Large galaxies like our own Milky Way often
collide with neighbouring galaxies. Most of the time the collision is with a smaller
"dwarf" galaxy, resulting in the smaller galaxy being eaten or cannibalized by
the larger galaxy. However, once in awhile, a large galaxy may encounter another large
galaxy. The result may be the merger of these galaxies, forming a single elliptical
galaxy.
Galaxy collisions take much longer than collisions we are used to. A merger of two large
galaxies may take as long as 1 billion years to occur! As a result, we are unable to sit
back and watch a collision happen. The best we can do is to take a snapshot of a
collision-in-progress. A number of these snapshots have been compiled below. Some involve
galaxies which are relatively nearby. Here at UVic, some of us are involved in a detailed
study of distant galaxies. We have identified some galaxy collisions taking place in
distant parts of the universe. One way to see what collisions might look like is to
generate a computer simulation. To see some neat movies of these collisions, click on the
icon below.
Click to enlarge.
This Hubble Space Telescope
image provides a detailed look at a brilliant "fireworks show" at the center of
a collision between two galaxies. Hubble has uncovered over 1,000 bright, young star
clusters bursting to life as a result of the head-on wreck.
LEFT
SIDE
A
ground-based telescopic view of the Antennae galaxies (known formally as NGC 4038/4039) -
so named because a pair of long tails of luminous matter, formed by the gravitational
tidal forces of their encounter, resembles an insect's antennae. The galaxies are located
63 million light-years away in the southern constellation Corvus.
RIGHT
SIDE
The
respective cores of the twin galaxies are the orange blobs, left and right of image
center, crisscrossed by filaments of dark dust. A wide band of chaotic dust, called the
overlap region, stretches between the cores of the two galaxies. The sweeping spiral- like
patterns, traced by bright blue star clusters, shows the result of a firestorm of star
birth activity which was triggered by the collision.
This
natural-color image is a composite of four separately filtered images taken with the Wide
Field Planetary Camera 2 (WFPC2), on January 20, 1996. Resolution is 15 light-years per
pixel (picture element).
Question:
What
exactly happens when two galaxies collide?
Answer:
Collisions
of galaxies are tremendous things (a galaxy is a LOT bigger than anything on Earth that
you can imagine colliding!) and generate a lot of energy, heating and mixing up the gases
in the two galaxies, making a good place for star formation. Unlike car collisions,
galaxies collisions take a very long time - as many as a billion years or more for large
galaxies!
Galaxy
collisions are complex interactions and there are many people trying to figure out how
galaxies interact when they get close enough together, and how they affect each other. One
of the ways scientists do this is by studying numerical simulations of colliding galaxies.
The simulations capture much of the important physics but can be run on a much faster
timescale.
Click to enlarge. |
COLLIDING GALAXIES
