|
|
Images:
The following images are based on Figure 1 of our review for
Annual Reviews on Astronomy and Astrophysics on Galactic Bulges (Wyse,
Gilmore & Franx, 1997, ARAA, 35, 637) and show an optical image of
the central regions of the Milky Way Galaxy, adapted (by Richard Sword, IoA,
Cambridge) from that of Madsen & Laustsen (1986). The field
covered is 70 deg by 50 deg. The Galactic Plane is illustrated
by the horizontal line, and the Galactic
Center by the cross in
the center of the image. The smooth solid curves on either side of
the Plane indicate the outline of the COBE/DIRBE image of the
central Galaxy. The approximate known outline of the
Sagittarius dwarf spheroidal galaxy is the extended irregular
shape below the Galactic
Center (taken
from Ibata, Wyse et al 1997). This companion galaxy to the Milky
Way is actually on the far side of the Galactic Center.
This little
galaxy cannot be noticed on images of the central regions of the
Milky Way, due to its extremely low surface brightness; there are
too few stars that are members of this galaxy, compared to the many
stars along the line-of sight that are in the Milky Way Galaxy.
This little galaxy was discovered in 1994 by Ibata , Gilmore and
Irwin, during a study of stars in the central regions of our own
Galaxy, the Milky Way. These astronomers studied stars in the
little boxes that run parallel and perpendicular to the Galactic
PLane in this image. They found that some of the stars in the
lines-of-sight that run through the outline of the Sagittarius
dwarf on the image were not moving as they should if they were in the
central regions of the Milky Way. They realised they had
found a little galaxy, hiding.
|
![Sagittarius dwarf [gif]](araa97_fig1.gif){kind=link}