Explanation : Is our Galaxy this thin? We believe so. The Milky Way , like NGC 891 pictured above , has the width of a typical spiral galaxy . Spirals have most of their bright stars, gas, and obscuring dust in a thin disk. This disk can be so thin the spiral galaxy appears edge-on like a compact disk seen sideways . The dark band across the middle is a lane of dust which absorbs light. Some of the billions of stars that orbit the center of NGC 891 , however, appear to be moving too fast to just be traveling in circles. What causes this peculiar motion? One hypothesis is that NGC 891 has a large bar across its center - a bar that would be obvious were we to see this galaxy face-on instead of edge-on. This false color picture was constructed from 3 near infrared images.
Media Credits & Attribution
Edge-On Spiral Galaxy NGC 891 Credit and Copyright: J. C. Barentine & G. A. Esquerdo (PSI), 1.3-m Tel., Kitt-Peak, NOAO