binary | A pair of stars orbiting each other at a small separation |
| Coma | The fuzzy cloud of gas and dust surrounding a comet’s nucleus |
| Coma Berenices | A faint northern constellation representing Queen Berenice’s hair |
| Comet | A small icy body that develops a glowing coma and tail near the sun |
| Command Module | The crew-carrying capsule of a spacecraft, as used in the Apollo program |
| Conjunction | An event when two celestial objects appear close together in the sky |
| Constellation | A recognized pattern or grouping of stars in the sky |
| Continuum | A smooth, unbroken spectrum of light without distinct emission or absorption lines |
| Contact Binary | A pair of stars so close their surfaces are touching |
| Convective Zone | The outer layer of a star where energy moves via convection |
| Copernican Principle | The idea that Earth holds no special or privileged position in the universe |
| Core (Stellar) | The dense central region of a star where nuclear fusion occurs |
| Corona | The outermost, super-heated layer of the sun’s atmosphere |
| Corona Australis | A small southern constellation representing a wreath or crown |
| Corona Borealis | A small northern constellation representing a crown |
| Coronal Hole | A region of the sun’s corona that is cooler and less dense |
| Coronal Mass Ejection | A massive burst of plasma and magnetic field expelled from the sun |
| Corvus | A small constellation representing a crow or raven |
| Cosmic Dust | Tiny solid particles scattered throughout space |
| Cosmic Inflation | A theorized period of extremely rapid expansion just after the Big Bang |
| Cosmic Microwave Background | The faint afterglow radiation left over from the Big Bang |
| Cosmic Ray | A high-energy particle traveling through space at near light speed |
| Cosmic String | A hypothetical, extremely thin defect in the fabric of spacetime |
| Cosmic Web | The large-scale filamentary structure connecting galaxies across the universe |
| Cosmic Year | The time it takes the sun to orbit once around the center of the Milky Way |
| Cosmodrome | A launch and testing facility for spacecraft, especially in Russia |
| Cosmogony | The scientific study of the origin of the universe |
| Cosmological Constant | A term in Einstein’s equations representing the energy density of empty space |
| Cosmology | The scientific study of the origin, structure, and fate of the universe |
| Cosmonaut | A Russian or Soviet-trained astronaut |
| Cosmos | Another word for the universe as an orderly, structured whole |
| Coudé Telescope | A telescope design that directs light to a fixed, separate observation room |
| Crater | A bowl-shaped depression formed by a meteorite or asteroid impact |
| Crater (constellation) | A small constellation representing a cup or chalice |
| Crux | A small southern constellation known as the Southern Cross |
| CubeSat | A small, standardized satellite built from cube-shaped modules |
| Culmination | The moment a celestial object reaches its highest point in the sky |
| Curiosity Rover | A NASA rover exploring Mars since 2012 |
| Cygnus | A prominent northern constellation representing a swan |
Descriptions
Callisto
A heavily cratered ice-and-rock moon of Jupiter, Callisto has one of the oldest, most battered surfaces in the solar system, hinting at billions of years with little geological activity.
Camelopardalis
This large but dim constellation sits near the north celestial pole and has few bright stars, making it a challenge for stargazers to trace with the naked eye.
Cancer
Best known for the star cluster Praesepe (the Beehive Cluster), Cancer is one of the dimmer zodiac constellations, tucked between Gemini and Leo.
Canes Venatici
Home to the Whirlpool Galaxy, this modest constellation near the Big Dipper’s handle is a favorite target for galaxy-hunting astronomers.
Canis Major
Canis Major contains Sirius, the brightest star in the night sky, and is traditionally pictured as one of the hunter Orion’s hunting dogs.
Canis Minor
This compact constellation is anchored by Procyon, one of the brightest stars visible from Earth, and forms part of the Winter Triangle.
Capricornus
One of the oldest recognized constellations, Capricornus is depicted as a hybrid goat-fish and is among the dimmest of the zodiac signs.
Carina
Once part of a larger “ship” constellation, Carina hosts Canopus, the second-brightest star in the sky, and the massive, unstable star Eta Carinae.
Cassini Division
This roughly 4,800-kilometer gap between Saturn’s A and B rings is carved out by the gravitational pull of the moon Mimas and is visible through amateur telescopes.
Cassini-Huygens
Launched in 1997, this spacecraft orbited Saturn for over a decade, dropping the Huygens probe onto Titan and revealing plumes erupting from the moon Enceladus.
Cassiopeia
Named for a vain queen in Greek mythology, Cassiopeia’s zigzag pattern of bright stars makes it one of the easiest constellations to spot year-round.
Cataclysmic Variable
These close star pairs can flare up dramatically and unpredictably in brightness as stolen gas crashes onto the white dwarf’s surface.
CCD (Charge-Coupled Device)
CCDs revolutionized astronomy by replacing photographic film, letting telescopes record faint, distant objects digitally with far greater sensitivity.
Celestial Equator
This imaginary line divides the sky into northern and southern halves and serves as a key reference for mapping the positions of stars and planets.
Celestial Mechanics
This field uses physics and mathematics to predict how planets, moons, and other objects move under gravity’s influence.
Celestial Navigation
Sailors and pilots have long used this technique, measuring the angles of celestial bodies to figure out their location on Earth.
Celestial Pole
Stars appear to circle around this fixed point, which is currently marked closely by Polaris in the northern sky.
Celestial Sphere
Astronomers use this model as if all stars were painted on the inside of a giant globe, simplifying how we describe their locations.
Centaur
These objects behave like a cross between asteroids and comets, often developing comet-like activity as their unstable orbits bring them closer to the sun.
Centaurus
Home to Alpha Centauri, the closest star system to our sun, Centaurus is one of the largest and richest constellations in the sky.
Cepheid Variable
Because their pulsation period reveals their true brightness, Cepheids act as reliable “standard candles” that astronomers use to measure distances across the universe.
Cepheus
Shaped like a simple house outline, Cepheus sits near the north celestial pole and lends its name to the Cepheid variable stars.
Cetus
Cetus contains the famous variable star Mira, whose brightness swings dramatically over about 11 months.
Chandra X-ray Observatory
Launched in 1999, Chandra studies extremely hot regions of the universe, like the aftermath of exploded stars and material swirling into black holes.
Chamaeleon
Introduced by 16th-century astronomers, this dim constellation lies near the south celestial pole and contains few notable naked-eye stars.
Charon
Charon is so large relative to Pluto that the two are sometimes considered a binary system, orbiting a point between them rather than Pluto alone.
Chromatic Aberration
This optical flaw occurs because different wavelengths of light bend by different amounts, a common headache for telescope and camera lens designers.
Chromosphere
Normally hidden by the sun’s glare, the chromosphere becomes visible as a thin pink ring during a total solar eclipse.
Chondrite
These primitive meteorites are considered leftover building blocks from the early solar system, largely unchanged for billions of years.
Chondrule
Formed from molten droplets in the early solar system, chondrules give clues about the conditions present before the planets formed.
Circinus
One of the least conspicuous constellations, Circinus lies near the bright star Alpha Centauri but is difficult to observe without dark skies.
Circumpolar Star
Depending on your latitude, certain stars circle continuously around the celestial pole, always staying visible throughout the night.
Circumstellar Disk
These disks are the raw material from which planets are thought to form, gradually clumping together over millions of years.
Close Binary
In these tightly bound systems, the stars can interact strongly, sometimes transferring material or even merging over time.
Coma
As a comet nears the sun, ice on its surface vaporizes, creating this glowing envelope that can grow larger than a planet.
Coma Berenices
This dim constellation is notable for containing a rich cluster of nearby galaxies visible in amateur telescopes.
Comet
As these frozen leftovers from the solar system’s formation approach the sun, heat causes them to release gas and dust, creating their signature tails.
Command Module
This was the only part of the Apollo spacecraft designed to return astronauts safely through Earth’s atmosphere after lunar missions.
Conjunction
Conjunctions often involve planets or the moon lining up from Earth’s viewpoint, offering striking naked-eye sky-watching opportunities.
Constellation
The International Astronomical Union recognizes 88 official constellations, which serve as a way to organize and name regions of the sky.
Continuum
Astronomers study the continuum of an object’s light to learn about its temperature and overall energy output.
Contact Binary
These stellar duos share an outer envelope of gas and can eventually merge into a single, more massive star.
Convective Zone
In the sun, hot plasma rises and cooler plasma sinks in this layer, much like boiling water, carrying energy toward the surface.
Copernican Principle
Named after Nicolaus Copernicus, this principle underlies much of modern cosmology, assuming our location in the cosmos is unremarkable.
Core (Stellar)
A star’s core is where immense pressure and temperature fuse hydrogen into helium, generating the energy that makes stars shine.
Corona
Visible as a pale halo during a total solar eclipse, the corona is mysteriously far hotter than the sun’s visible surface beneath it.
Corona Australis
This faint arc of stars lies near Sagittarius and represents the “southern crown” in ancient sky lore.
Corona Borealis
Shaped like a graceful semicircle of stars, this constellation depicts the jeweled crown of Ariadne from Greek mythology.
Coronal Hole
These dark patches allow fast-moving solar wind to escape more freely, sometimes triggering auroras on Earth.
Coronal Mass Ejection
These eruptions can hurtle billions of tons of solar material into space, occasionally disrupting satellites and power grids when aimed at Earth.
Corvus
This compact, boxy group of four stars sits near Virgo and is one of the more recognizable minor constellations.
Cosmic Dust
Made of rock, ice, or carbon compounds, cosmic dust plays a key role in star and planet formation and shapes how galaxies glow.
Cosmic Inflation
This brief but explosive growth spurt is thought to explain why the universe looks so uniform and flat on the largest scales.
Cosmic Microwave Background
This nearly uniform microwave glow fills the entire sky and offers a snapshot of the universe as it was about 380,000 years after its birth.
Cosmic Ray
Originating from sources like supernovae and black holes, these particles constantly bombard Earth’s atmosphere from all directions.
Cosmic String
These theoretical structures, if they exist, would stretch across the universe and carry enormous mass and gravitational influence.
Cosmic Web
Made of dark matter and gas, this vast network of threads and voids is where galaxies and galaxy clusters cluster and align.
Cosmic Year
One cosmic year lasts roughly 225 to 250 million Earth years, meaning the sun has completed only a couple dozen since it formed.
Cosmodrome
The Baikonur Cosmodrome in Kazakhstan is the most famous example, having launched the first satellite and first human into space.
Cosmogony
This field explores how the cosmos, and the structures within it, first came into being.
Cosmological Constant
Often linked to dark energy, this constant helps explain why the universe’s expansion is accelerating rather than slowing down.
Cosmology
Cosmologists piece together evidence from light, gravity, and particle physics to understand how the universe began and where it’s headed.
Cosmonaut
The term distinguishes space travelers trained through Russia’s space program from American “astronauts” or Chinese “taikonauts.”
Cosmos
The term emphasizes the universe’s harmony and order, in contrast to chaos, and is often used interchangeably with “universe.”
Coudé Telescope
This layout keeps heavy instruments stationary while the telescope itself moves, making it easier to attach large, precise scientific equipment.
Crater
Craters pockmark the surfaces of the moon, Mercury, and other bodies lacking atmospheres thick enough to burn up incoming debris.
Crater (constellation)
Perched on the back of the constellation Hydra, this faint grouping of stars is one of the more obscure entries in the night sky.
Crux
Crux is prominent on the flags of several southern-hemisphere nations and is used by navigators to locate the south celestial pole.
CubeSat
These miniature satellites have made space research more affordable, allowing universities and small teams to launch their own missions.
Culmination
At culmination, an object crosses the observer’s meridian, marking the peak of its nightly arc across the heavens.
Curiosity Rover
About the size of a small car, Curiosity has trundled across Gale Crater, drilling rocks and searching for signs that Mars once could have supported life.
Cygnus
Also known as the Northern Cross, Cygnus lies along the Milky Way and contains the bright star Deneb, one corner of the Summer Triangle.