This list covers 24 astronomy words, running from “Waning Crescent” to “W Virginis Star”. They cover everything from moon phases and star types to techniques scientists use to hunt for planets and dark matter. Skywatchers, students, and curious readers use terms like these to describe what they see at night and to follow how astronomers study the universe.
Astronomy words are the specific terms scientists and stargazers use to name objects, events, and phenomena beyond Earth. Many started as everyday descriptions, like the “wobble” a star makes when tugged by an orbiting planet, before becoming standard scientific vocabulary. Others, such as “white dwarf” or “wormhole”, have crossed over into popular culture through books and films.
Below you’ll find the table with the word, its definition, and a fuller description.
Word: the specific astronomy term, shown exactly as it’s commonly used by astronomers and in science writing.
Definition: a short, plain-language explanation that tells you what the word means in a single glance.
Description: extra context that helps you understand where you’d encounter the term and why it matters.
Astronomy words
| Word | Definition |
|---|---|
| Waning Crescent | A moon phase between third quarter and new moon |
| Waning Gibbous | A moon phase between full moon and third quarter |
| Waxing Crescent | A moon phase between new moon and first quarter |
| Waxing Gibbous | A moon phase between first quarter and full moon |
| Water Hole | The quiet radio frequency band between 1,420 and 1,720 MHz |
| Water World | A hypothetical exoplanet mostly or entirely covered by ocean |
| Weak Lensing | The subtle bending of light by large-scale mass distributions |
| Weightlessness | The sensation of having no perceptible weight |
| Whirlpool Galaxy | A classic spiral galaxy also known as M51 |
| White Dwarf | The dense, burnt-out core left behind by a sun-like star |
| White Hole | A hypothetical object that is the theoretical reverse of a black hole |
| Wide Binary | A pair of stars orbiting each other at a great distance |
| Widmanstätten Pattern | A crystal pattern found in some iron meteorites |
| Wien’s Law | A formula linking a hot object’s temperature to its peak light color |
| WIMP | Weakly Interacting Massive Particle, a candidate for dark matter |
| Winter Solstice | The point when a hemisphere has its shortest day of the year |
| Winter Triangle | A large seasonal star pattern visible in winter skies |
| Wobble Method | A technique for detecting planets by a star’s tiny back-and-forth motion |
| Wolf Number | A standard index of sunspot activity |
| Wolf-Rayet Star | A rare, extremely hot and massive star shedding its outer layers |
| Wolf-Lundmark-Melotte Galaxy | A small, isolated dwarf galaxy in the Local Group |
| Wormhole | A theoretical tunnel-like shortcut through spacetime |
| W Ursae Majoris Variable | A type of eclipsing binary star sharing a common envelope |
| W Virginis Star | A type of pulsating variable star found in older stellar populations |
Descriptions
Waning Crescent
A thin sliver of the Moon visible before dawn, shrinking each night as it heads toward the dark, invisible new moon phase.
Waning Gibbous
The stage right after full moon when the illuminated portion is still large but steadily shrinking night by night.
Waxing Crescent
The earliest visible sliver of the Moon after new moon, growing a little larger and brighter each evening.
Waxing Gibbous
A moon phase where more than half the disc is lit and growing, just before the Moon turns fully full.
Water Hole
A relatively noise-free slice of radio spectrum, bounded by hydrogen and hydroxyl emission lines, long favored for SETI listening campaigns.
Water World
A class of exoplanet thought to have little or no exposed land, with deep global oceans possibly hundreds of kilometers thick.
Weak Lensing
A gentle distortion of background galaxy shapes caused by foreground mass, used by astronomers to map dark matter across the universe.
Weightlessness
The floating condition experienced by astronauts in orbit, caused by continuous free-fall around Earth rather than an absence of gravity.
Whirlpool Galaxy
A photogenic, face-on spiral galaxy in Canes Venatici, notable for its well-defined arms and a smaller companion galaxy merging with it.
White Dwarf
A small, extremely dense stellar remnant that has exhausted its fuel and slowly cools over billions of years after a star’s death.
White Hole
A speculative object from which matter and light could only escape, never enter, predicted by some solutions to general relativity but never observed.
Wide Binary
Two gravitationally bound stars separated by hundreds or thousands of times the Earth-Sun distance, orbiting one another very slowly.
Widmanstätten Pattern
An interlocking, striped crystalline structure revealed when certain iron meteorites are cut and etched, formed by extremely slow cooling in a parent asteroid.
Wien’s Law
A physics rule stating that hotter stars emit their brightest light at shorter wavelengths, letting astronomers estimate a star’s temperature from its color.
WIMP
A hypothetical heavy particle that barely interacts with ordinary matter, long considered a leading explanation for the universe’s unseen dark matter.
Winter Solstice
The astronomical event marking the Sun’s lowest path across the sky, occurring around December or June depending on hemisphere.
Winter Triangle
An asterism formed by the bright stars Sirius, Procyon, and Betelgeuse, easily spotted dominating the evening sky during winter months.
Wobble Method
Also called the radial velocity method, it detects unseen exoplanets by measuring the slight gravitational tug that makes their host star wobble.
Wolf Number
A numerical count of visible sunspots and sunspot groups, used since the 1800s to track the Sun’s roughly eleven-year activity cycle.
Wolf-Rayet Star
A short-lived, luminous star blasting off its outer envelope in powerful stellar winds, often a precursor to a supernova explosion.
Wolf-Lundmark-Melotte Galaxy
A faint, irregular dwarf galaxy sitting at the remote edge of our Local Group, notable for being one of its most isolated members.
Wormhole
A speculative structure predicted by general relativity that could, in theory, connect two distant points in space and time through a shortcut.
W Ursae Majoris Variable
A close binary star system where both stars touch and share material, producing smooth, continuous brightness changes as they eclipse one another.
W Virginis Star
A yellow, pulsating star similar to a Cepheid but older and fainter, used by astronomers as a distance marker in ancient star clusters.