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Mapping the History of Our Galaxy

Physics, Applied Physics, and Astronomy

Mapping the History of Our Galaxy

Rensselaer’s Heidi Jo Newberg has spent the past eight years immersed in the Milky Way, sifting through images of a hundred million stars, tracking the motions of 240,000 of them, and helping to map the history of the galaxy. Her discoveries have enhanced our understanding of the Milky Way, raised additional questions about dark matter—and sent Newberg in search of an even larger spectroscopic survey.

An associate professor of physics, applied physics, and astronomy, Newberg initiated the Sloan Extension for Galactic Understanding and Exploration (SEGUE), one of three projects included in the Sloan Digital Sky Survey II (SDSS-II).

SDSS is one of the most ambitious astronomical surveys ever undertaken. Over eight years, it measured the brightness and positions of hundreds of millions of galaxies, stars, and quasars. Data was released to scientists annually, with the final release on Oct. 31, 2008.

SDSS-III is now under way and its SEGUE-II will build on the research conducted by Newberg and her collaborators from 18 institutions worldwide. Newberg also is hoping to probe even deeper by partnering with the scientists who will survey the stars of the Milky Way using China’s Large Sky Area Multi-Object Fiber Spectroscopic Telescope (LAMOST), which is nearing completion.

“Most of the mass in the Milky Way is dark matter,” Newberg explains. “The only way we can probe that is to look more closely at the stars. If we can determine their velocity, we can see which direction they’re moving in, and can understand how dark matter is distributed in our galaxy.”

SDSS is one of the most ambitious astronomical surveys ever undertaken. Over eight years, it measured the brightness and positions of hundreds of millions of galaxies, stars, and quasars.
Since SDSS gathered so much data, a great deal has yet to be analyzed. Eventually, data from SDSS and subsequent surveys will produce the first three-dimensional map of the Milky Way and the motions of the stars.

Some of the data also has pointed researchers, including Newberg, in new directions. When SDSS began, scientists thought that the stars in the outer parts of the Milky Way formed one component of the galaxy with a smoothly varying density. Instead, Newberg and her colleagues found that there were enormous lumps of stars, as far across as the distance between the sun and the center of the Milky Way, and some which stretched 360 degrees around the sky. The lumpy outer parts of the galaxy are proof that some, or maybe all, of the Milky Way was formed from the merging of smaller “dwarf” galaxies together to make one large, spiral galaxy.

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Rensselaer (ISSN 0898-1442) is published in Spring, Summer, Fall, and Winter by the Office of Strategic Communications and External Relations, Rensselaer Polytechnic Institute, Troy, NY 12180-3590. Opinions expressed in these pages do not necessarily reflect the views of the editors or the policies of the Institute. ©2009 Rensselaer Polytechnic Institute.