The Kuiper Belt and Olbers's paradox

We investigate the constraints that Olbers's paradox, applied to the zodiac al background as measured from space, sets on outer solar system objects. I f extended to very faint limits, mag, the steep optical R similar to 40-50 number counts of Kuiper Belt objects (KBOs) at R less than or similar to 26 imply an infinitely bright night sky. Small KBOs with radii of r similar t o 1 mum to r similar to 1 km must have a size distribution n(r) proportiona l to r(-a), with a similar to 3.4 or smaller to satisfy the known limits on the sky-surface brightness at optical and far-infrared wavelengths. Improv ed limits on the measured KBO surface brightness can yield direct estimates of the albedo, temperature, and size distribution for small KBOs in the ou ter solar system.