Milky Way: A Night Sky Wonder

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Milky Way: A Night Sky Wonder

The same new moon that sets up the total solar eclipse Aug. 1 will create dark night-sky conditions for stargazing, making this a great time to check out the beautiful midsummer Milky Way.

Campers and rural residents should have little trouble spotting it, weather permitting.

As soon as darkness falls, the Milky Way becomes evident as a wide glowing arch of variety and beauty, stretching high across the sky from the northeast to southwest.

Sweep with binoculars up from the tail of the constellation Scorpius, low in the southwest through the Summer Triangle, almost overhead and down toward Cassiopeia and Perseus in the northeast. You'll find concentrations of stars, clusters, large apparent gaps such as the Great Rift in Cygnus, and more stars than you thought existed.

Never visible from large cities with their bright lights, smoke and haze, the Milky Way can still be readily viewed from distant suburbs and rural locations. Visually it appears as a faint, albeit distinct ghostly band of light; it almost looks more "smoky" than "milky" in appearance. From a truly dark site, however, it appears in full glory: The brightest portions can cast faint shadows, and it appears highly complex and structured to the unaided eye and like veined marble when viewed with ordinary binoculars.

What it is

Before the invention of the telescope, the true nature of the Milky Way Galaxy ("Gala" is Greek for milk) was a mystery. Now we know it's a concentration of stars in our own galaxy.

The galaxy's center is about 26,000 light-years away toward the Sagittarius star cloud. From where we sit, the galaxy's outer edge is about 20,000 light-years in the opposite direction (toward Auriga and Taurus). We reside on a spur of the Orion arm, and what we see as we look at the Milky Way in our night sky is just a portion of nearest stars between us and the galactic center.

The sun and all the outer stars of the galaxy revolve around the galactic center at the rate of 155 miles per second. It apparently requires about 225 million of our earthly years to make one complete revolution, or one "cosmic year," around the center of our galaxy.

When we began to realize that there were other such vast collections or aggregation of stars, we called them "island universes," but this was an obvious misnomer; since universe means everything there is, it can hardly have a plural. So we've seemed to have settled on "galaxies," which is a compromise as a new meaning for an old word.

What was that eerie cloud?

Unfortunately, because of the tremendous increase in light pollution over the past quarter century, the majority of our current generation have never seen the night sky in all its grandeur.

In his book "Nightwatch," the well-known Canadian astronomer Terrence Dickinson comments that in the aftermath of the predawn 1994 Northridge, California earthquake, electrical power was knocked out over a wide area. Tens of thousands of people in southern California rushed out of their homes looked up and perhaps for the first time in their lives saw a dark, starry sky. In the days and weeks that followed, radio stations and observatories in the Los Angeles area received countless numbers of phone calls from concerned people who wondered whether the sudden brightening of the stars and the appearance of an eerie silvery cloud (the Milky Way) might have caused the quake.

"Such reaction," notes Dickinson, "can come only from people who have never seen the night sky away from city lights."

Joe Rao serves as an instructor and guest lecturer at New York's Hayden Planetarium. He writes about astronomy for The New York Times and other publications, and he is also an on-camera meteorologist for News 12 Westchester, New York.

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