J-PAS is the acronym of Javalambre PAU Astrophysical Survey. PAU is the acronym of Physics of the Accelerating Universe.

J-PAS will observe all the objects brighter than mag~22.5 over an area of more than 8000 square degrees. That includes billions of stars, hundreds of millions of galaxies, millions of quasars and AGNs, as well as thousands of variable objects such as supernovas and minor planets of the solar system.

The optical electromagnetic region comprises light with wavelengths between 4,000 Å and 7,000 Å roughly. The human eye can separate the optical light beams in three blocks, or filters: blue (4,000-5,300 Å), green (4,500-6,500 Å) and red (5,000-7,500 Å). The modern astronomical CCDs detect light between 3,500 Å and 10,000 Å, but they are not capable of measuring the wavelength of each beam of light. J-PAS has a camera and a filter system that will allow to decompose the the light of that wavelength range in 56 small blocks. This will provide J-PAS with exceptional capabilities in order to explore the spectra of astronomical objects. See the Survey Section for a more detailed description of the filter system.

Based on the area that we will target (8,000 to 9,000 square degrees), and the time that we have to complete the main astrophysical survey (5-6 years, depending on the performance of the instrument), we estimate that we will be able to detect astronomical objects down to an apparent magnitude (AB) of about 22.5. In terms of redshift, we will be able to observe galaxies up to z~1.3, emission-line galaxies up to z~2.5, quasars up to z~6, and supernovas up to z~0.6 . In the standard cosmological model (called the flat LambdaCDM model), the distance to z=1 is 3,300 Mpc, or 10.8 billion light-years, and the universe at z=1 was only 6 billion years old (it is about 13.7 billion years old now).

J-PAS is being built by partners from Spain and Brazil, and is staffed by researchers and engineers from those two countries, the U.S.A. and other European countries. A complete list of the participants can be found on the Collaboration webpage.

J-PAS will be conducted by a 2.5 m telescope at the OAJ (Observatorio Astronomico de Javalambre), which is located at the Pico del Buitre (Vulture Peak), in the Sierra de Javalambre (Javalambre Mountain Range), near Teruel, Spain. The site has a median seeing of 0.72'', and a high fraction of clear nights. It satisfies the IAU criteria for an astronomical site.