This false-color image composite from NASA's Spitzer Space Telescope
reveals hidden populations of newborn stars at the heart of the colliding
"Antennae" galaxies. These two galaxies, known individually as NGC 4038
and 4039, are located around 68 million light-years away and have been
merging together for about the last 800 million years. The latest Spitzer
observations provide a snapshot of the tremendous burst of star formation
triggered in the process of this collision, particularly at the site
where the two galaxies overlap.
The image is a composite of infrared data from Spitzer and visible-light
data from Kitt Peak National Observatory, Tucson, Ariz. Visible light
from stars in the galaxies (blue and green) is shown together with
infrared light from warm dust clouds heated by newborn stars (red).
The two nuclei, or centers, of the merging galaxies show up as
yellow-white areas, one above the other. The brightest clouds of forming
stars lie in the overlap region between and left of the nuclei.
Throughout the sky, astronomers have identified many of these so-called
"interacting" galaxies, whose spiral discs have been stretched and
distorted by their mutual gravity as they pass close to one another.
The distances involved are so large that the interactions evolve on
timescales comparable to geologic changes on Earth. Observations of such
galaxies, combined with computer models of these collisions, show that
the galaxies often become forever bound to one another, eventually
merging into a single, spheroidal-shaped galaxy.
Wavelengths of 0.44 microns are represented in blue, .70 microns in green
and 8.0 microns in red. This image was taken on Dec. 24, 2003.