Chandra Observes Dark Matter for the First Time!

" Menlo Park, CA-Dark matter, the elusive stuff that makes up a
quarter of the universe, has been seen in isolation for the first time.
Marusa Bradac of the Kavli Institute for Particle Astrophysics and
Cosmology (KIPAC), located at the Department of Energy's Stanford
Linear Accelerator Center (SLAC), and her colleagues made the landmark
observations by studying a galaxy cluster 3 billion light years away.

"We had predicted the existence of dark matter for decades, but now
we've seen it in action," said Bradac. "This is groundbreaking." "

See the pictures and the rest of the story at the site:

http://home.slac.stanford.edu/pressr...6/20060821.htm

Dark matter is thought to make up 5 times more mass than luminous
matter in the universe.

Double-A

Double-A wrote:
" Menlo Park, CA-Dark matter, the elusive stuff that makes up a
quarter of the universe, has been seen in isolation for the first time.
Marusa Bradac of the Kavli Institute for Particle Astrophysics and
Cosmology (KIPAC), located at the Department of Energy's Stanford
Linear Accelerator Center (SLAC), and her colleagues made the landmark
observations by studying a galaxy cluster 3 billion light years away.

"We had predicted the existence of dark matter for decades, but now
we've seen it in action," said Bradac. "This is groundbreaking." "

See the pictures and the rest of the story at the site:

http://home.slac.stanford.edu/pressr...6/20060821.htm

Dark matter is thought to make up 5 times more mass than luminous
matter in the universe.

Double-A



This "observation" appears to contradict the theory that predicted it!

Question: If dark matter is "required" to explain how a galaxy holds
together and dark matter reacts with "normal" matter only through
gravity how is it that any galaxy has dark matter associated with it?

By this I mean that if during a galactic collision the 2 forms of matter
are separated as implied by the above, what "slows" the dark matter down
enough so that it could again be integral with the originating galaxy
and not remain separate where the 2 forms of matter would obit a mutual
mass center. Gravity waves alone would take far to long for the systems
to become stable.
Think of a small galactic cluster colliding with a large galaxy, the
"normal" matter would be "captured" through the medium of "drag", while
the dark matter would continue on. After several collisions the balance
of dark to normal matter would be altered in a host galaxy while
external to it there would be many "ghost" galaxy's of dark matter.
These external "ghost" galaxy's would not be able to affect the orbital
speeds of the fringe stars. Theory implies that only mass "inside" an
orbit has any affect on orbital speed, and (I believe)it was the
discrepancy of orbital speeds predicted to observed speeds in galaxy's
as the origin of the dark matter theory. So why don't these galaxy's
fly apart? It also appears that galactic collisions are not at all
uncommon.

Just a little puzzled by all of this.