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Period of Comet Hyakutake

The latest orbital analysis (by Don Yeomans at JPL on Mar. 27, 1996 from
radar doppler data for March 24-25 gave the following values to 8 or 9
digits. (His calculations gave even more "significant??" digits.)

e = .999893259
q = .23020359

where e = eccentricity and q = closest approach to the Sun at perihelion
in AU.

I have not seen definitive results for the period of the comet other than
comments in the mass-media. In fact one of the last news reports from
one of the comet sites on the web, put the period at 10,000 years.

But with the above data, I thought I would calculate the semi-major axis
(a) and the period (p) for my Intro to Ast class using Kepler's third law
and a definition of eccentricity.

e = x/(2a) where x = distance between the foci of the orbit
2a = 2q + x => x = 2a - 2q and
e = 1 -(q/a) => a = q/(1-e)

From this result and the above values of q and e, I get

a = 2156.66 AU

Then from Kepler's third law (p^2 = a^3), I find

p = 100,155 yr

Have I made a bad assumption somewhere or is the report of a period of
10,000 yr off by a factor of 10?

Dr. Richard L. Bowman
Dept. of Physics e-mail:
Bridgewater College phone: 540-828-5441
Bridgewater, VA 22812 FAX: 540-828-5479