Disruption of giant comets in the solar system and around other stars

In a standard cometary mass distribution (dN/dM) alpha M(-a), a = 1.5 to 2.0) most of the mass resides in the largest comets. The maximum mass M sub max for which this distribution holds uncertain but there are theoretical and observational indications that M sub max is at least approx. 10(23)g. Chiron, although formally classified as an asteroid, is most likely a giant comet in this mass range. Its present orbit is unstable and it is expected to evolve into a more typical short period comet orbit on a timescale of approx. 10(6) to 10(7)yr. The breakup of a chiron-like comet of mass approx. 10(23)g could in principle produce approx. 10(5) Halley-size comets, or a distribution with an even larger number. If a giant comet was in a typical short period comet orbit, such a breakup could result in a relatively brief comet shower (duration approx. less than 10(6)yr) with some associated terrestrial impacts. However, the most significant climatic effects may not in general be due to the impacts themselves but to the greatly enhanced zodiacal dust cloud in the inner Solar System. (Although this is probably not the case for the unique K-T impact). Researchers used a least Chi square program with error analysis to confirm that the 2 to 5 micrometer excess spectrum of Giclas 29 to 38 can be adequately fitted with either a disk of small inefficient (or efficient) grains or a single temperature black body. Further monitoring of this star may allow discrimination between these two models.