2MASS

The Two Micron All-Sky Survey, or 2MASS, was an astronomical survey of the whole sky in infrared light. It took place between 1997 and 2001, in two different locations: at the U.S. Fred Lawrence Whipple Observatory on Mount Hopkins, Arizona, and at the Cerro Tololo Inter-American Observatory in Chile, each using a 1.3-meter telescope for the Northern and Southern Hemisphere, respectively. It was conducted in the short-wavelength infrared at three distinct frequency bands (J, H, and K) near 2 micrometres, from which the photometric survey with its HgCdTe detectors derives its name.

2MASS produced an astronomical catalog with over 300 million observed objects, including minor planets of the Solar System, brown dwarfs, low-mass stars, nebulae, star clusters and galaxies. In addition, 1 million objects were cataloged in the 2MASS Extended Source Catalog (2MASX). The cataloged objects are designated with a "2MASS" and "2MASX"-prefix respectively.