Colliding Galaxies (3) ...
The adjacent image shows one of the longest galaxies known, the SBb barred spiral
NGC 6872, as imaged by the
European Southern Observatory.
This galaxy measures 750,000
light years in length (about 8 times longer than the Milky Way's diameter).
It is thought that the shape has something to do with the interaction of NGC 6872 and
the S0
galaxy
IC 4970, which is just above the center of the picture (the bright object to the lower
right of the spiral's center is a foreground star in our galaxy).
The upper left spiral arm of NGC 6872 shows an unusual amount
of star formation, which accounts for its blue color.
It is thought that this star formation
is associated with the recent passage of IC 4970 through this region of NGC 6872.
NGC 6872 is about 300 million light years away, in
the southern sky constellation
Pavo (the Peacock).
Example: Stephan's Quintet
An interesting example of possible galactic collisions
can be seen in
Stephan's Quintet,
shown in the adjacent figure.
This is a close grouping of five galaxies
(the cores of the galaxies are the brightest spots; one galaxy is
only partially visible in the lower right part of the image).
Four of these galaxies are
probably physically close because they have similar
redshifts;
the fifth--in the lower left--is probably
accidentally in the line of
sight since it has a very different redshift.
The three galaxies in the upper part of the image
appear to be colliding with each
other.
