The Milky Way
Every other galaxy on this site we see from the outside, as a distant island. The Milky Way is the one we live inside — and that changes everything. We can't photograph it from afar, we can only look out through it. But that also makes it the one galaxy you can see in genuine glory with your own eyes: the pale river of light arching across a truly dark sky is our galaxy, seen edge-on from within.
Image: EHT Collaboration. The heart of our galaxy: Sagittarius A*, the four-million-solar-mass black hole around which the entire Milky Way turns, imaged in 2022. It sits about 27,000 light-years from us, toward the constellation Sagittarius.
A barred spiral we can't step out of
The Milky Way is a barred spiral galaxy — a flat disk about 100,000 light-years across, holding somewhere between 100 and 400 billion stars, with a straight bar of stars through its central bulge and spiral arms winding outward. The Sun sits in a minor arm, roughly 27,000 light-years from the center — about two-thirds of the way out, in the galactic suburbs. We take about 225 to 250 million years to complete one orbit of the galaxy; the last time the Sun was in its current spot, dinosaurs were just appearing. One trip around is called a "galactic year," and the Sun has made only about 20 of them in its whole life.
Diagram by Michael Paycer (edge-on, schematic). "Milky Way" names both the galaxy and the band of light it makes in our sky — they're the same thing, seen from inside.
The monster at the center
At the very center of the galaxy, hidden behind thick dust, lies Sagittarius A* — a supermassive black hole with the mass of about four million Suns. The entire galaxy, all those hundreds of billions of stars, orbits this dark anchor. We know its mass with remarkable precision because we've tracked individual stars whipping around it for decades, and in 2022 the Event Horizon Telescope finally imaged its shadow. It's a quiet giant now, sipping rather than gorging on gas — which is part of why our galaxy is a calm, livable place. The full story of what it is lives in the Black Holes section; here it's enough to know that our home galaxy turns around a black hole.
The one galaxy you can actually see
Here's the beautiful inversion. Every other galaxy is a faint smudge that disappoints at the eyepiece — but your own galaxy is a naked-eye spectacle, no telescope required. On a truly dark, moonless night, far from city lights, the Milky Way rises as a glowing band of soft light stretching from horizon to horizon, mottled with dark rifts of dust. That light is the combined glow of billions of stars in the disk you're sitting inside. The catch is dark skies: from a city, light pollution erases it completely, which is why most people alive today have never seen it. The summer months, looking toward rich star-clouds of Sagittarius (the direction of the galaxy's center), give the best view from the Northern Hemisphere. No equipment beats your own eyes and a dark site — see how to observe for finding one. It is, quite literally, the only way to see a galaxy as it truly is.
From "spilled milk" to a wheel of stars
Nearly every culture has a story for the glowing band. The name comes from the Greek galaxías kýklos, "milky circle" — in myth, milk spilled from the goddess Hera across the sky. But its true nature was a mystery until 1610, when Galileo turned his new telescope on it and discovered the band was not a cloud at all but countless individual stars, too faint and crowded to separate by eye. It was one of the first things his telescope revealed, and one of the first hints that the universe was vastly bigger and richer than it looked. Every dark-sky glimpse of the Milky Way is a look at Galileo's discovery — a haze that is really a multitude.
"The Milky Way is nothing else but a mass of innumerable stars planted together in clusters."
— Galileo Galilei, Sidereus Nuncius (1610), on first resolving the band with a telescope
Galaxy Types · Galaxy Collisions · Sagittarius A* · Andromeda · Galaxies Hub · How to Observe · Glossary
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