March 1, 2001: The Hubble telescope has snapped this remarkable view of a perfectly "edge-on" galaxy, NGC 4013. This new Hubble picture reveals with exquisite detail huge clouds of dust and gas extending along, as well as far above, the galaxy's main disk. NGC 4013 is a spiral galaxy, similar to our Milky Way, lying some 55 million light-years from Earth in the direction of the constellation Ursa Major. Viewed face-on, it would look like a nearly circular pinwheel, but NGC 4013 happens to be seen edge-on from our vantage point. Even at 55 million light-years, the galaxy is larger than Hubble's field of view, and the image shows only a little more than half of the object, albeit with unprecedented detail.
This edge-on view reveals that galaxies are thin, pancake-shaped objects. Most of the dust clouds lie in the galaxy's plane, forming the dark band, about 500 light-years thick. This dark band appears to cut the galaxy in two from upper right to lower left. A similar effect can be seen in our own sky. If one views the Milky Way Galaxy by going well away from city lights, dust clouds in the disk of our own galaxy appear to split the glowing band of the Milky Way in two. The dark clouds stand out in the picture because they absorb the light of background stars. By studying the color and the amount of light absorbed by these distant clouds in NGC 4013, astronomers can estimate the amount of matter in them.
These dark clouds are believed to be where new stars are formed. Later, when the dust disperses, the young stars become visible as clusters of blue stars. NGC 4013 shows several examples of these stellar kindergartens near the center of the image, lying in front of the dark band along the galaxy's equator. The extremely bright star near the upper left corner, however, is a foreground star belonging to our Milky Way Galaxy.