Rensselaer Magazine, March 2002: At Rensselaer

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Astrophysics

Image of spiral galaxy NGC 4414
Hubble Heritage Team (AURA/STScI/NASA)

Peering Deeper Into the Milky Way

Heidi Jo Newberg ’87, associate professor of physics, applied physics and astronomy, and a team of researchers have identified new star structures in the halo of the Milky Way that could alter the standard model of the galaxy and provide a better insight into how the Milky Way was formed.

Newberg and Brian Yanny, an astrophysicist at the Fermilab (the Fermi National Accelerator Laboratory administered by the U.S. Department of Energy’s Office of Science) are the principal authors of a paper on the subject to be published by The Astrophysical Journal.

The research may be a first step in the development of complete galactic models for the halo. The star streams were identified from positions, colors, and brightness of five million stars detected in the Sloan Digital Sky Survey (SDSS), an international scientific collaboration that is cataloging the heavens to an unprecedented depth, area, and accuracy.

Newberg and Yanny say the results yielded by the SDSS database provide a “deeper, more global picture of the Milky Way’s stellar system.”

An unexpectedly large number of blue stars have been found within 20 degrees of the galactic plane, say Newberg and Yanny. These stars could be part of a disrupted dwarf galaxy, or a disk-like distribution of stars that is puffier than accepted models of stellar disks in the galaxy and flatter than the spherical distribution in the halo.

Newberg says the findings have an impact on several active fields of astronomical research, including galactic structure, evolution of the Milky Way, the distribution of mass in the galaxy, and galaxy formation in the early universe.

“Although we originally set out to measure properties of a smooth halo, we now find it difficult to determine which, if any, of the structures of the halo belong to that population,” says Newberg.

“Stars in the halo appear to be grouped into distinct streams in the sky,” says Yanny. “A careful look at the stellar properties shows that they come from yet unidentified parent populations, perhaps other dwarf galaxies that have long since been torn apart.”

Rensselaer Magazine: March 2002
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