Sloan Digital Sky Survey Changes the Face of Astronomy
By Steve Koppes
Other collaborations look to us to see how we’ve done it.”
Professor in Astronomy, Astrophysics
Two hundred and seventy two stars gave their lives for the photo spread on cosmic explosions that graced pages 80 and 81 of the March 2007 National Geographic.
Ben Dilday, University graduate student in Astronomy & Astrophysics, assembled these images of exploding stars from observations the Sloan Digital Sky Survey collected in 2005 and 2006. The images come in the vanguard of the SDSS II (Sloan Digital Sky Survey’s Phase Two), which focuses, in part, on supernovas. During its first phase, survey astronomers invented a new way of doing astronomy by dedicating a single telescope to mapping the universe in three dimensions.
The SDSS began taking data in 1998, following years of planning by scientists at Chicago and elsewhere. The planners include Donald York, the survey’s founding director and the Horace B. Horton Professor in Astronomy & Astrophysics, and current director Richard Kron, Professor in Astronomy & Astrophysics.
“Everybody said we were crazy,” York recalled. But now, added Kron: “Other collaborations look to us to see how we’ve done it.”
Today, the SDSS collaboration consists of 300 scientists at 25 institutions worldwide. The University has played a continuous role in the survey’s management throughout its history.
Fermi National Accelerator Laboratory joined the SDSS collaboration early on. The Fermilab involvement expanded pre-existing connections that culminated in 2006 in a major new role for the University in managing the laboratory for the U.S. Department of Energy.
The SDSS collaboration built a 2.5-meter telescope for its survey, but even that relatively modest size once seemed an outlandish commitment of hardware to a single sky survey. Now, more than 20 universities, national laboratories and private organizations have banded together to propose the Large Synpotic Survey Telescope. Measuring 8.4 meters, the telescope would “provide digital imaging of faint astronomical objects across the entire sky, night after night,” according to the LSST Web site.
Other observatories, including the Hubble and Spitzer space telescopes, have gradually increased the amount of survey time allocated to surveys. “It had to be done first on a smaller telescope, such as our two- and one-half meter diameter telescope,” York said.
Astronomers still do targeted studies of a small number of objects in search of answers to specific questions. But now they also sweep the skies for all the data their instruments can collect and sort through it later. “It’s a sea change,” York said.
Large collaborations, such as LSST and SDSS, enable participating institutions to combine their talents and resources. Chicago’s early responsibilities included integrating the survey’s spectroscopic pipeline from components contributed by a variety of institutions and helping to build a sophisticated camera for the telescope.
The pipeline consists of software that processes SDSS data to identify spectral lines of chemical elements. Overseeing the integration of that pipeline was Joshua Frieman, Professor in Astronomy & Astrophysics. More recently, he led the effort to refocus the SDSS on a small part of the sky to look for supernovas.
Frieman now leads the Chicago component of the Dark Energy Survey collaboration. That effort, like SDSS II, seeks to measure the mysterious force causing the universe to fly apart. “The Dark Energy Survey is going to build upon the experience of the Sloan Digital Sky Survey,” Kron said.