Monday, October 10, 2005

Milky Way Bar

In the last few weeks, I got a question emailed from a reader of this blog (wow, I actually have a reader!). The question dealt with a new science report that the Milky Way has a larger bar than previously thought, and the reader wanted to know my opinion on the issue. Well, it's really quite simple. In order to raise flagging sales, the Mars Corporation has increased the size of a Milky Way chocolate bar from 1.2 ounces to 1.44 ounces net weight. (Just kidding!)

Spiral galaxies come in two basic flavors: "barred" and "non-barred." See if you can guess from these two images which is which:

It is hard to know the exact shape of the Milky Way, the galaxy our sun lives in, because we are in it. It is much like being in the middle of a dense forest and trying to figure out what its boundaries look like. In our galaxy, thick dust clouds block our view of the far parts of the galaxy. However, astronomers were able to use some clever techniques of measuring how fast stars are moving through space to deduce that our galaxy had at least a weak bar; perhaps something like this galaxy:

However, infrared light can go through much of this dust. The technology for studying large numbers of stars in the infrared has impoved dramatically over the last decade. Using this infrared light, astronomers were able to determine that our bar is in fact quite significant, perhaps something like this:

In this picture, our sun would be located about halfway between the center of the galaxy and the bright star near the lower right.

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