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Release Date: 2006/01/11
This false-color composite image shows the Cartwheel galaxy as seen bythe Galaxy Evolution Explorer's Far Ultraviolet detector (blue); theHubble Space Telescope's Wide Field and Planetary Camera-2 in B-bandvisible light (green); the Spitzer Space Telescope's Infrared ArrayCamera (IRAC) at 8 microns (red); and the Chandra X-ray Observatory'sAdvanced CCD Imaging Spectrometer-S array instrument (purple).
Approximately 100 million years ago, a smaller galaxy plunged throughthe heart of Cartwheel galaxy, creating ripples of brief starformation. In this image, the first ripple appears as anultraviolet-bright blue outer ring. The blue outer ring is so powerfulin the GALEX observations that it indicates the Cartwheel is one of themost powerful UV-emitting galaxies in the nearby universe. The bluecolor reveals to astronomers that associations of stars 5 to 20 timesas massive as our sun are forming in this region. The clumps of pinkalong the outer blue ring are regions where both X-rays and UVradiation are superimposed in the image. These X-ray point sources arevery likely collections of binary star systems containing a blackhole(called Massive X-ray Binary Systems). The X-ray sources seem tocluster around optical/UV bright supermassive star clusters.
The yellow-orange inner ring and nucleus at the center of the galaxyresult from the combination of visible and infrared light, which isstronger towards the center. This region of the galaxy represents thesecond ripple, or ring wave, created in the collision, but has muchless star for mation activity than the first (outer) ring wave. Thewisps of red spread throughout the interior of the galaxy are organicmolecules that have been illuminated by nearby low-level starformation. Meanwhile, the tints of green are less massive, oldervisible light stars.
Although astronomers have not identified exactly which galaxy collidedwith the Cartwheel, two of three candidate galaxies can be seen in thisimage to the bottom left of the ring, one as a neon blob and the otheras a green spiral.
Previously, scientists believed the ring marked the outermost edge ofthe galaxy, but the latest GALEX observations detect a faint disk, notvisible in this image, that extends to twice the diameter of the ring. |
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