Images of the northern and southern hemispheres of our galaxy (bottom) reveal “walls” of galaxies that are the largest known structures in the universe. Zooming in on a patch of sky in the southern hemisphere reveals the spiral galaxy M33 (top left). Zooming in further (top centre) reveals a region of intense star formation known as NGC 604 (green swirls, top right) (Image: M. Blanton and SDSS-III)

It would take 500,000 high-definition TVs to view it in its full glory. Astronomers have released the largest digital image of the night sky ever made, to be mined for future discoveries.

It is actually a collection of millions of images taken since 1998 with a 2.5-metre telescope at Apache Point Observatory in New Mexico. The project, called the Sloan Digital Sky Survey, is now in its third phase, called SDSS-III.

Altogether, the images in the newly released collection contain more than a trillion pixels of data, covering a third of the sky in great detail.


“This is one of the biggest bounties in the history of science,” says SDSS team member Mike Blanton of New York University in New York City. “This data will be a legacy for the ages.”

Biggest 3D map

Data released previously by the survey has already led to many advances, including the discovery of tiny, dim galaxies orbiting the Milky Way, and maps of the large-scale structure of the universe.

The third phase of the survey started in 2008. It is now focusing on measuring the light spectra of objects seen in the huge image.

One project within the survey aims to measure spectra for more than a million galaxies. These spectra reveal how far away the galaxies are, and by measuring so many of them, astronomers will create the biggest 3D map of the universe yet. Analysing the map will allow them to probe the nature of the mysterious dark energy that is thought to be accelerating the expansion of space.

Another SDSS-III project will take spectra of thousands of stars to discover planets and brown dwarfs in orbit around them.

You can browse images from SDSS here. The results were announced on Tuesday at a meeting of the American Astronomical Society in Seattle, Washington.