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At the 217th meeting of the American Astronomical Society, underway in Seattle, the Sloan Digital Sky Survey-III (SDSS-III) team has made publicly available the largest ever digital image of the sky. It's a mosaic of millions of 2.8 megapixel images, taken between 1998 and 2010 at the Apache Point Observatory in New Mexico, USA.
Approximately 35% of the sky is covered, and the amount of information contained in the image is such that both details of individual objects, and their large scale distribution, can be studied, as shown in the figure above.
To give some idea of the resolution of the image, it would need a screen with an area equal to half a million high definition televisions to view the full image at 100%.
The study of such a quantity of information, made available to everyone, will surely produce new discoveries to be added to the list of those already made by the research team, that have been carrying out the various phases of the survey since the nineties. About half a billion celestial objects have been discovered by the SDSS-III, including asteroids, stars, galaxies and quasars. For a large number of these objects it has also been possible to determine the precise position and colour, and for the galaxies, their shape.
The camera that produced the gigantic mosaic has now been retired, and since 2009 the survey instruments have been significantly upgraded. This will help researchers in the task of realising, by 2014, a new map of the Universe, but this time in 3-D. This spectroscopic survey, is, in fact, already underway, and will give the distances to the galaxies contained in the 2-D map.
Two projects connected to the new survey, the Sloan Extension for Galactic Understanding and Exploration and the APO Galactic Evolution Experiment, will study the distribution and proper motions of the stars in our galaxy. The objective is to identify the various stellar flows in order to understand the origin of those galactic components that come from the merger of small external systems that collided with our own.
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