Researchers today released the largest three-dimensional map of black holes and massive galaxies  yet produced, which pinpoints the locations and distances to more than 1 million galaxies. Most of those galaxies, each of which contains more than 100 billion stars, lie between 1 billion and 6 billion light-years from Earth. Mapping them will enable scientists to retrace the history of the universe for the last 6 billion years, the team says, thereby allowing astronomers to make better estimates for how much of it is composed of the "dark matter " that can’t be directly seen, and "dark energy ," the mysterious force that’s driving the expansion of the universe. The survey, which recently completed its second year, has so far covered about 8% of the sky. By the time the 6-year project is completed, researchers will have mapped all massive galaxies outside of the dust-clogged plane of our Milky Way galaxy that are visible from the Northern Hemisphere—altogether, about one-fourth of the sky that’s visible from Earth.
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