Practically overhead this week at 9:30 p.m. is a dark, dim region of sky that figures very prominently in astronomical observation and research. To the naked eye its appearance is undistinguished. There are no bright stars or distinctive constellations here, but it is bracketed by four prominent star groups, which make it easy to isolate.
To its west we find the constellation Leo the Lion, just beginning his descent toward the horizon. You can't miss the sickle-shaped asterism that forms the lion's head, with Regulus as the handle star. To the east is ruddy Arcturus in Bootes, brightest star in the northern nighttime sky. High in the north, the Big Dipper lies cup down, its crooked handle pointing back toward Arcturus. And if we continue on that arched course through Arcturus further south, we come to yet another star, blue-white Spica in Virgo the Virgin, which is approaching the meridian.
Practically on the meridian at this time is a point in the sky called the North Galactic Pole, a point marking the north pole of our galaxy. (There is also a South Galactic Pole, which is in the opposite part of the sky in the constellation Sculptor.) The North Galactic Pole lies a little north of a line between Arcturus and Denebola, the star representing Leo the Lion's tail. You won't find a bright star marking the galactic pole's location, although, if your skies are dark enough, you will see a faint scattering of stars in this proximity, marking the rarefied constellation Coma Berenices.
This unassuming piece of sky is our cosmic window onto a universe
that lies well beyond the confines of our galaxy. The reason this area appears so starless is because our line of sight passes through the thinnest part of the Galaxy, in which there are very few stars between us and the more remote universe beyond.
As mentioned earlier (January 11 - 17), our galaxy is shaped something like a wafer. When we look through the plane of the wafer, as we do during the summer and winter months, we see lots of stars. The luminous band of the Milky Way stretching across the sky is essentially our view through the nearby portions of this disk. In the spring and fall months, however, our nighttime view is perpendicular to the plane of the Galaxy. It's like looking up at the sky from a clearing in the forest rather than looking through the dense trees. When we look in this direction, our view is out of the thin part of the disk and deep into intergalac-tic space.
Although it may look as if there's nothing of interest to see in this direction, close scrutiny with a 6- to 10-inch telescope at low magnification reveals otherwise. On a clear moonless night away from the light glow of the city, slowly scan the region east and a little south of Leo's hindquarters and you will occasionally see faint, fuzzy patches of light interspersed among the stars. Sometimes, you may even see two and three together in the same field of view. These ghostly glows - some round and some oval - are actually other galaxies, tens of millions of light-years away. Each contains hundreds of billions of stars. It is conceivable that some of these stars may have planets and that a select few planets may harbor lifeforms of one type or another. And there are billions of galaxies in the universe.
Because the light we see from these galaxies tonight actually left them tens of millions of years ago, this view forms a kind of cosmic window in time as well as space. The distance the light traversed is so great that it is only now reaching us. We see the galaxies as we might see dinosaurs walking across ancient continents in a time before they vanished from the face of the earth.
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