Observations of periodic comet d'Arrest in 1678 and implications for its evolutionary history

The identity of comet 1678 La Hire with P/d'Arrest is demonstrated, which makes this the oldest known observation of a short-period comet of the Jupiter family. Different modifications of linkages of the strongly perturbed orbit over 25 unobserved perihelion passages, and four close encounters with Jupiter, are applied and evaluated. The best one, starting with the 1851 osculating orbit and assuming constant nongravitational forces in the past, represents the 1678 observations to +/- 0-degrees-2, well within their positional uncertainty. At the same time, the 1989 perihelion passage is represented to 0-degrees-01. Since the fitted A2 parameter is about the average of the mean value from the period 1851-1989 (4% lower) and the value obtained with a statistically significant term for the varying perihelion distance (5% higher), the nongravitational accelerations appear to be extraordinarily stable. This peculiarity is tied to an uniquely strong recurrent perihelion asymmetry of the light curve. The observations of P/d'Arrest from 1678 imply that at that time, 47 revolutions ago, both its absolute brightness and the shape of its light curve were the same as at present, within the range of observational accuracy.