This list brings together 20 astronomy words, running alphabetically from “Nebula” to “Nanoflare”. They cover everything from planets and stars to the tiny bursts of energy that heat the Sun’s outer layers. You’ll find them useful for stargazing, following space news, or simply understanding what scientists mean when they talk about the universe.
Astronomy words are the terms people use to describe objects, events, and phenomena found in space. Many trace back centuries, like “nadir”, a term navigators once relied on for finding their bearings by the stars. Others describe discoveries made only in recent decades, showing how the field keeps growing alongside our tools for exploring the sky.
Below you’ll find the table with Word, Definition, and Description.
Word: the astronomy term itself, listed alphabetically so you can quickly scan through the full set of 20 entries.
Definition: a short, plain-language explanation that tells you exactly what the term means without extra detail.
Description: a longer explanation that gives you context, examples, and interesting details to help the term make sense.
Astronomy words
| Word | Definition |
|---|---|
| Nebula | A cloud of gas and dust in space |
| Neptune | The eighth and outermost planet in the solar system |
| Neutron Star | The collapsed core of a massive star left after a supernova |
| Nova | A sudden, temporary brightening of a star |
| Nadir | The point on the celestial sphere directly below an observer |
| Node | A point where an orbit crosses a reference plane |
| Nucleosynthesis | The process that creates new atomic nuclei inside stars |
| Nutation | A small, periodic wobble in a rotating body’s axis |
| New Moon | The lunar phase when the Moon is invisible from Earth |
| Near-Earth Object | An asteroid or comet whose orbit brings it close to Earth |
| Northern Lights | A natural light display in polar skies, also called aurora borealis |
| Naked Singularity | A theoretical gravitational singularity not hidden by an event horizon |
| Neutrino | A nearly massless subatomic particle produced in nuclear reactions |
| Nemesis | A hypothetical, never-confirmed companion star to the Sun |
| Nautical Twilight | The twilight period when the horizon is still faintly visible |
| New General Catalogue | A historic catalogue of star clusters, nebulae, and galaxies |
| Newtonian Telescope | A reflecting telescope design using a curved primary mirror |
| Nucleus of a Comet | The solid, icy core at the center of a comet |
| Numerical Aperture | A measure of a telescope or lens’s light-gathering ability |
| Nanoflare | A tiny, brief burst of energy on the Sun’s surface |
Descriptions
Nebula
Nebulae are vast clouds of gas and dust scattered through galaxies, often glowing with the light of young stars. Many are stellar nurseries where new stars are born, while others are remnants left behind after a star dies.
Neptune
Neptune is a distant ice giant known for its deep blue color and ferocious winds, the fastest recorded in the solar system. It takes about 165 Earth years to complete one orbit around the Sun.
Neutron Star
A neutron star is an incredibly dense stellar remnant, packing more mass than the Sun into a sphere the size of a city. A teaspoon of its material would weigh billions of tons.
Nova
A nova occurs when a white dwarf pulls hydrogen from a companion star until it ignites in a burst of fusion, causing the system to flare dramatically brighter for a while before fading back down.
Nadir
The nadir is the imaginary point in the sky exactly opposite the zenith, straight down beneath an observer’s feet. It serves as a handy reference point when describing positions in the sky.
Node
Nodes are the two points where an orbiting body’s path crosses the plane of the ecliptic, one heading north and one heading south. Eclipses can only happen when the Sun and Moon are near these points.
Nucleosynthesis
Nucleosynthesis is how stars forge heavier elements from lighter ones through nuclear fusion, building everything from helium to iron in their cores. Nearly every element on Earth traces back to this stellar alchemy.
Nutation
Nutation is the subtle nodding motion layered on top of Earth’s slower axial precession, caused mainly by the Moon’s shifting gravitational pull. It makes Earth’s axis trace a slightly wavy path over time.
New Moon
A new moon happens when the Moon sits between Earth and the Sun, its lit side facing away from us. It marks the start of the lunar cycle and offers the darkest, best nights for stargazing.
Near-Earth Object
Near-Earth objects are small bodies, mostly asteroids, whose orbits bring them within roughly 30 million miles of Earth’s path around the Sun. Astronomers track them closely to rule out any future collision risk.
Northern Lights
The Northern Lights are shimmering curtains of green, pink, and purple light caused by charged particles from the Sun colliding with Earth’s atmosphere near the magnetic poles. They’re best seen on clear nights at high latitudes.
Naked Singularity
A naked singularity is a hypothetical point of infinite density that, unlike the ones inside black holes, wouldn’t be shielded behind an event horizon. Most physicists doubt these can actually exist in nature.
Neutrino
Neutrinos are ghostly particles created in the Sun’s core and in supernovae, streaming through space and matter with almost no interaction at all. Trillions pass harmlessly through your body every single second.
Nemesis
Nemesis was a proposed dim star some scientists suggested orbits the Sun far beyond Pluto, periodically disturbing comets in the outer solar system. Despite extensive searches, no evidence of it has ever been found.
Nautical Twilight
Nautical twilight occurs when the Sun sits between 6 and 12 degrees below the horizon, dim enough to reveal bright stars yet light enough to still make out the horizon line, historically prized by sailors navigating by the stars.
New General Catalogue
The New General Catalogue, or NGC, is a 19th-century listing of nearly 8,000 deep-sky objects compiled by astronomer John Dreyer. Amateur astronomers still use its NGC numbers to identify galaxies and nebulae today.
Newtonian Telescope
Invented by Isaac Newton, this telescope uses a curved mirror to gather light and a small flat mirror to redirect it to an eyepiece on the side of the tube. It remains a popular, affordable design among amateur astronomers.
Nucleus of a Comet
A comet’s nucleus is its small, solid body of ice, dust, and rock, often just a few miles across. As it nears the Sun, the nucleus heats up and releases gas and dust that form the comet’s glowing coma and tail.
Numerical Aperture
Numerical aperture describes how well an optical instrument can gather light and resolve fine detail, based on the angle of light it can accept. Higher values generally mean sharper, brighter images through the eyepiece.
Nanoflare
Nanoflares are miniature explosive events too small to see individually, thought to occur constantly across the Sun’s outer layers. Scientists suspect their combined heat may help explain why the Sun’s corona is far hotter than its surface.