The determination of our galaxy's structure, and our location within the galaxy, was one of the top astronomical highlights of the early 20^th Century. We've learned that, seen from "above" or "below," our galaxy would appear like many of the spiral galaxies we see scattered around the nighttime sky, with a large, densely populated, central region, and trailing spiral "arms." As seen from the side, our galaxy would appear as a thin disk, the dense central region being marked by a "bulge." The overall length of the galaxy, from "end" to "end," is approximately 100,000 light-years, and its thickness is about 10,000 light-years. Our solar system is located on the interior side of one of the spiral arms, approximately 28,000 light-years from the center.

When we see the hazy band of light that we call the Milky Way arching across the nighttime sky, we are seeing the unresolved light of many distant stars along our galaxy's disk. Our galaxy's center lies in the constellation of Sagittarius, which on these mid-November evenings is very low in our southwestern sky; meanwhile, in the exact opposite direction -- towards the constellations of Taurus and Auriga, now rising in our eastern sky -- we are looking "outward" through the galaxy's disk.

As we look away from the Milky Way, i.e., away from the disk, we start to look into intergalactic space. While we do see quite a few stars in these regions, these are for the most part relatively nearby to us (at least when compared with the multitudes of stars we see in the disk). As sky-watchers with even modest-sized backyard telescopes can verify, when we look away from the disk we start to see many dim hazy patches of light that in actuality are distant galaxies; the dust and gas within the disk keeps us from seeing most of the galaxies that might lie in its direction.

Continuing farther, eventually we come to a location where we are looking directly away from our galaxy -- a direction from which someone looking back at us would see our galaxy "face-on." We call such a location a "galactic pole," and there are two such spots: a "north galactic pole," where one can think of us as looking "up" from the galaxy, and a "south galactic pole" where we are looking "down." (Strictly speaking, these are the galactic poles as seen from the perspective of our solar system, rather than from the galactic center itself, but over intergalactic distances this difference is so small as to be entirely trivial.)

The north galactic pole is located in the constellation of Coma Berenices, normally considered a springtime constellation (although it can currently be glimpsed low in the eastern sky shortly before dawn). Near this location, centered in the adjacent constellation of Virgo, is an enormous "cluster" of several hundred galaxies that is in actuality the nearest "large" cluster of galaxies to us. In Coma Berenices itself, and close to the north galactic pole, is an even larger, but much more distant, cluster of galaxies, containing up to several thousand individual galaxies.

The south galactic pole, meanwhile, is located in the dim and obscure constellation of Sculptor, currently visible in our southern sky during the early evening hours, a bit to the south of the moderately bright star Diphda in the constellation of Cetus. While, as one might expect, there are numerous galaxies located in this part of the sky, we don't see much in the way of large clusters of galaxies here like we do around the north galactic pole.

We do see, however, several relatively bright galaxies that collectively form a small but somewhat scattered group of galaxies that is one of the closest such groupings to us -- approximately eight to ten million light-years away. Two of these galaxies -- known as NGC 55 and NGC 253 -- are bright enough to be visible with ordinary binoculars, and in fact the latter of these -- a large spiral galaxy seen almost edge-on -- is one of the brightest galaxies in the entire sky.

To the east, in the adjacent (and equally obscure) constellation of Fornax, one can find a relatively large cluster of galaxies, somewhat smaller and more distant than its springtime counterpart in Virgo. Several of the member galaxies can be viewed with moderate-sized backyard telescopes; the brightest of these, an object known as NGC 1316, appears to represent an example of "galactic cannibalism," i.e., a large galaxy that has gotten bigger by swallowing up nearby companion galaxies. Another of the bright galaxies in the Fornax cluster is the object known as NGC 1365, an impressive spiral galaxy seen almost face-on; several supernovae have appeared in this galaxy over the past few decades, including one as recently as last year.

Closer to home, within both Sculptor and Fornax have been found very tiny galaxies known as "dwarf spheroidal" galaxies, containing at most a few million stars (as compared to the 100 billion or more stars in our own galaxy). The Sculptor and Fornax dwarf galaxies, both of which were discovered in 1938, are located just a few hundred thousand light-years away from us, and are among the closest galaxies to our own. Numerous other such galaxies have been discovered since these two were found, and it is quite clear that these objects represent the most common type of galaxy in the universe, but they are so tiny and dim that we cannot see them once we start looking out over larger distances.

Numerous other objects can be found in the vicinity of the south galactic pole, including a couple of moderately bright star clusters located within our own galaxy. Although this is a rather "blank" area of the sky, at least upon a casual glance, it is clear that detailed study of this region has offered us many clues as to the nature of the universe we inhabit.