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Unmanned Spaceflight.com _ Chit Chat _ Andromeda's Satellite Galaxies

Posted by: Canopus Jan 24 2006, 01:17 PM

QUOTE

An unusually high number of galaxies are aligned along a single plane running through the center of the giant Andromeda galaxy. Scientists don’t have a theory to explain why.

Galactic cannibalism or dark matter may be responsible...

QUOTE

Using the Hubble Space Telescope, Eva Grebel and Andrew Koch from the University of Basel in Switzerland found that nine out of Andromeda’s fourteen dwarf galaxy satellites reside in a single plane. The plane is about 52,000 light-years wide and is aligned perpendicular to Andromeda’s own galactic plane, within which the galaxy’s stars orbit about the center...

The Milky Way was found to contain two similar planes of satellite galaxies in the late 1980s, but with nothing to compare them to, astronomers couldn’t tell if such planes were a general property of galaxy formation or whether they were just a statistical fluke.

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Perhaps long ago Andromeda swallowed a nearby orbiting galaxy but did a messy job of it; the galactic crumbs from that meal became Andromeda’s satellite dwarf galaxies. Such instances of galactic cannibalism are common and are believed to play a major role in galaxy formation...

Another intriguing possibility is that the satellite galaxies are actually embedded in a stream of hypothetical dark matter flowing between two massive objects.

Posted by: ljk4-1 Jan 24 2006, 02:04 PM

Science/Astronomy:

* Strange Setup: Andromeda's Satellite Galaxies All Lined Up

http://www.space.com/scienceastronomy/060123_andromeda_plane.html

An unusually high number of galaxies are aligned along a single plane running
through the center of the giant Andromeda galaxy. Scientists don't have a theory
to explain why.

Posted by: ljk4-1 Jan 31 2006, 09:30 PM

Paper: astro-ph/0601599

Date: Thu, 26 Jan 2006 14:33:59 GMT (519kb)

Title: Andromeda X, A New Dwarf Spheroidal Satellite of M31: Photometry

Authors: Daniel B. Zucker, Alexei Y. Kniazev, David Martinez-Delgado, Eric F.
Bell, Hans-Walter Rix, Eva K. Grebel, Jon A. Holtzman, Rene A. M. Walterbos,
Constance M. Rockosi, Donald G. York, J. C. Barentine, Howard Brewington, J.
Brinkmann, Michael Harvanek, S. J. Kleinman, Jurek Krzesinski, Dan Long, Eric
H. Neilsen, Jr., Atsuko Nitta, Stephanie A. Snedden

Comments: 4 pages, 4 figures; submitted to Astrophysical Journal Letters

\\
We report the discovery of Andromeda X, a new dwarf spheroidal satellite of
M31, based on stellar photometry from the Sloan Digital Sky Survey (SDSS).
Using follow-up imaging data we have estimated its distance and other physical
properties. We find that Andromeda X has a dereddened central surface
brightness of mu_V,0 ~ 26.7 mag arcsec^-2 and a total apparent magnitude of
V_tot ~ 16.1, which at the derived distance modulus, (m - M)_0 ~ 24.12 - 24.34,
yields an absolute magnitude of M_V ~ -8.1 +/- 0.5; these values are quite
comparable to those of Andromeda IX, a previously-discovered low luminosity M31
satellite. The discoveries of Andromeda IX and Andromeda X suggest that such
extremely faint satellites may be plentiful in the Local Group.

\\ ( http://arXiv.org/abs/astro-ph/0601599 , 519kb)

Posted by: ljk4-1 Feb 22 2006, 04:17 PM

Milky Way vs. Andromeda: Study Settles Which Is More Massive

http://www.space.com/scienceastronomy/060221_stues_dark_matter.html

Astronomers have figured out the density of dark matter and how fast it's moving
in our corner of the universe. The research brings scientists one step closer to
figuring out what the elusive stuff is and also settles once and for all the
question of which galaxy—our Milky Way or Andromeda—is more massive.