Galaxies Don Mask of Stars in New Spitzer Image
A pair of dancing galaxies appears dressed for a cosmic masquerade
in a new image from NASA's Spitzer Space Telescope.
The infrared picture shows what looks like two icy blue eyes staring
through an elaborate, swirling red mask. These "eyes" are actually
the cores of two merging galaxies, called NGC 2207 and IC 2163,
which recently met and began to twirl around each other.
Image right: In this new false-colored image from NASA's Spitzer Space Telescope, the mysterious blue eyes are actually starlight from the cores of two merging galaxies, called NGC 2207 and IC 2163. The mask is the galaxies' dusty spiral arms. Image credit: NASA/JPL-Caltech/Vassar
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The "mask" is made up of the galaxies' twisted spiral arms. Dotted
along the arms, like strings of decorative pearls, are dusty clusters
of newborn stars. This is the first time that clusters of this type,
called "beads on a string" by astronomers, have been seen in NGC 2207
and IC 2163.
"This is the most elaborate case of beading we've seen in galaxies,"
said Dr. Debra Elmegreen of Vassar College in Poughkeepsie, N.Y. "They
are evenly spaced and sized along the arms of both galaxies."
Elmegreen is lead author of a paper describing the Spitzer observations
in the May 1 issue of the Astrophysical Journal. The image can be viewed
Astronomers say the beads were formed when the galactic duo first met.
"The galaxies shook each other, causing gas and dust to move around and
collect into pockets dense enough to collapse gravitationally," said Dr.
Kartik Sheth of NASA's Spitzer Science Center at the California Institute
of Technology in Pasadena. Once this material condensed into thick
bead-like clouds, stars of various sizes began to pop up within them.
Spitzer's infrared camera was able to see the dusty clouds for the first
time because they glow with infrared light. The hot, young stars housed
inside the clouds heat up the dust, which then radiates at infrared wavelengths.
This dust is false-colored red in the image, while stars are represented in blue.
The Spitzer data also reveal an unusually bright bead adorning the left side
of the "mask." This dazzling orb is so packed full of dusty materials that it
accounts for five percent of the total infrared light coming from both galaxies.
Elmegreen's team thinks the central stars in this dense cluster might have merged
to become a black hole.
Visible-light images of the galaxies show stars located inside the beads, but the
beads themselves are invisible. In those pictures, the galaxies look more like a
set of owl-like eyes with "feathers" of scattered stars.
NGC 2207 and IC 2163 are located 140 million light-years away in the Canis Major
constellation. The two galaxies will meld into one in about 500 million years,
bringing their masquerade days to an end.
Other authors of this research include Bruce Elmegreen of IBM Watson Research Center,
Yorktown Heights, N.Y., Michele Kaufman of Ohio State University, Columbus; Curt Struck
of Iowa State, Ames; Magnus Thomasson of Onsala Space Observatory, Sweden; and Elias
Brinks of the University of Hertfordshire, United Kingdom.
The Jet Propulsion Laboratory manages the Spitzer Space Telescope mission for NASA's
Science Mission Directorate, Washington. Science operations are conducted at the Spitzer
Science Center at Caltech. JPL is a division of Caltech. Spitzer's infrared array camera
was built by NASA's Goddard Space Flight Center, Greenbelt, Md. The instrument's principal
investigator is Dr. Giovanni Fazio of the Harvard-Smithsonian Center for Astrophysics.
For more information about Spitzer, visit http://www.spitzer.caltech.edu/spitzer
For more information about NASA and agency programs on the Web, visit http://www.nasa.gov/home/
Jet Propulsion Laboratory, Pasadena, Calif.