Abstract

Infrared (2–10.3 μm) and visual observations of Comet Halley made prior to perihelion at the Mt. Lemmon Observatory (NASA and U. Arizona) reveal at least three types of short-lived events: (1) On 8 Nov. 1985 (UT) an expulsion of materials resulted in both infrared and visible brightness changes lasting several hours. (2) Between 10 and 13 Jan. 1986 (UT) the comet was observed to increase in brightness by factors of 2.5, 4.3, 4, and 3.8 at wavelengths of 2.3, 3.6, 4.6, and 10.3 μm, respectively. (3) During the same period in January the comet tail underwent a wagging mode, i.e., the position angle first increased by 10° and then decreased by 8°.

© 1986 Optical Society of America