This false-color infrared image from NASA's Spitzer Space Telescope shows
little "dwarf galaxies" forming in the "tails" of two larger galaxies that
are colliding together. The big galaxies are at the center of the picture,
while the dwarfs can be seen as red dots in the red streamers, or tidal
tails. The two blue dots above the big galaxies are stars in the
foreground.
Galaxy mergers are common occurrences in the universe; for example, our
own Milky Way galaxy will eventually smash into the nearby Andromeda
galaxy. When two galaxies meet, they tend to rip each other apart, leaving
a trail, called a tidal tail, of gas and dust in their wake. It is out of
this galactic debris that new dwarf galaxies are born.
The new Spitzer picture demonstrates that these particular dwarfs are
actively forming stars. The red color indicates the presence of dust
produced in star-forming regions, including organic molecules called
polycyclic aromatic hydrocarbons. These carbon-containing molecules are
also found on Earth, in car exhaust and on burnt toast, among other
places. Here, the molecules are being heated up by the young stars, and,
as a result, shine in infrared light.
This image was taken by the infrared array camera on Spitzer. It is a
4-color composite of infrared light, showing emissions from wavelengths
of 3.6 microns (blue), 4.5 microns (green), 5.8 microns (orange), and 8.0
microns (red). Starlight has been subtracted from the orange and red
channels in order to enhance the dust features.
