Why Is The Milky Way Called ‘Milky Way’?

The Milky Way gets its name from the faint, milky-white band of light it forms across a dark night sky, the combined glow of countless stars in our galaxy’s disk. The ancient Romans called it via lactea ("the milky road"), and the word "galaxy" itself comes from the Greek galaxias, from gala, meaning milk.

The way some things are named is truly amazing. In one of our previous articles, we talked about the reason that the output power of machines is measured in ‘horsepower‘. Now, it’s time to talk about our own beloved galaxy, which, in addition to our solar system, houses hundreds of billions of stars (and at least as many planets), along with countless comets and other celestial bodies.

But why is it called the ‘Milky Way’? Well, before we get into the details of that, let’s rewind a little bit.

What Is The Milky Way?

If I was telling this to a 7-year-old, I’d say that the Milky Way is the galaxy in which we live. It’s a gigantic barred spiral galaxy whose stellar disk is around 100,000 light years across (more recent measurements suggest the outer disk may extend out to roughly 200,000 light years). And let me tell you, one light year equals 9.461 trillion kilometers (5.878625 trillion miles)! It’s so incredibly massive that using the word ‘big’ to describe it feels like an insult to its enormous size.

Given how mammoth the Milky Way is, it comes as no surprise that it is home to countless celestial bodies. It’s estimated to hold somewhere between 100 and 400 billion stars (200 billion is a common middle estimate) and at least 100 billion planets, plus billions of other objects flying through the Milky cosmos. These are still only estimates, since we don’t really know for sure the colossal extent of its contents.

Note that the Milky Way is not the only galaxy out there; it’s actually part of a large bunch of galaxies known as the Local Group. The Local Group now has more than 100 known member galaxies; ours is the second-largest, followed by the Triangulum Galaxy (also known as M33). The largest member of the group, the Andromeda Galaxy (also called M31), has long been thought to be on a collision course with our galaxy, though a 2024 reassessment using Gaia and Hubble data suggests the future merger is less certain than astronomers once believed. Our solar system is located within the disk of the Milky Way, but far from its center, on one of the spiral-shaped concentrations of dust and gas called the Orion Arm.

Now that you have a little background about our home galaxy, let’s find out why it has such an unusual name.

Why Is It Called The ‘Milky Way’?

Our galaxy owes its name to the way it looks. If you’ve ever observed a picture of the Milky Way, you will have noticed a dim glowing band racing across the night sky surrounded on all sides by countless indistinguishable bright stars.

The Ancient Romans called it ‘via lactea’ which quite literally meant a ‘milky way/road’. Also, the word ‘galaxy’ is derived from a Greek word for ‘milk’. Although there is not absolute proof as to why they named our galaxy as something related to milk, some researchers believe what seems to be the most likely and also most plausible reason for the name – its appearance against the night sky.

The milky band that you see on the edge of the Milky Way is actually a concentrated chunk of millions upon millions of stars that shine incredibly brightly. Also, the image of the Milky Way that we see up in the night sky in unpolluted areas (especially remote, rural locations) is on its side; it is due to the angle of viewing that the galaxy appears to be a thin, shiny arc of light, rather than an enormous, bright disk.

Who Named The Milky Way, And When?

So who actually came up with the name? The honest answer is that no single person did, and the label is far older than the science behind it. Our modern name is a direct translation of the Latin via lactea, the term the Romans used, and they in turn borrowed it from the ancient Greeks, who called the band galaxias kyklos (γαλαξίας κύκλος), meaning the ‘milky circle’. That same Greek root for milk, gala, is exactly where we get the word ‘galaxy’ today.

The Greeks even had a myth to explain that milky streak. In one popular version, Zeus wanted his infant son Heracles (the Roman Hercules), born to a mortal mother, to gain divine powers, so he set the baby to nurse at the breast of his sleeping wife Hera. When Hera woke and realized she was feeding a stranger’s child, she pushed him away, and the milk that sprayed across the heavens became the Milky Way. It’s a tidy story, though it’s really mythology stitched onto a name people already used, rather than the actual source of the word.

The science took a lot longer to catch up. The Greek thinkers Democritus and Anaxagoras guessed, remarkably, that the faint glow might be the combined light of countless distant stars, while Aristotle argued it was something burning high in Earth’s atmosphere. Nobody could settle the matter with the naked eye. That had to wait until 1610, when Galileo Galilei pointed his new telescope at the band and, as he reported in his book Sidereus Nuncius (‘The Starry Messenger’), watched the ‘milky’ smear resolve into thousands of individual stars, far too faint and crowded to separate by eye. The ancient name, it turned out, had been describing exactly what the thing is all along: the merged light of our galaxy’s stars.

Different Cultures, Different Names

Although the name Milky Way is the predominant nickname of our galaxy, it’s interesting to note that various cultures often use different names to refer to our spot in the cosmos. For example, Norwegians call it ‘Melkeveien‘, the Chinese have a name for it that literally means ‘silver river’, in Germany it’s called ‘Milchstrasse‘, and it’s called ‘Aakaash-ganga‘ – meaning ‘Ganges river of Heaven’ – in Hindi.

Travel a bit further and the imagery only gets richer. In Japanese the galaxy is Ama-no-gawa, the ‘River of Heaven’, while Korean keeps the East Asian theme with Eunhasu, another ‘silver river’. Several northern European peoples, including Finns and Estonians, called it the ‘Birds’ Path’, having noticed that migrating birds seemed to follow the band south each autumn. In Hungarian folklore it is Hadak Útja, the ‘Road of the Warriors’, down which a mythic horseman was said to ride to defend his people. Old Armenian tradition, more down-to-earth, named it the ‘Straw Thief’s Way’, after a legend of a thief scattering stolen straw across the sky.

Some of the most striking names come from the southern skies, where the Milky Way passes high overhead and looks far brighter than it does from northern cities. The Aboriginal Gomeroi people of Australia famously read the dark dust lanes within the band as a giant ‘Emu in the Sky’ (Dhinawan), a constellation made of shadow rather than stars. And in southern Africa, the San (Bushmen) of the Kalahari called it the ‘Backbone of the Night’, picturing the sky as a great animal whose spine holds the heavens up, an image Carl Sagan made famous in his series Cosmos.

Regardless of the language and culture, you’ll notice that there’s almost always an unmistakable reference to a road, path or river, along with something to convey brightness, all of which is a clear nod to the appearance of the Milky Way in our night sky.