The Sloan Digital Sky Survey-III (SDSS) has released the largest digital colour image of the sky ever made from millions of 2.8-megapixel images. The complete terapixel image would require 500,000 high definition TVs to view it at full resolution.

The SDSS has already provided a database of nearly half a billion objects including asteroids, stars, galaxies and quasars, but the latest release offers the most precise positions, colours and shapes for all of these objects and will provide opportunities for many new discoveries in the years to come.

“This is one of the biggest bounties in the history of science,” says Professor Mike Blanton from New York University, who is leading the data archive work in SDSS-III. “This data will be a legacy for the ages, as previous ambitious sky surveys like the Palomar Sky Survey of the 1950s are still being used today. We expect the SDSS data to have that sort of shelf life.”

The image began in 1998 using a 138 megapixel imaging detector on the 2.5 metre telescope at the Apache Point Observatory. That camera will now be retired and the focus of new surveys will be spectrometry, to determine distances to galaxies, and the temperatures and chemical compositions of stars. One such survey, the Baryon Oscillation Spectroscopic Survey (BOSS), will provide the largest three-dimensional galaxy map ever made and will help astronomers learn about the mysterious force of dark energy. “Dark energy i the biggest conundrum facing science today,” says BOSS Principal Investigator David Schlegel, “and the SDSS continues to lead the way in trying to figure out what the heck it is!”

In conjunction with the SDSS-III image release, astronomers working on SEGUE, the Sloan Extension for Galactic Understanding and Exploration, have also released the largest map of the outer Galaxy. “This map has been used to study the distribution of stars in our Galaxy,” says Connie Rockosi from the University of California, Santa Cruz, and the Principal Investigator of SEGUE. “We have found many streams of stars that originally belonged to other galaxies that were torn apart by the gravity of our Milky Way. We’ve long thought that galaxies evolve by merging with others; the SEGUE observations confirm this basic picture.”

SDSS-III is also operating two more surveys: MARVELS, which will implement a new instrument to measure spectra of 8,500 nearby Sun-like stars to look for 'wobbles' that will indicate the presence of a planet, and APOGEE, the APO Galactic Evolution Experiment, which uses an infrared spectrograph to undertake the first systematic study of stars in all parts of our Galaxy, even those on the other side of the central bulge.

The image released this week is free for all to download. “Astronomy has a rich tradition of making all such data freely available to the public, and we hope everyone will enjoy it as much as we have,” adds Bob Nichol, of the University of Portsmouth and Scientific Spokesperson for the SDSS-III collaboration.