Washington: Astronomers have come up with the largest ever 3D map of the sky, encompassing massive galaxies and distant black holes, based on Sloan Digital Sky Survey III (SDSS-III).
The new map pinpoints the locations and distances of over a million galaxies. It covers a total volume equivalent to that of a cube four billion light-years on one side.
"We want to map the largest volume of the universe yet, and use that map to understand how the expansion of the universe is accelerating," said Daniel Eisenstein from the Harvard-Smithsonian Centre for Astrophysics, the director of SDSS-III.
The map is the centrepiece of Data Release 9 (DR9), which publicly releases the data from the first two years of a six-year survey project.
The release includes images of 200 million galaxies and spectra of 1.35 million galaxies, according to a Harvard-Smithsonian statement with SDSS-III.
Spectra take more time to collect than photographs, but provide the crucial third dimension by letting astronomers measure galaxy distances.
"Our goal is to create a catalogue that will be used long after we are done," said Michael Blanton of New York University, who led the team that prepared Data Release 9.
The release includes new data from the ongoing SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), which will measure the positions of massive galaxies up to six billion light-years away, as well as quasars - giant black holes actively feeding on stars and gas - up to 12 billion light-years from earth.
BOSS is targeting these big, bright galaxies because they live in the same places as other galaxies and they are easy to spot.