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Galaxies in Collision

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optical picture of Abell 2142 with x-ray contoursMarch 1, 2000 -- Pictures of a colossal cosmic "weather system" produced by the collision of two giant clusters of galaxies have been captured by NASA's Chandra X-ray Observatory. For the first time, the pressure fronts in the system can be traced in detail, and they show a bright, but relatively cool 50 million degree central region embedded in large elongated cloud of 70 million degree gas, all of which is roiling in a faint "atmosphere" of 100 million degree gas.

Right: The two large elliptical galaxies indicated by arrows in the center of this optical image are thought to be the central galaxies of two merging galaxy clusters. Together, the two merging clusters form a single object astronomers call Abell 2142. The optical image is overlaid with X-ray brightness contours. The bright source in the upper left is an active galaxy in the cluster.



The Chandra data provides the first detailed look at the late stages of this merger process. Previously, scientists had used the German-US Roentgen satellite to produce a broad-brush picture of the cluster. The elongated shape of the bright cloud suggested that two clouds were in the process of coalescing into one, but the details remained unclear. Chandra is able to measure variations of temperature, density, and pressure with unprecedented resolution.

Chandra image of the galactic centerLeft: Chandra X-ray Observatory image of the galaxy cluster Abell 2142. For the first time, the pressure fronts in a system of colliding galaxy clusters can be traced in detail, and they show a bright, but relatively cool 50 million degree central region (white) embedded in large elongated cloud of 70 million degree gas (magenta), all of which is roiling in a faint atmosphere of 100 million degree gas (faint magenta and dark blue). The scale bar in the lower right hand corner indicates one minute of arc, which corresponds to approximately 350,000 light years at the distance of Abell 2142.




Web Links

Chandra home page -from Harvard

Chandra News -from NASA

Galaxy Clusters -a tutorial from Harvard's Chandra home page
