The pale arch of light from the plane of our galaxy can be a humbling sight on a clear, dark night. But it’s just a sliver of all the treasures lurking in the Milky Way. Dense clouds of interstellar dust block visible light from remote regions of the galaxy but allow longer wavelengths to pass through. In February, astronomers completed a new map of our galaxy as seen in submillimeter light, which is shorter than radio waves but longer than infrared waves.
Submillimeter light can penetrate dust clouds, revealing details at the center of the galaxy and in stellar nurseries not visible at other wavelengths. The map was produced by ATLASGAL, a project using the APEX telescope in northern Chile to map part of the Milky Way. The project charted one-third of the band of galactic light that encircles our solar system; the images below show a narrow slice toward the constellation Sagittarius. Combined with images from the Spitzer and Planck satellites, the ATLASGAL map (top row) creates a detailed atlas of some of the cold structures in our galaxy. Dust clouds in places like the Trifid and Lagoon nebulas (circled, left), both a few thousand light-years away, glow faintly, as do filaments of detritus in the center of the galaxy (circled, right), 28,000 light-years from Earth. At near-infrared wave-lengths (center row), these regions nearly vanish behind obscuring curtains of dust. The galactic center remains hidden in visible light (bottom row) as well, though hot stars in Trifid and Lagoon radiate pools of hydrogen gas, making them glow.
