twomass

Two Micron All-Sky Survey (2MASS) was an astronomical survey that mapped the entire sky in the near-infrared, providing uniform photometry in three bands. The project aimed to create a comprehensive, accessible catalog of celestial sources to support studies of Galactic structure, star formation, and distant galaxies.

Observations were conducted from 1997 to 2001 using two 1.3-meter telescopes, located at Mount Hopkins, Arizona, and Cerro Tololo Inter-American Observatory in Chile. A near-infrared camera captured data in J (1.25 μm), H (1.65 μm), and Ks (2.16 μm) bands, chosen for good atmospheric transmission and astrophysical relevance. The survey produced calibrated, all-sky data suitable for statistical analyses and object identification.

The data products include the All-Sky Point Source Catalog (PSC) and the All-Sky Extended Source Catalog (XSC). The PSC lists hundreds of millions of point-like sources, while the XSC contains a few million resolved, extended objects such as galaxies. Photometry and astrometry across the three bands were homogenized, enabling reliable color measurements and cross-matching with other surveys.

2MASS has had a lasting impact on astronomy, enabling studies of the Milky Way’s structure, the census of low-mass stars and brown dwarfs, and large-scale extragalactic research. The datasets are publicly accessible through the Infrared Science Archive (IRSA) at NASA/IPAC, and are routinely used in conjunction with optical surveys to enhance source identification and characterization.