The winter Milky Way is one of those glorious sights that defy the cold. The view of this magnificent arch of stars across the sky is worth a numb nose and tingling toes.
Most of us can't see the Milky Way from our back yards. Light pollution makes the dim glow from the billions of stars in our galaxy one of its first victims. It's well worth the drive out of town to see the great arch across the sky. It rises from the horizon just below Sirius and Canis Major in the south and stretches through the zenith (directly overhead) and the "w" shape of Cassiopeia before it disappears below the horizon in the north.
All the stars we can see belong to the Milky Way. In fact, there is only one object we can see with just our eyes that doesn't belong to our galaxy: It's our neighbor, the Andromeda Galaxy. It appears as a faint cottony patch below and to the left of Cassiopeia. It's rather low in the northwest at the moment; as the winter passes it will rise higher into more favorable viewing position.
We see the Milky Way as a broad band across the sky because we're looking at it edge-on. The best way to imagine it is to hold a hula-hoop at eye level around your head. Looking straight across - or across the "plane" of the hula-hoop - we see the line of the hoop. When we look up or down, we're looking in and out of the "plane" of the hoop. When we look at the band of the Milky Way, we're looking in the plane of the galaxy; to the left and right we're looking out of the plane. The stars we see still belong to the galaxy, but there are more stars and much brighter ones near the plane.
Where we are: Galaxies come in all shapes and sizes. Our city of stars is a medium-sized spiral or modified spiral. Our solar system is located in the "suburbs" of this "city," about two-thirds of the way out from the center. When we look south in the area of the Milky Way near Orion and Canis Major, we're looking at the "skinny" part - the one-third between us and the outskirts of town.
Conversely, when we look south in the summer toward Scorpius and Sagittarius, we're looking toward "downtown," or into the center of the galaxy.
The Milky Way is one of the many heavenly sights that inspired the ancients. They didn't know what it was, but it resembled familiar things on Earth: rivers, paths, bridges and roads.
The Chinese call it the Tien Ho, or the Celestial River. It still figures prominently in the Japanese celebration of Tanabata, traditionally held on the seventh night of the seventh moon. The Tien Ho divides two lovers, one represented by Vega in the constellation of Lyra and the other by Altair, the bright star in Aquila, the Eagle. Once a year a flock of magpies makes a bridge across the river so the lovers can be together; the meteors of the annual Perseid meteor shower represent the birds.
Mythological origins: The Greeks were responsible for the Milky Way name; their legend says it was milk spilled from Hera's breast when the baby Hercules was fed there (the only way a mortal can become immortal).
The San of the Kalahari desert say the Milky Way came into being when a young girl, alone and frightened during her initiation rite into adulthood, tossed ashes into the sky to become a special, comforting light.
An entirely different and decidedly modern view was taken recently by the orbiting Chandra X-ray Observatory, which turned its instruments toward the center of the galaxy and found a "downtown" full of action. The images show white dwarf stars (the final stage of life of stars like our sun), neutron stars, and black holes lighted by a fog of gas heated to 10 million degrees by a central supermassive black hole. The black hole in the core of our "city" is estimated to contain a mass equal to 3 million suns.
The Chandra, named in honor of the late Indian-American Nobel laureate, Subrahmanyan Chandrasekhar (su/bra/mon'/yon chandra /say/kar), looks at the universe in the X-ray region of the electromagnetic spectrum. X-rays are a much more energetic form of light than the ordinary light we can see. Because of this, the observatory routinely images some of hottest and most explosive areas of the universe.
XEarly notice: For those of you interested in local ancient astronomy, be aware that the Anthropology Colloquium is making plans for the 2002 edition of its popular Mounds Tour. Led by Dr. John White from the Department of Sociology & amp; Anthropology at Youngstown State University, the all-day tour covers some of the most interesting American Indians mounds in southeast Ohio, including the Great Serpent Mound and a pair of snake "solstice" markers discovered by Dr. White. Call the anthropology department at (330) 742-3442.