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Sky Watch: Milky Way's hazy appearance

I'm never surprised when, at summer star parties, someone looks skyward after dark and exclaims: "Looks like clouds are moving in . . . think we'll be heading home now." Of course, the "clouds" they're seeing are something they've rarely or never seen: the Milky Way.

Now, as hopefully frequent stargazers, I'm sure you think I'm exaggerating. But I swear it's true. Many people just don't spend enough time under a dark, starry sky to recognize even the most common of celestial phenomena. And the Milky Way is, without a doubt, one of the most common, if not beautiful, sights in all the heavens.

June is a perfect time to begin watching the Milky Way from a rural un-light-polluted area. Not long after dark right now, you'll see it appear to flow "milkily" from south to north above the eastern horizon.

On its southern end, it passes by the large constellation Scorpius, the scorpion, and on the northern end weaves through the region of Cassiopeia, the queen. High in the east, it splits the famous Summer Triangle, made up by the bright stars Vega, Deneb and Altair.

What we are seeing is the rim of our galaxy's disk arching across the sky; its hazy appearance, of course, is just an illusion caused by so many stars at such great distances that the human eye cannot perceive them as individual points of light.

The first thing you'll notice about the Milky Way is that it's not uniform in brightness. It is mottled with dark rifts along its entire length. These are known to astronomers as Giant Molecular Clouds -- or GMCs -- massive globs of interstellar dust that stand in stark silhouette against the Milky Way's brighter stellar band. It is within these GMCs that massive star- and planet-forming regions exist, hidden from eyes not privileged enough to be peering with infrared telescopes. Many Native American Indian tribes believed the Milky Way to be a road that led the souls of the recently departed to their final resting places. The seafaring Polynesians saw it, instead, as a great blue shark. But it was the ancient Greeks who described its appearance as that of milk spilled across the heavens, and that led to the name we use today.

While you're gazing at the Milky Way, don't just limit yourself to viewing with your eyes. Binoculars reveal countless stars, star clusters and gaseous nebulae invisible to the eye -- "deep sky" objects that just beg to be studied further with a small backyard telescope.

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