The Origins Of 10 Space Terms That Are Out Of This World

Words like “nebula,” “galaxy” and “cosmos” can summon up lots of romantic images of space exploration, but where did these terms come from in the first place?
astronaut floating in space by a satellite depicting space words

In the 21st century, we know a decent amount about astronomy. There’s plenty of phenomena still shrouded in mystery — that’s what keeps it exciting! — but we’ve explored a decent amount of our own cosmic stomping ground. The words we use to describe space, however, come from long ago — from way before we had this understanding. Despite being an incredibly scientific field, astronomy is filled with words that allude to Roman mythology, archaic terms and ancient misconceptions. We explored 10 of our favorite space words to find out how our ancestors named the sky.

Common Space Words And Their Nebulous Origins


Asteroids can easily be confused with a comet or a meteor (see below), but they are larger than both and they’re also locked in a stable orbit around a star. The asteroid belt, for example, is the huge number of rocks that orbit our Sun. The word can be sourced all the way back to the Proto-Indo-European *ster-, meaning “star,” combined with *-eidos, which means “form” or “shape.” Asteroids aren’t actually star-like, based on our current understanding, but the word is still used.


Comets are balls of ice and rock left over from the formation of planets billions of years ago. They often have long tails that trail behind them, which is caused by their ice melting as they pass by stars (this is not the same as shooting stars, which we will discuss later). Comets have been observed for thousands of years, but their name comes from the Greek word komē, which means “long hair.” The Greeks called these rocks komētēs because their tails looked like long strands of hair in the sky.


Constellations are the shapes that humans have discerned out of the stars that dot the sky. Various societies have created their own constellations, but the ancient Greeks named most of the constellations we know today (though they may have ripped them off from earlier civilizations). The word “constellation” itself, however, comes from Latin. It combines the prefix com, meaning “together,” with stellare, the past participle of “to shine,” which itself derives from stella (“star”).

Space Word Origins: view of Earth from the space shuttle


Cosmos refers to the whole universe and everything we know in it. Unlike many of the space words on this list, “cosmos” hasn’t been around for that long, at least in the sense in which we use it today. It comes from the Greek kosmos, meaning “order” or “world,” but it didn’t become popularized as a way to describe the universe until the publication of naturalist Alexander von Humboldt’s Cosmos (or Kosmos in the original Greek). The book was based on a lecture series in which Humboldt attempted to describe the order of the universe. It has since become strongly associated with wonder and mystery thanks to Carl Sagan’s documentary series Cosmos, originally aired in 1980, and revived by Neil deGrasse Tyson in 2014.


The seven other planets in our solar system (and the one dwarf planet; sorry Pluto) are all named after Roman gods. Earth, however, is not. In fact, every language has a different word for Earth, and what unites them all is that the word originally referred not to a whole planet, but to the literal ground beneath our feet. English’s word comes from the Proto-Germanic ertho, which was indeed a word for “dirt” or “soil.”

The Milky Way Galaxy

The Milky Way” is a weird term, even by space words standards. It might be even more shocking to learn that galaxy comes from the Greek phrase galaxias kyklos, which literally means “milky circle.” Milky Way, on the other hand, was translated from the Latin via lactea. Both of these terms come from a time in history when scientists assumed that there was only one galaxy. And when they beheld it, well, it looked kind of milky. When other massive space structures were discovered, the word “galaxy” then had to be applied to other parts of the universe.

The naming of other galaxies has been eclectic. One of our closest neighbors, the Andromeda Galaxy, gets its name from a figure in Greek mythology. There are also galaxies named for their appearance, like the Whirlpool Galaxy, the Pinwheel Galaxy and the Sombrero Galaxy. There are also a few named after their discoverers, including Bode’s Galaxy and Hoag’s Object.


Like asteroids, meteoroids are in orbit around the Sun (or any other star), but they’re smaller. You might know them better as “shooting stars.” When a meteoroid enters the Earth’s atmosphere, it becomes a meteor. And if the meteor doesn’t entirely burn up on its passage down to Earth, it becomes a meteorite. The word “meteor” comes from the Greek ta meteōra, which was used to refer to any celestial phenomenon at all. It was formed by using meta (“by means of”) and -aoros (“lifted, suspended”). It wasn’t until the late 16th century that the term was specifically used to describe what are now called meteors.

Space Name Origins: A shooting star over a mountain range


The Earth has the capital “M” Moon, and other planets have their own moons with various names (usually from Roman mythology). The word “moon” can be traced back a long way, all the way to Proto-Indo-European me(n)ses-. This word is also the root of “month,” and is itself derived from the Proto-Indo-European me-, which meant “to measure.” The Moon, way back in the day, was the main method of measuring time because of its phases, so it makes sense the Moon and the months are forever entwined. The word was applied to other moons when they first started being discovered in the 17th century.

As a brief aside, the first attestation of “moon” as a verb to refer to someone exposing their buttocks dates back to 1968, when it popped up in American slang. Comparing butts to moons, however, has been done since the mid-18th century.


A nebula is a cloud of dust or gas that exists in space, and they’re the basis of the beautiful space photography that’s filled with colors and textures. The word nebula comes from the Latin nebula, which means “mist, vapor, fog” (and it can be traced back even further to a Proto-Indo-European root). The word wasn’t applied to space clouds until the 1730s, however, so the choice of the Latin term was somewhat arbitrary (though Latin is a common choice in many scientific fields).


Here comes the Sun to round out our list. Unfortunately, “sun” doesn’t have a very exciting etymology, mainly because the Sun didn’t exactly need to be discovered. It’s just always been up there, shining over us. Thus, the word also goes all the way back to Proto-Indo-European — the oldest ancestor of English we know of — where the great fire in the sky was called *s(u)wen-.

*Please note: we don’t actually have a written or spoken record of Proto-Indo-European, so all words with an asterisk next to them are a reconstructed guess of what the word would be. The parentheses and hyphen also allude to this.

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