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Milky Way Formation Theory Questioned

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posted on Sep, 18 2006 @ 06:30 PM
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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.

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.
“In other words, bulge stars did not originate in the disk and then
migrate inward to build up the bulge but rather formed independently of
the disk,” Zoccali said.


SOURCE:
Space.com


Ok, so not as interesting to other people as it is to me, but it's still cool.

This is what science is all about to me.


Comments, Opinions?




posted on Sep, 18 2006 @ 06:44 PM
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Well...that is interesting, because it totally destroys what I always considered to be the case. In my poorly structured universe, I considered a large black hole to be at the center of our universe, which pulled the stars into the middle.

Stranger and stranger still.

[edit on 18-9-2006 by masqua]



posted on Sep, 18 2006 @ 07:20 PM
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All well and good, but looking at the chemical makeup of 50 giant stars isn't enough to figure this one out. It can be easily said that the standard model of galaxy formation can acount for the chemical differences. The Galaxy didn't just start off gobbling up smaller entities that were passing by or orbiting it. The main body of the Galaxy formed from the collapse of a vast cloud of gas, and as is want of collapsing gas clouds, the central regions become the most concentrated. Forming a bulge like structure. The stars that became part of the central bulge of the Galaxy were forming in this area as the Galaxy was collapsing. The smaller objects which had already formed around the Galaxy became incorporated into the Galaxy as its gravity began to pull them in, but not all of them became parts of the main body. Some still stayed in orbit..... as the globular clusters and the other satellite galaxies which weren't incorporated. The outer regions which stayed in orbit around the Galaxy became part of the galactic halo, which apart from globular clusters and satellite galaxies, is also home to many billions of individual stars and other objects..

The disk of the Galaxy formed as the cloud of gas collapsed, but a little bit later than the bulge. Since the original gas cloud was spinning before it collapsed, as it collapsed part of it formed a disk of material around the central bulge due to the transfer of angular momentum from the central regions to the disk, as well as centrifugal forces acting on the spinning gas. It became flattened and disk like. Those stars which formed in the bulge are older than the disk stars, they generally contain less metals (elements other than hydrogen and helium) to varying degrees, and some of the chemicals difference can be explained by differences in concentrations of metals due to diffusion processes as the Galaxy collapsed. Also by later capture of smaller galaxies that formed separately from the Galaxy and had a chance to evolve somewhat before being ripped apart by the Galaxy.

Even now, the Galaxy is tearing apart several smaller unfortunate objects...... the Sagittarius Dwarf, the Ursa Major Dwarf and what is now an amorphous stream of stars in Virgo called the "Field of Streams". In the future it will most likely rip apart the Magellanic Clouds and then in about 3 billion years, the Galaxy itself will begin to collide with the Andromeda Galaxy. What will be left will be a supermassive elliptical galaxy of about 4-6 trillion solar masses, a bit more than half of which will be contributed by our Galaxy. Though whilst smaller than the Andromeda Galaxy in linear size, is in actual fact the most massive of the two big spirals in the Local Group of Galaxies.


[edit on 18-9-2006 by GhostITM]



posted on Sep, 18 2006 @ 07:29 PM
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Originally posted by masqua
Well...that is interesting, because it totally destroys what I always considered to be the case. In my poorly structured universe, I considered a large black hole to be at the center of our universe, which pulled the stars into the middle.

Stranger and stranger still.

[edit on 18-9-2006 by masqua]


That black hole, masqua, formed whilst the initial collapse of the Galaxy occured. What happened is that an enormous concentration of mass in the centre of the collapse reached its mass limit and then collapsed passed the Schwarzchild Radius for an object of its size, which for our Galaxy was an object around 2-3 million solar masses and about the size of the orbit of Mercury. It may have also swallowed smaller black holes that formed near it during the collapse, as well. Plus gas and some newborn stars.


[edit on 18-9-2006 by GhostITM]



posted on Sep, 18 2006 @ 07:29 PM
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That was very informative, and honestly a very good post.

If I had any WATS awards left, you'd most certainly get one.



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