(also Encke’s comet), a periodic comet discovered in 1786 by P.-F.-A. Méchain (France). The Encke-Baklund comet is characterized by a short period of revolution around the sun, which is 3.3 years (its periodicity was determined in 1818). The comet is named after J. F. Encke and O. A. Baklund, both of whom studied the specific features of its motion.
Encke detected the systematic acceleration of the comet (a decrease in the period), which he ascribed to the resistance of the interplanetary medium. Baklund determined that the acceleration was greatest in the period 1858–68, after which it began decreasing rapidly. The acceleration is apparently due to the reactive force that arises when matter flows from the nucleus of the comet as a result of heating by the sun; the direction of this force is deflected away from the sun-comet line because of the rotation of the nucleus about its own axis. The decrease in acceleration is explained by the depletion of volatile substances in the nucleus.
S. V. DOBROVOL’SKII