NASA's Chandra Finds Black Holes Stirring Up Galaxies
Chandra images of 56 elliptical galaxies have revealed evidence for unsuspected turmoil. As this sample gallery of X-ray (blue & white) and optical (gray & white) images shows, the shapes of the massive clouds of hot gas that produce X-ray light in these galaxies differ markedly from the distribution of stars that produce the optical light.
Except for rare cases, most violent activity in isolated elliptical galaxies was thought to have stopped long ago. Elliptical galaxies contain very little cool gas and dust, and far fewer massive young stars which explode as supernovas. Thus it was expected that the hot interstellar gas would have settled into an equilibrium shape similar to, but rounder than that of the stars.
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Image credit: X-ray: NASA/CXC/U. Ohio/T.Statler & S.Diehl; Optical: DSS