Side-by-Side Comparison
Click on image for larger view
The outlying regions around the Southern Pinwheel galaxy, or M83, are
highlighted in this composite image from NASA's Galaxy Evolution Explorer
and the National Science Foundation's Very Large Array in New Mexico. The
blue and pink pinwheel in the center is the galaxy's main stellar disk,
while the flapping, ribbon-like structures are its extended arms.
The Galaxy Evolution Explorer is an ultraviolet survey telescope. Its
observations, shown here in blue and green, highlight the galaxy's
farthest-flung clusters of young stars up to 140,000 light-years from its
center. The Very Large Array observations show the radio emission in red.
They highlight gaseous hydrogen atoms, or raw ingredients for stars, which
make up the lengthy, extended arms.
Astronomers are excited that the clusters of baby stars match up with the
extended arms, because this helps them better understand how stars can be
created out in the "backwoods" of a galaxy.
In this image, far-ultraviolet light is blue, near-ultraviolet light is
green and radio emission at a wavelength of 21 centimeters is red.
What Lies Beyond the Edge of a Galaxy
The side-by-side comparison shows the Southern Pinwheel galaxy, or M83, as
seen in ultraviolet light (right) and at both ultraviolet and radio
wavelengths (left). While the radio data highlight the galaxy's long,
octopus-like arms stretching far beyond its main spiral disk (red), the
ultraviolet data reveal clusters of baby stars (blue) within the extended
arms.
The ultraviolet image was taken by NASA's Galaxy Evolution Explorer
between March 15 and May 20, 2007, at scheduled intervals. Back in 2005,
the telescope first photographed M83 over a shorter period of time. That
picture was the first to reveal far-flung baby stars forming up to 63,000
light-years from the edge of the main spiral disk. This came as a surprise
to astronomers because a galaxy's outer territory typically lacks high
densities of star-forming materials.
The newest picture of M83 from the Galaxy Evolution Explorer is shown at
the right, and was taken over a longer period of time. In fact, it is one
of the "deepest," or longest-exposure, images of a nearby galaxy in
ultraviolet light. This deeper view shows more clusters of stars, as well
as stars in the very remote reaches of the galaxy, up to 140,000
light-years away from its core.
The view at the left is a combination of the ultraviolet picture at the
right and data taken by the telescopes of the National Science
Foundation's Very Large Array in New Mexico. The radio data, colored here
in red, reveal extended galactic arms of gaseous hydrogen atoms, which are
raw ingredients for stars. Astronomers are excited that the remote
clusters of baby stars match up with the extended arms, because this helps
them better understand how stars can be created out in the boondocks of a
galaxy.
M83 is located 15 million light-years away in the southern constellation
Hydra.
In the Galaxy Evolution Explorer image on the right, near-ultraviolet
light (or longer-wavelength ultraviolet light) is colored yellow and
far-ultraviolet light is blue. In the combined image at the left,
far-ultraviolet light is blue, near-ultraviolet light is green, and the
radio emission at a wavelength of 21 centimeters is red.