Nongravitational Forces and Periodic Comet Giacobini-Zinner

Abstract

Observations of P/Giacobini-Zinner could not be successfully represented for more than two successive apparitions using Newtonian equations of motion. The comet's motion has a secular deceleration approximately equal to 0.08 day per (period)2. After extending the differential correction to include nongravitational terms in the equations of motion the observations were successfully represented over the time intervals 1900–1946, 1913–1959, and 1939–1965. There is an indication that the magnitude of the nongravitational forces increases with time and that the motion of the comet was discontinuous between 1959 and 1965. A Giacobinid meteor shower prediction has been provided for the 1972 return.