Two Micron All Sky Survey

Two Micron All Sky Survey
IPAC/Caltech, by Thomas Jarrett · Public domain · source
Name	Two Micron All Sky Survey
Acronym	2MASS
Mission type	Astronomical survey
Operator	University of Massachusetts Amherst; Infrared Processing and Analysis Center
Launch	Ground-based
Wavelength	Near-infrared (J, H, Ks)
Telescopes	Fred Lawrence Whipple Observatory 1.3 m; Cerro Tololo Inter-American Observatory 1.3 m
Start	1997
End	2001
Catalog	Point Source Catalog; Extended Source Catalog

Two Micron All Sky Survey. The Two Micron All Sky Survey was a ground-based near-infrared astronomical survey that mapped the entire sky at 1.25 μm, 1.65 μm, and 2.17 μm, producing comprehensive catalogs used across contemporary astronomy and astrophysics. Initiated by teams at the University of Massachusetts Amherst and the Infrared Processing and Analysis Center, it operated from twin 1.3 m telescopes at the Fred Lawrence Whipple Observatory and Cerro Tololo Inter-American Observatory, yielding datasets foundational for studies involving the Milky Way, Andromeda Galaxy, Magellanic Clouds, and extragalactic structure.

Overview

2MASS undertook uniform near-infrared imaging to overcome extinction in the Galactic Center, enabling detection of brown dwarfs, T Tauri stars, and obscured star clusters missed by optical surveys such as the Palomar Observatory Sky Survey and the Sloan Digital Sky Survey. The project produced the Point Source Catalog and Extended Source Catalog that served as reference frames for missions including Spitzer Space Telescope, Wide-field Infrared Survey Explorer, Gaia, and James Webb Space Telescope. Principal investigators and collaborators included researchers affiliated with University of Massachusetts Amherst, California Institute of Technology, NASA, and the National Optical Astronomy Observatory.

Survey Design and Instrumentation

The survey design balanced sky coverage, sensitivity, and angular resolution using twin 1.3 m telescopes equipped with identical infrared camera systems incorporating HgCdTe arrays developed with support from NASA and partners at the Jet Propulsion Laboratory. The detectors provided simultaneous imaging in the J, H, and Ks bands, allowing color-color selection techniques applied to find L dwarfs, T dwarfs, and heavily reddened protostars. Observing strategies accounted for atmospheric transmission at Cerro Tololo and Mount Hopkins sites, leveraging standard star networks tied to photometric systems used by UKIRT and the Infrared Space Observatory calibrations. The project coordinated scheduling and operations with staff from Smithsonian Astrophysical Observatory and used pipelines developed in collaboration with the Massachusetts Institute of Technology and the Space Telescope Science Institute.

Data Processing and Catalogs

Raw data were processed through an automated pipeline at the Infrared Processing and Analysis Center, involving flat-fielding, sky subtraction, astrometric calibration against catalogs such as the Hipparcos Catalogue and later cross-matches with Tycho, and photometric calibration using standard stars associated with the CIT photometric system. The resulting Point Source Catalog contained hundreds of millions of detections allowing studies of globular clusters like Omega Centauri and 47 Tucanae, and the Extended Source Catalog provided homogeneous photometry for nearby galaxies including the Sculptor Galaxy and Triangulum Galaxy. Cross-identifications with surveys such as IRAS, FIRST, NVSS, and ROSAT enabled multiwavelength analyses linking active galactic nuclei in Seyfert galaxies and quasars to infrared properties. Data release events were coordinated with archives at the National Aeronautics and Space Administration and the European Southern Observatory.

Scientific Results

2MASS data contributed to the discovery and spectral classification of substellar objects, including early identifications of Gliese 229B-like companions and numerous L dwarf and T dwarf populations, informing models of brown dwarf atmospheres and cooling tracks. The survey revealed the stellar mass distribution in the disk and bulge of the Milky Way, refining measurements of the Galactic center stellar density and the structure of the Local Group. Infrared-selected galaxy samples improved estimates of the Hubble Constant via Tully–Fisher relation studies and supported large-scale structure mapping that connected with results from the 2dF Galaxy Redshift Survey and the Sloan Digital Sky Survey. 2MASS also enabled identification of obscured young stellar objects in complexes like Orion Nebula, Taurus Molecular Cloud, and Rho Ophiuchi, linking infrared excesses to disk evolution and planet formation studies pursued by teams at Caltech and Harvard–Smithsonian Center for Astrophysics.

Legacy and Impact

The 2MASS catalogs remain a fundamental resource for target selection and cross-calibration for modern facilities such as ALMA, Chandra X-ray Observatory, Hubble Space Telescope, and the Large Synoptic Survey Telescope (now Vera C. Rubin Observatory). Techniques pioneered in 2MASS pipelines influenced data handling for missions like WISE and the Euclid mission, while its all-sky coverage underpins citizen science projects hosted by the Zooniverse and professional analyses in institutions such as Max Planck Institute for Astronomy and Kavli Institute for Cosmological Physics. The survey fostered collaborations spanning NASA, NSF-funded observatories, and international partners in Chile, Argentina, and Australia, leaving an enduring impact on studies of stellar evolution, extragalactic astronomy, and the infrared sky.

Category:Infrared astronomy Category:Astronomical surveys Category:Catalogs (astronomy)