Press Release

Journalists invited to attend Sloan Digital Sky Survey Symposium Aug. 15-18

By SpaceRef Editor
July 30, 2008
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An international symposium, “The Sloan Digital Sky Survey: Asteroids to Cosmology,” will be held Friday, Aug. 15 to Monday, Aug. 18 at the Merchandise Mart Conference Center in downtown Chicago. The University of Chicago’s Kavli Institute for Cosmological Physics will host the event.

Journalists can register free for the meeting; see information below.

The Sloan Digital Sky Survey (SDSS-I, 2000-2005, and SDSS-II, 2005-2008) has transformed many fields of astronomy, with deep digital imaging of one-quarter of the sky, the largest three-dimensional maps of cosmic structure and the outer Milky Way Galaxy, and the discovery of more than 500 supernovae for precisely measuring the expansion of the universe and the global gravitational effects of dark matter and dark energy.

Symposium participants will review progress and prospects in these fields, including contributions from the SDSS and other major surveys. General information about the symposium, including a list of review speakers, is available at

There are several remaining spaces for journalists at the symposium, which will be distributed on a first-come basis. For more information, contact Steve Koppes at or 1-773-702-8366.

Program summary & preview of likely news higlights

The Symposium begins with a session on galaxies, a field that the SDSS has completely transformed with its enormous statistical samples of high quality data. The news highlight may be Steven Bamford’s talk on science results from The Galaxy Zoo (, which is probably the largest collaborative science project in history. More than 100,000 members of the general public have visually classified SDSS images of galaxies into spiral and elliptical categories (a task at which humans still outperform automated methods), with a total of more than 30 million classifications. Bamford’s talk will present the relations between galaxy morphology, color, and environment, revealing some surprising new trends.

Adam Bolton will present results from the Sloan Lens Advanced Camera for Surveys (SLACS) survey, which uses spectacular Hubble Space Telescope images of 70 gravitationally lensed Einstein rings (see for examples) to measure the distribution of dark matter around the most massive galaxies in the universe. A poster presentation by Huan Lin will highlight remarkable new examples in which very distant galaxies (redshift 2-4) are strongly magnified by lensing from foregroound galaxies or clusters, enabling detailed studies of young galaxies that would be impossible without the assistance of graPlevitational telescopes.

A central theme of the Galaxies session will be understanding the dichotomy between star-forming galaxies and “passive” (a.k.a. “red-and-dead”) galaxies, combining the SDSS survey of the local universe with other surveys that probe deeper into the past, most notably the Keck telescope’s DEEP-2 survey led by invited review speaker Sandra Faber. Current theories tie the origin of this dichotomy to the action of supermassive black holes at galaxy centers, and evidence for and against this idea will be critically examined in the talks and discussions.

The SDSS has discovered the majority of the world’s known quasars, especially the rare high-redshift quasars that show that supermassive black holes a billion times more massive than the sun had already formed when the universe was less than one-tenth of its current age. A central theme of the Quasars session will be understanding what causes some of these black holes to grow rapidly and shine with enormous luminosity, while at any given time the majority remain dormant at the centers of their host galaxies. Clues to the mechanisms that feed black hole growth come from the overall rise and fall of the quasar populations detected at visible, X-ray, and infrared wavelengths, from direct observations of their galactic hosts, and from the spatial clustering of quasars, which in turn tells about the dark matter halos in which they reside.

On a different theme, Naohisa Inada’s talk on gravitational lenses will discuss both the rare, remarkable, wide-separation lenses uncovered by the SDSS and the cosmological conclusions from the systematic search for lensed quasars in the SDSS.

Although the SDSS was originally designed as a survey of the distant universe, it also produced major discoveries about the Milky Way Galaxy, its nearest neighbors, and its populations of stars. The SDSS has so far detected nine new dwarf satellite companions of the Milky Way, equal to the number found in the preceding seven decades despite searching only 20% of the sky (see Star maps from the SDSS show that complex structure is ubiquitous in the outer Galaxy, suggesting that the Galaxy’s stellar halo has been built up largely by accreting and shredding other dwarf companions (see and

These discoveries inspired SEGUE (the Sloan Extension for Galactic Understanding and Exploration), one of the three projects that comprise SDSS-II. Galactic substructure will be the central theme of the Milky Way session on Saturday, August 16, including theoretical predictions based on cold dark matter models of galaxy formation, presented by review speaker Kathryn Johnston, and the results of searches for structure in the new SEGUE data by Heidi Newberg and Kevin Schlaufman. Gerry Gilmore will discuss the properties of dwarf satellites, as measured by the SDSS and by follow-up observations from large telescopes: these smallest galaxies provide new tests of the nature of dark matter and the physical processes that govern galaxy formation.

Likely highlights of the Stars session on Saturday afternoon include the patterns of chemical elements in the Galaxy’s oldest stars (in talks by Tim Beers and David Lai). Because these atoms were themselves formed in some of the first supernova explosions in the cosmos, these patterns provide archeological evidence about the nature of the earliest stars.

With 3-dimensional galaxy maps of unprecedented size and detail, the SDSS has turned measurements of large scale galaxy clustering into a precision tool for determining the parameters of the universe and testing theoretical descriptions of galaxy formation. Talks in the Large Scale Structure session on Sunday, August 17, will include preliminary measurements from the final SDSS galaxy maps (observations for which concluded in May).

One of the signature achievements of the SDSS has been the detection of baryon acoustic oscillations (BAO), a subtle excess of galaxy pairs at large separations caused by sound waves that travel in the early universe, and the use of BAO as a “standard ruler” to measure the expansion of the universe (see

The Sunday talks will include new constraints on cosmic acceleration and the geometry of space from more precise BAO measurements, new determinations of the amount of dark matter and the strength of its clustering from combinations of galaxy clustering and weak gravitational lensing, and constraints from dark matter clustering in the high-redshift universe inferred from the structure of absorbing gas along the line of sight to background quasars. A central theme of discussion in this session and in the Supernova Cosmology session on Monday will be whether the ever-improving cosmological measurements remain consistent with the simplest explanation for the accelerating expansion of the universe, Einstein’s cosmological constant, or whether they instead suggest that the properties of the dark energy driving the acceleration have changed over time.

In addition to mapping 1/4 of the sky, the SDSS has carried out repeated scans of a 100-degree long (2.5-degree wide) stripe over the course of eight years. By detecting and characterizing moving objects in this stripe, the SDSS has made unique contributions to understanding the population of asteroids and more distant Kuiper Belt Objects in our solar system.

The likely press highlight of the Solar System session on the morning of Monday, August 18 will be announcement of the discovery (by SDSS astronomer Andrew Becker) of a remarkable object that is currently about the same distance from Earth as the planet Uranus but whose 27,000-year orbit carries it to more than 70 times that distance. This object is akin to the famous dwarf planet Sedna, but its orbital properties are considerably more extreme, with a much more elongated path that takes it nearly twice as far from the Sun.

The Supernova Cosmology session features invited speakers from the Carnegie Supernova Project (Wendy Freedman), the CFHT Supernova Legacy Survey (Mark Sullivan), and the SDSS-II Supernova Survey (Josh Frieman). These are, respectively, the largest samples of well observed supernovae in the nearby universe, the distant universe, and the intermediate redshifts that connect them, and together they constitute a major step forward in the quest to determine the nature of dark energy. In addition to presenting the latest cosmological constraints from these ambitious projects, including the first results from the final SDSS-II data set, a focus of the talks and discussion will be the systematic uncertainties in using supernovae to make high-precision measurements of cosmic acceleration, and methods to control those uncertainties. With NASA and DOE preparing to invest more than half-a-billion dollars in a dark energy space mission, this discussion comes at a critical time.

Alongside its individual science discoveries, the SDSS has transformed the culture of astronomy, showing what can be achieved when large teams of astronomers pool resources and expertise to produce enormous, high-quality, public data sets, which have a broad range of science applications. This global impact of the SDSS, an underlying theme throughout the Symposium, will be especially evident in the final session, with talks on three of the main near-term successors to SDSS-I and SDSS-II.

Pan-STARRS ( is just beginning operations in Hawaii, using a giant mosaic camera to carry out an imaging survey that will be deeper than the SDSS imaging survey and will cover more of the sky, including repeated imaging of selected areas of sky to detect near-earth asteroids, outer solar system objects, and distant supernovae.

The Dark Energy Survey ( is constructing a giant mosaic camera that will be used to carry out a deep, large-area imaging survey in the southern hemisphere, probing the nature of dark energy with galaxy clusters, weak gravitational lensing, large scale galaxy clustering, and supernovae.

SDSS has served as a test bed for the science to be pursued with the much more ambitious Large Synoptic Survey Telescope project a part of a talk by the University of Washington’s Ivezic Zeljko (this talk takes place during the Solar System session on the morning of the last day of the conference).

Finally, SDSS-III ( is a program of four spectroscopic (as opposed to imaging) surveys that will use the Sloan survey telescope and upgraded or new instruments to make high-precision cosmic distance measurements with baryon acoustic oscillations, to map the structure and history of the Milky Way Galaxy, and to reveal the architecture of giant planet systems. SDSS-III will begin operations on July 15, 2008, and it is expected to continue through mid-2014.

The conference summary will be given by Jim Gunn, who, as Project Scientist, has guided the SDSS through nearly two decades of construction, operation, and scientific achievement.

SpaceRef staff editor.