What causes the Milky Way to appear as a faint, glowing band when viewed from Earth?

Answer

The combined light of billions of stars packed densely into the plane of the galaxy, viewed edge-on.

The visible glow is the accumulated light of countless stars situated within the galactic disk, which we see from our perspective within that plane.

What causes the Milky Way to appear as a faint, glowing band when viewed from Earth?
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