Milky Way's Formation Theory Questioned

Author: * Sokni Hvitaskald - 26 Posts on this thread out of 1,073 Posts sitewide.
Date: Sep 18, 2006 - 21:24

By Jeanna Bryner
Staff Writer
posted: 18 September 2006
06:09 am ET

The Milky Way might not have formed through the merger of several smaller galaxies as previously thought, but by some other unknown process, a new study suggests.

Home to our solar system and viewable in our own backyards, this crowd of stars called the Milky Way offers astronomers one of the best chances for understanding how a galaxy forms.

“The Milky Way is the only galaxy in the universe that we can study in detail. Still, we haven't yet understood how it did form," Manuela Zoccali of the Department of Astronomy and Astrophysics at the Pontifical Catholic University of Chile told SPACE.com. "Shedding light on its formation is fundamental to understand how all the galaxies in the universe have formed."

Parts of our galaxy

The Milky Way, often seen from Earth as a hazy halo of stars in the night sky, is a spiral galaxy with several arms of gas, dust and stars, coiling out from a spherical nucleus in the shape of a flattened disk. The starry center is called a bulge because it protrudes from the flattened disk.

Until now, the best theoretical models predicted dwarf galaxies beget larger and larger galaxies, as multiple star packs clumped together or a heftier galaxy started gobbling up its neighbors. If this were the case for the Milky Way, Zoccali said, the stars in the galactic bulge should have once been part of the disk. Over eons, as more galactic mergers occurred, some of the stars should be tugged toward the center to form the bulge.

“We have proved that this is not the case,” Zoccali said. Using the European Southern Observatory’s Very Large Telescope (VLT) array in Paranal, Chile, an international team of astronomers, led by Zoccali, examined the chemical makeup of 50 giant stars in the direction of the galactic bulge. They discovered the stars at the center of the Milky Way showed distinct element amounts compared to the disk stars, a sign that the two galaxy components formed separately.

Read the rest at:
http://www.space.com/scienceastronomy/060918_galactic_bulge.html