The Sloan Digital Sky Survey, of which the University of Washington is part, will soon see the entire sky, and even peer into the Milky Way’s galactic center.
The sky survey, called SDSS for short, is a multi-institution group of astronomers who since 2000 have searched the skies with the 100-inch, wide-angle optical telescope at the Apache Point Observatory in New Mexico.
“We have mapped the large-scale structure of the universe, traced out previously unknown structures in the Milky Way, and made unanticipated discoveries from asteroids in our own solar system to the most distant quasars,” said Michael Blanton, an astrophysicist with New York University and director of the new phase of the survey.
Now, the group is adding a second participating telescope high in the Chilean Andes, and a program using an innovative technology — aided by UW engineers — to observe and make detailed maps of thousands of previously unstudied nearby galaxies.
“The SDSS has observed more than half a million Milky Way stars over the past 14 years, which I call a good start,” said Jennifer Johnson, astronomer at The Ohio State University and the scientific spokesperson for the project. “However, from the Northern Hemisphere, the Earth blocks our view of a quarter of the Milky Way, and mostly obscures our view of the galactic center.”
Completing that picture will be the Irénée du Pont Telescope at Las Campanas Observatory in Chile, home to the clearest skies on the planet. The second telescope will also study stars in the nearby Magellanic Clouds, giving astronomers a better understanding of the Milky Way’s immediate neighborhood.
The sky survey’s new program, dubbed SDSS-IV, is a set of three surveys involving a collaboration of 200 astronomers across 40 institutions and four continents. The work is made possible in part by a new technique of bundling sets of fiber-optic cables into tightly-packed arrays. These collect light from across an entire galaxy, enabling detailed measurements of more than 10,000 nearby galaxies at 20 times the rate of previous surveys.
Staff and students in the UW Astronomy Department, led by research scientist Nick MacDonald, are active in the design, engineering and testing of the innovative fiber-optic arrays.
The new surveys will enable astronomers to:
- Explore the compositions and motions of stars across the entire Milky Way in unprecedented detail.
- Measure the expansion of the universe during a poorly understood five-billion-year period of the universe’s history.
- Make detailed maps of the internal structure of thousands of nearby galaxies to learn how they have grown and changed over billions of years.
Another program in this new phase will follow up on objects whose light output varies with time.
“Such investigations discover and characterize a menagerie of astrophysical extremes,” said Scott Anderson, UW Astronomy Department chair and co-lead on that survey, joined by researchers from other participating institutions and assisted by UW graduate student John Ruan.
“These range from flaring or pulsating single stars and binary star systems in our own Milky Way to luminous quasars powered by material spiraling into supermassive black holes at the centers of distant galaxies.”
The UW was among the first eight members of the sky survey group. The telescope, optics and buildings at the Apache Point Observatory were designed at the UW. Former UW astronomer Bruce Margon, now with the University of California, Santa Cruz, was the survey’s first scientific director.
Margon’s words when the sky survey began are no less true today. Calling it “an encyclopedia of the sky,” he added, “the possible projects resulting from the information are never-ending.”
Funding for the Sloan Digital Sky Survey IV has been provided by the Alfred P. Sloan Foundation and the participating institutions.
- Watch “The SDSS at Night,” a video by John Parejko of Yale University and the Sloan Digital Sky Survey collaboration. Workers are seen working on and studying the heavens with the Sloan Foundation Telescope at Apache Point Observatory, Sunspot, New Mexico.