NASA’s Spitzer Space Telescope has set its infrared sight on a major
galactic collision and witnessed not death, but a teeming nest of
life.

The colliding galaxies, called the Antennae galaxies, are in the
process of merging together. As they churn into each other, they throw
off massive streamers of stars and dark clouds of dust. Spitzer’s
heat-seeking eyes peered through that dust and found a hidden
population of newborn stars.

The new Spitzer image, available at
http://www.spitzer.caltech.edu/Media/releases/ssc2004-14/visuals.shtml ,
is reported in one of 86 Spitzer papers published in the September
issue of The Astrophysical Journal Supplement. This special
all-Spitzer issue comes just after the one-year anniversary of the
observatory’s launch, and testifies to its tremendously successful
first year in space.

“This abundance of Spitzer papers just one year after launch shows
that the telescope is truly providing a new window on the universe,”
said Dr. Michael Werner, project scientist for Spitzer at NASA’s Jet
Propulsion Laboratory, Pasadena, Calif. “These papers report the
earliest results, so the best is yet to come.”

In the latest Antennae galaxies study, Spitzer uncovered a new
generation of stars at the site where the two galaxies clash.

“We theorized that there were stars forming at that site, but we
weren’t sure to what degree,” said Dr. Zhong Wang, lead author of the
new paper and an astronomer at the Harvard-Smithsonian Center for
Astrophysics, Cambridge, Mass. “Now we see that the majority of
star-forming activity in both galaxies occurs in the overlap regions
where the two meet.”

The Antennae galaxies are a classic example of a galactic merger in
action. These two spiral galaxies, located 68 million light-years away
from Earth, began falling into each other around a common center of
gravity about 800 million years ago. As they continue to crash
together, clouds of gas are shocked and compressed in a process
thought to trigger the birth of new stars. Astronomers believe that
the two galaxies will ultimately merge into one spheroidal-shaped
galaxy, leaving only hints of their varied pasts.

Galactic mergers are common throughout the universe and play a key
role in determining how galaxies grow and evolve. Our own Milky Way
galaxy, for example, will eventually collide with our closest
neighbor, the Andromeda galaxy.

Previous images of the Antennae taken by visible-light telescopes show
striking views of the swirling duo, with bright pockets of young stars
dotting the spiral arms. At the center of the galaxies, however, where
the two overlap, only a dark cloud of dust can be seen. In the new
false-color Spitzer image, which has been combined with an image from
a ground-based, visible-light telescope to highlight new features,
this cloud of buried stars appears bright red. The visible-light
information, on the other hand, is colored blue and indicates regions
containing older stars. The nuclei, or centers, of the two galaxies
are white.

“This more complete picture of star-formation in the Antennae will
help us better understand the evolution of colliding galaxies, and the
eventual fate of our own,” said Dr. Giovanni Fazio, a co-author of the
research and an astronomer at the Harvard-Smithsonian Center for
Astrophysics.” Fazio is principal investigator for the infrared array
camera on Spitzer, which captured the new Antennae image.

JPL manages the Spitzer Space Telescope mission for NASA’s Science
Mission Directorate, Washington. Science operations are conducted at
the Spitzer Science Center at the California Institute of Technology
in Pasadena. JPL is a division of Caltech. Spitzer’s infrared array
camera was built by NASA Goddard Space Flight Center, Greenbelt, Md.

Information about Spitzer can be found at
http://www.spitzer.caltech.edu/ .