No. 35: Sep-Oct 1984
Halley's Comet, still a billion kilometers away, is just beginning to emit gases at the urging of the sun's rays. It should, therefore, be getting brighter -- and it is -- but its brightness pulsates. A French team of scientists, led by Jean Lecacheux, has determined that Halley's Comet flares up at regular intervals just over 24 hours apart. We usually do not study comets carefully until they are very close to the sun, so we don't know if this blinking behavior is typical or not. The most reasonable explanation is that Halley's Comet rotates about every 24 hours and that its surface is not uniform. One portion of its surface may be brighter or emit more luminous gases than the rest. In any event, we have a new astronomical curiosity.
(Lloyd, Andrew; "Halley's Comet Is Blinking," New Scientist, p. 20, May 24, 1984.)
Reference. Cometary outbursts are cataloged at ACO20 in The Sun and Solar System Debris. This Catalog volume is described here.