Monday, June 13, 2005

Am I blue?

A story posted on talks about the "discovery" of blue galaxies in voids, or large regions of the universe that have few galaxies. The result itself, which you can read about in the article, isn't unexpected, but it makes for a good lesson on the structure of the universe.

Shortly after the Big Bang, the Universe was almost perfectly smooth, with "almost" being the key word. Some parts had slightly more matter than others, some had slightly less. Over the 13 billion years the Universe has been around, the extra pull of gravity in the slightly denser areas pulled much of the material in the universe over, creating a pattern of galaxies that looks like the foam in a bubble bath. "Voids" are the spaces in the middle of these bubbles -- there isn't much there!

Since galaxies in voids are alone and mainly untouched since they formed, studying these galaxies helps astronomers to understand how galaxies grow, form stars, and change when nothing else is around. Since most galaxies are not in voids, but live near other galaxies in groups (a handful of big galaxies) or clusters (a swarm of hundreds of galaxies), any differences between the galaxies in voids and all other galaxies are likely due to interactions between galaxies. This includes galaxy harassment and galaxy collisions.

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