Holy Smokes!
Where there is smoke, there is fire. And when a galaxy smokes, there is usually a supernova nearby. But this picture of galaxy NGC 891 has astronomers rethinking how galaxies "pollute" their surrounding halos. This edge-on image of the spiral galaxy shows it ejecting dark clouds thousands of light years in extent. The traditional view is that supernova events heat galactic space to temperatures of a million degrees or more, propelling some dust in chimney-like fashion into the outer reaches of the halos that surround galaxies. But the discovery of a massive network of dust clouds in NGC 891 was a surprise and suggests that the picture is more complicated, or that gentler kinds of processes may be at work. One thought: The dust is propelled high into the halo by the gentle pressure of starlight. A similar process occurs when sunlight produces the long tails characteristic of comets.

This image was captured by astronomers using the 3.5 meter WIYN Telescope atop Kitt Peak, Ariz.