The most detailed map of the Milky Way to date shows 3.32 billion stars. It consists of more than 21,400 individual recordings and more than ten terabytes of data.

Tucson (United States). In the summer of 2022, the European Space Agency (ESA) published the most complete map of the Milky Way to date. The map shows about 1.8 billion stars and 156,000 smaller bodies such as exoplanets, moons, and asteroids. A map of the galaxy now published by the National Optical and Infrared Astronomy Research Laboratory (NSF’s NOIRLab) significantly outperforms the ESA map.

The map, which is publicly viewable in high resolution, contains about 3.32 billion celestial objects. It shows the galactic disk from the perspective of the southern hemisphere and contains about 6.5 percent of the night sky.

Map of 21,400 individual images
According to their publication in The Astrophysical Journal, astronomers created the necessary images over a two-year period with the Dark Energy Camera at NSF’s Cerro Tololo Inter-American Observatory in Chile. The map consists of a total of 21,400 individual images that were taken in the near-infrared and optical spectrum and together are more than 10 terabytes in size.

Because the recorded region of the Milky Way contains a large amount of dust that absorbs starlight, astronomers have had difficulty identifying faintly luminous objects. The images also contain light from cosmic nebulae, making it difficult to measure the brightness of individual objects. In addition, the area contains a large number of stars that are barely distinguishable in the different images. Stars partially overlap in the images, making it difficult to tell what’s in the background and what’s in the foreground.

3.32 billion stars
Despite these problems, astronomers were able to clearly identify 3.32 billion stars, creating the most comprehensive celestial atlas of the Milky Way. As Andrew Saydjari of the Harvard-Smithsonian Center for Astrophysics (CfA) explains, this was possible because the scientists mapped a particularly star-rich region of the galaxy.

The near-infrared camera allows them to see through most of the dust. Also helpful was a new data-processing method that, according to The Astrophysical Journal, makes it possible to predict what’s behind a star. The astronomers were thus able to calculate how dense star clusters and cosmic nebulae change the images, thus improving the accuracy of the map.