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Galactic Sweep

October 8, 2010

The two extremes of the Milky Way galaxy are in view this evening -- the crowded downtown and the sparsely populated hinterlands. They're connected by a hazy bridge of light that gets thinner and fainter as it arcs away from the galactic center.

The galaxy's "downtown" is in the southwest at nightfall. It's to the upper right of the "spout" formed by teapot-shaped Sagittarius.

Under dark skies, away from city lights, you'll see some relatively bright regions of the Milky Way there, separated by darker regions. The bright areas are the combined light of millions of stars. The darker areas are clouds of dust, which block the light of the stars behind them. The galaxy's core is in one of these darker lanes, so we can't see it directly. But at least we can see where it is -- surrounded by rich clouds of stars.

By around 10 or 11, as the center of the galaxy stands just above the horizon, the point that's directly opposite the center is rising in the east. It's near El Nath -- the star that marks the tip of one of the horns of Taurus, the bull.

If you follow the arch of the Milky Way across the sky from Sagittarius to Taurus, you'll see that there's a big difference. That's because you're moving away from the center of the galaxy toward its rim, where there are far fewer stars. Over the coming months, that part of the galaxy will climb higher each night, showing us a part of the Milky Way that lacks the bright lights of downtown.


Script by Damond Benningfield, Copyright 2010


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