2MASS

2MASS, or the Two Micron All-Sky Survey, is a project that mapped the entire sky using infrared light. Unlike visible light, infrared can see through dust clouds in space, revealing stars, galaxies, and other celestial objects that are often hidden. Conducted between 1997 and 2001, 2MASS collected data on hundreds of millions of objects, creating a comprehensive catalog that helps astronomers study the universe's structure and composition. This survey has been vital for understanding star formation, galaxy distribution, and the universe's overall architecture.