Disorder in Stephan's Quintet
Credit:
W. C. Keel and R. E. White III
(U. Alabama, Tuscaloosa),
Kitt Peak 2.1-meter Telescope
What are five closely grouped galaxies doing in this image?
The grouping is commonly known as Stephan's
Quintet. Four of the galaxies show essentially the same redshift
suggesting that they are at the same distance from us. The large
bluish spiral below and left of
center actually has a smaller redshift
than the others, indicating it is much closer. It is probably
a foreground object which happens to lie along the line of sight
to the more distant galaxies. Of the four distant galaxies,
three seem to be colliding, showing
serious distortions due to gravitational tidal forces. The fourth
is a normal appearing elliptical galaxy
(at the lower right edge of the field). Recent results suggest
that collisions play an important role in the life cycles of galaxies.