Astronomers at The
University of Texas at Austin believe they have discovered the answer to a 20-year debate over how the mysterious cosmic “
dark matter”
is distributed in small galaxies. They found that the distribution, on
average, follows a simple law of decreasing density from the galaxy’s
center, although the exact distribution often varies from galaxy to
galaxy. The findings are published today in
The Astrophysical Journal Letters.
Dark
matter is matter that gives off no light, but that astronomers detect
by seeing its gravitational tug on other objects (like stars). Theories
abound on what dark matter might be made of — unseen particles, dead
stars, and more — but nobody knows for sure. Though mysterious,
understanding the nature of dark matter is important, because it makes
up most of the matter in the universe. The only way to understand how
the cosmos evolved to its present state is to decode dark matter’s role.
For
that reason, astronomers study the distribution of dark matter within
galaxies and on even larger scales. Dwarf galaxies, in particular, make
great laboratories to study dark matter, say astronomers John Jardel and
Karl Gebhardt,
because they contain up to 1,000 times more dark matter than normal
matter. Normal galaxies like the Milky Way, on the other hand, contain
only 10 times more dark matter than normal matter.
Read More Here
****************************************************
Multiple streams of Sagittarius dwarf galaxy
segasai
Uploaded on Nov 26, 2011
The
illustration of multiple streams produced by the disruption of the
Sagittarius dwarf galaxy in the Milky Way halo. The orange sphere shows
the location of the Sun in the Galaxy. The Sagittarius dwarf galaxy
itself is located in the middle of the stream.The size of the area shown
in the movie is approximately 600 thousands light years (200
kiloparsecs)
