XMM & R-band imaging of Stephan's Quintet
Credit: Image Courtesy of ESA; X-ray: G. Trinchieri, W. Pietsch, J. Sulentic. D. Breitschwerdt; R-band: C.M. Gutierrez

The Medium is a Message

Stephan's Quintet (named for astronomer Edouard Stephan, an astronomer at the Observatoire de Marseille who discovered it in 1877) is a grouping of 5 galaxies, 4 of which are at the same distance, and one of which is a foreground interloper. The 4 galactic "partners" interact, ripping material from each other. This makes the galaxies poorer, but helps trigger the birth of new stars, and enriches the Intergalactic Medium with complex chemicals. This intergalactic medium is incredibly thin, even though it contains an enormous amount of matter, so that it's difficult to study. Because the IGM is heated from the collisions with the individual galaxies, it radiates copiously in X-rays. The image above left shows X-ray emission contours (as measured by the XMM-Newton X-ray Observatory) superimposed on a red image of Stephan's Quintet, while the image on the right shows the outer contours of the red image superimposed on a "true color" X-ray image. By comparing the X-ray and R-band images, astronomers are able to measure the amount of intergalactic material around the Quintet and to get a better understanding of the ways galaxies in small groups interact and change.

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Page Author: Dr. Michael F. Corcoran
Last modified Friday, 20-Apr-2012 15:23:12 EDT