What is the approximate diameter of the Milky Way's disk in light-years?

The Milky Way’s visible disk is approximately 100,000 light-years in diameter. A light-year is the distance light travels in one year—about 9.46 trillion kilometres—so the galaxy’s stellar disk spans an almost unimaginable distance.

This measurement describes the broad, observable disk containing most of the Milky Way’s stars, gas, and dust. It does not include the full dark-matter halo, which extends vastly farther into space. Nor does it mean the galaxy has a sharp physical edge: the density of stars gradually decreases with distance, making the exact diameter depend on how astronomers define the boundary.

The Milky Way’s disk is relatively thin compared with its width, although it includes a thicker stellar component and is warped near its outskirts. The central region contains a barred bulge, while spiral arms wind through the disk. The Sun sits roughly 26,000 light-years from the center, so Earth is located well away from the crowded and energetic galactic core.