From the Galaxy Evolution Explorer website at Caltech:
CARTWHEEL GALAXY MAKES WAVES IN NEW NASA IMAGE
A new image from NASA's Galaxy Evolution Explorer completes a multi-wavelength, neon-colored portrait of the enormous Cartwheel galaxy after a smaller galaxy plunged through it, triggering ripples of sudden, brief star formation.
The false-color composite image, available at http://www.galex.caltech.edu, shows the Cartwheel galaxy as seen by Galaxy Evolution Explorer in ultraviolet light (blue); the Hubble Space Telescope in visible light (green); the Spitzer Space Telescope in infrared (red); and the Chandra x-Ray Observatory (purple). "The dramatic plunge has left the Cartwheel galaxy with a crisp, bright ring around a zone of relative calm," said astronomer Phil Appleton of the California Institute of Technology, Pasadena, Calif. "Usually a galaxy is brighter toward the center, but the ultraviolet view indicates the collision actually smoothed out the interior of the galaxy, concentrating older stars and dust into the inner regions. It's like the calm after the storm of star formation." The outer ring, which is bigger than the entire Milky Way galaxy, appears blue and violet in the image.
What makes this image so interesting is that it's a composite of images of the same galaxy taken from three different observatories.
Who needs an invisible cloud being when the universe is this wondrous?