Comet 103P/Hartley 2, a small periodic comet, was discovered in 1986 by Malcolm Hartley, an Australian astronomer. It orbits the sun about every 6.5 years, and on Oct. 20, the comet will make its closest approach to Earth since its discovery. In this case, "close" means 11 million miles, or 17.7 million kilometers. A moonless sky will make for promising viewing conditions in the northeastern skies, especially just before dawn