The dilemma of the new-comet flux

The question of the constancy of the flux rate of 'new' comets from the Oort cloud is critical in studies of the origin of comets. The large numbers may be explained by our being in a 'comet shower' or else by a loss of intrinsic brightness by new comets during their first passage through the inner solar system-hence the dilemma. Improvements in the quality and quantity of reliable orbits now make possible fairly precise evaluation of the data involved in the dilemma and a realistic comparison of the two alternatives. If we are in a comet shower, the increase with respect to the last several tens of thousands of years is not more than a factor of 1.8 nor a magnitude loss during first passage of more than 0.85 mag. This applies if new comets are defined as those with periods greater than 10(exp 6) yr. If the limit is set at 2.8 x 10(exp 6) yr, we may not be really in a comet shower and a good fraction of the comets with periods in the range P greater than 10(exp 6) and less than 2.8 x 10(exp 6) yr may be returning comets. The Oort cloud would then be fairly stable to nearly 40,000 AU. If we assume the reality of comet fading in the sense that few new comets are observable on their returns when more distant than 3.0 AU from the Sun, and if we then limit the discussion to comets with perihelion distance q less than 3.0 AU, there is no evidence for a shower.