New Effort to Learn How Our Galaxy Formed Makes Public Release of Its First Data

This map shows an infrared view of the Milky Way, as seen from Earth, plus the infrared spectra of two stars. Green circles show locations where infrared spectroscopy data were obtained during the first year of Sloan Digital Sky Survey-III observations with the Apache Point Observatory Galactic Evolution Experiment (APOGEE). The white boxes show the infrared spectra of two stars as seen by APOGEE; the red lines show where these stars live in the Galaxy. One of these stars is in the galactic bulge, which is rich in elements heavier than hydrogen, and one is further out in the galactic disk, which has fewer such heavy elements. Credit: Peter Frinchaboy (Texas Christian University), Ricardo Schiavon (Liverpool John Moores University), and the SDSS-III collaboration. Infrared sky image from 2MASS, IPAC/Caltech, and University of Massachusetts.

Scientists with the Sloan Digital Sky Survey III (SDSS-III), including Penn State University astronomers, have released a new online public data set featuring 60,000 stars that are helping to reveal how our Milky Way galaxy formed.

"This data set is unprecedented for investigating the history and structure of our Galaxy, as well as nearby low-mass stars," said Penn State Assistant Professor of Astronomy and Astrophysics Suvrath Mahadevan, one of the SDSS-III scientists.

The highlight of this SDSS-III "Data Release 10" is a new set of high-resolution measurements of the amount of infrared light given off by each star at each wavelength. The scientists used infrared light, which is invisible to human eyes, because this light is able to penetrate the veil of dust that obscures the center of the Galaxy. This light-blocking barrier limited the ability of previous studies to consistently reveal information about the stars in the Milky Way that were hidden behind the dust.

The new infrared detections are made possible by a new SDSS-III instrument that is part of an effort to create a comprehensive census of our Milky Way galaxy -- the SDSS-III's Apache Point Observatory Galactic Evolution Experiment (APOGEE). The new spectra are the first data to be released by the APOGEE project, which is led by Steven Majewski of the University of Virginia. "The APOGEE instrument was designed for observing the infrared light from these hidden stars in our Galaxy," explained Mahadevan. "This innovative instrument can obtain spectra of 300 stars in a single observation. Our goal is to obtain detailed information on approximately 100,000 stars during the three-year span of the APOGEE survey."

The question of how our Milky Way galaxy formed has been the subject of scientific speculation and debate for centuries. APOGEE's three-dimensional map will provide key information for resolving central questions about how our galaxy formed over the many billions of years of its history.

APOGEE's spectra of stars will help unlock the history of our galaxy, and the key is learning the compositions and motions of stars in each region. Because elements heavier than hydrogen and helium were produced in stars and spread through the Galaxy by stellar explosions and stellar winds, astronomers know that stars with more of these heavy elements must have formed more recently, after previous generations of stars had time to create those heavy elements.

APOGEE data also provide a rich context for investigating a wide range of questions about the stars themselves. Because APOGEE observes each target star several times, it can identify changes in each star's spectrum over time. Mahadevan has led efforts to characterize low-mass stars and binary stars found during the APOGEE experiment.

The SDSS-III Data Release 10 also is publishing another 685,000 spectra from the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). These new spectra come from galaxies and quasars whose light began traveling toward Earth when our universe was much younger, just as the mysterious force of "dark energy" was beginning to influence the universe's expansion. "The BOSS project continues to produce superb data that allow numerous investigations ranging from the large scale evolutionary history of the universe to the properties of supermassive black holes, which have the size of the solar system," said Distinguished Professor of Astronomy and Astrophysics Niel Brandt, another Penn State scientist involved with SDSS-III.

SDSS-III, a six-year survey of nearby stars, the Milky Way galaxy, and the distant cosmos, will complete its observations in 2014. The Sloan Foundation 2.5-meter telescope at the Apache Point Observatory in New Mexico conducts observations every night that feed either the BOSS optical or the APOGEE infrared spectrographs. Donald Schneider, Distinguished Professor of Astronomy and Astrophysics at Penn State, is the Survey Coordinator and Scientific Publication Coordinator for SDSS-III.

"We've been producing public data releases since 2001," said SDSS-III Spokesperson Michael Wood-Vasey of the University of Pittsburgh. "Public access to data always has been a key goal of our project, and we're proud to continue that tradition today with this new release, which is rich with information about our own galaxy." All of these data are available online to researchers and the public.

CONTACTS

Suvrath Mahadevan, suvrath@astro.psu.edu, 814-865-0261

Niel Brandt, nbrandt@astro.psu.edu, 814-865-3509

Donald Schneider, dps7@psu.edu, 814-863-9554

Barbara Kennedy (PIO): 814-863-4682, science@psu.edu

MORE INFORMATION ABOUT SDSS-III

The full SDSS-III press release is online at http://www.sdss3.org/press/dr10.php.

Funding for SDSS-III has been provided by the Alfred P. Sloan Foundation, the Participating Institutions, the National Science Foundation, and the U.S. Department of Energy Office of Science. The SDSS-III web site is http://www.sdss3.org.

SDSS-III is managed by the Astrophysical Research Consortium for the Participating Institutions of the SDSS-III Collaboration including the University of Arizona, the Brazilian Participation Group, Brookhaven National Laboratory, Carnegie Mellon University, University of Florida, the French Participation Group, the German Participation Group, Harvard University, the Instituto de Astrofisica de Canarias, the Michigan State/Notre Dame/JINA Participation Group, Johns Hopkins University, Lawrence Berkeley National Laboratory, Max Planck Institute for Astrophysics, Max Planck Institute for Extraterrestrial Physics, New Mexico State University, New York University, Ohio State University, Pennsylvania State University, University of Portsmouth, Princeton University, the Spanish Participation Group, University of Tokyo, University of Utah, Vanderbilt University, University of Virginia, University of Washington, and Yale University.