Mapping The Milky Way In Three Dimensions

By measuring the distance from our sun to thousands of individual pulsating stars scattered across the Milky Way, researchers have charted our Galaxy on a larger scale than ever before.

Their new three-dimensional map, which provides a broad view of our place among the stars, reveals the S-like structure of the Milky Way’s warped stellar disc. “Our map shows the Milky Way disk is not flat. It is warped and twisted,” says co-author Przemek Mroz in a related video. “This is the first time we can use individual objects to show this in three dimensions.” Much of the current understanding of the spiral shape and structure of our Galaxy is built upon indirect measurements to celestial landmarks and inferences based on other galaxies in the Universe.

However, the Galactic map drafted by those limited observations remains incomplete. Like so many lighthouses on distant foggy shores, classical Cepheid variable stars – massive young stellar bodies that burn hundreds, if not thousands of times brighter than our own Sun – pulsate at regular intervals and are visible through the vast clouds of interstellar dust that often obscure dimmer stellar bodies. Using the periodic variations in their brightness, the distances to these stars can be precisely determined. Dorota Skowron and colleagues charted the distance to more than 2,400 Cepheids throughout the Milky Way, most of which were identified by the Optical Gravitational Lensing Experiment (OGLE) – a project that more than doubled the number of known Galactic classical Cepheids.

By determining the 3D coordinates of each distant pulsing star relative to our Sun, Skowron et al. built a large-scale 3D model of the Milky Way galaxy. The new map illustrates and helps constrain the previously observed shape of the Galaxy’s warped stellar disc.