AstroBob presents: Journey to the Center of Our Galaxy

Amateur astronomer Bob Fisher (better known as AstroBob around these parts–much to his chagrin) has been a passionate star-gazer since childhood when he first saw the superbly dark skies of the Adirondacks on camping trips.  A part-time resident of Olmstedville since 1991, he taught earth science and astronomy in New York City public high schools for more than two decades before making his permanent home here in 2006.  Now a substitute teacher in Warren and Essex county schools, he is also an active astrophotographer. He frequently leads astronomy workshops in local schools and libraries, and occasionally serves as a docent at the American Museum of Natural History in New York City.

The arrival of summer brings to the night sky the most awe inspiring astronomical spectacle of all – The Milky Way. This ghostly band of light spreads across the entire sky from North to South. In early July in the Central Adirondacks, the best time to observe this beautiful luminous band is from midnight until dawn when it rises prominently overhead. Although The Milky Way is observable all year, it attains greatest brilliance during summer, particularly near the southern horizon. Look toward the constellation Sagittarius, where celestial wonders proliferate!

The Milky Way, where we reside, is one of many billions of galaxies that populate the known universe. If we were to travel far out into intergalactic space and peer down, it would be similar to a well formed hurricane as seen from satellite photos with one exception. Instead of an empty “eye” at the center, there would be a fat central bulge packed with stars, gas, and dust. From Earth, the center of our galaxy is obscured by dark nebulae. Although this region appears dark to the human eye, it radiates intensely in radio frequencies of the electromagnetic spectrum. Astronomers have labeled this region Sagittarius A . Strong evidence suggests that the source of this radiation is a gigantic black hole two to three million times the mass of our sun, surrounded by a disk called the event horizon, where all matter and energy including light is greedily swallowed, spiraling inward and disappearing from the known universe.

Our Milky Way is about 100 thousand light years in diameter with half a dozen or so spiral arms radiating outward from the nucleus. Our Solar System resides two thirds from the center in a suburban outlier called the Orion Arm. As our galaxy rotates, it takes our Solar System about 250 million years to make one complete revolution!

The eight brightest stars of the constellation Sagittarius sit right in front of the star-clouds of galaxy central.  Although its name is Latin for The Archer, modern observers sometimes call it the teapot, because it resembles an old fashioned teapot complete with handle on the left ( East ) and spout on the right ( West). This constellation never rises far above the southern horizon at our northern latitude, and as a result of this, it is frequently lost in haze and glare. (To appreciate it in its full glory, go to South America where it rises high in the sky). Despite this, on exceptionally clear nights with transparent sky, I can clearly see the dense glow of the Milky Way.

Space radio telescope Chandra’s image of Sagittarius A at the
center of our galaxy

A good pair of binoculars can greatly enhance the rich detail of this region. The brightest nebula, The Lagoon ( M8 ), just to the right of the “ teapot “ is faintly visible to the naked eye for keen observers. Binoculars reveal a cluster of newly formed stars illuminating the hydrogen gas that feeds them.  Many other nebulae abound along with a multitude of open and globular star clusters. For me, most impressive of all is to pan the region with 10×50 binoculars and see the dark bands of obscuring nebulae interlacing the bright star-clouds.  There is so much more to observe here and it is astounding to consider that you are viewing directly to the center of our home galaxy 70,000 light years away!

Finally, since the invention of the light bulb more than a century ago, artificial night lighting has proliferated exponentially in urban/suburban areas. It amazes me that some city dwellers have never seen the magnificent Milky Way because of the glare from city lights. Unfortunately, they are only able to see   the brightest planets and stars when they look up. Here in the Adirondacks, particularly around wilderness lakes, we still have a rare pocket of our dark sky heritage. I hope we can keep it that way.

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