The largest and most inclusive survey of the heavens ever undertaken captured its first light earlier this month. The $80 million project, called the Sloan Digital Sky Survey, will gather images of perhaps 200 million celestial objects and map the precise positions of a million galaxies in a 1.5-billion-light-year-wide chunk of the universe.
Crucial to the survey is a sophisticated camera designed and built by a team led by James Gunn of Princeton University. Group members confirm that the camera, which can take in a swath as wide as the Big Dipper's bucket in a single image, has been successfully mated to the 2.5-meter Sloan Telescope at Apache Point, New Mexico, and has made its first images of the night sky. The group isn't discussing its initial data any further until an 8 June press conference at the American Astronomical Society meeting in San Diego.
In the works for years, the Sloan survey involves researchers at seven universities and research institutions in the United States and a collaboration called the Japan Participation Group. After a 1-year commissioning period, the project will spend about 5 years collecting images of celestial objects, in five different colors, by letting the night sky rotate past the camera's huge array of 54 charge-coupled devices. The survey will cover about a quarter of the northern sky and selected slices in the south. The team will also select the million brightest galaxies for a closer look. By analyzing the galaxies' light, the astronomers will determine their "redshifts"--wavelength shifts indicating the galaxies' approximate distances from Earth.
The redshift survey will reveal in exquisite detail the filaments, clumps, voids, and walls traced out by the galaxies over vast reaches of space. "I'm looking forward to seeing what the universe looks like," says Adrian Melott, a cosmologist who studies large-scale structure at the University of Kansas, Lawrence. "I wish them luck."