Side-by-Side Comparison
Click on image for larger view
This ultraviolet image from NASA's Galaxy Evolution Explorer shows the
Southern Pinwheel galaxy, also know as Messier 83 or M83. It is located 15
million light-years away in the southern constellation Hydra.
Ultraviolet light traces young populations of stars; in this image, young
stars can be seen way beyond the main spiral disk of M83 up to 140,000
light-years from its center. Could life exist around one of these
far-flung stars? Scientists say it's unlikely because the outlying regions
of a galaxy are lacking in the metals required for planets to form.
The image was taken at scheduled intervals between March 15 and May 20,
2007. It is one of the longest-exposure, or deepest, images ever taken of
a nearby galaxy in ultraviolet light. Near-ultraviolet light (or
longer-wavelength ultraviolet light) is colored yellow, and
far-ultraviolet light is blue.
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.