Comet Halley – the most famous of all comets – last visited Earth in 1986. I remember lying on my bed and staring out my bedroom window at it. But even if you were not alive then, you can still see its effects. Every year at this time the earth moves through the trail of dust, ice, and rubble that the comet left behind. These strike Earth’s atmosphere most fully around October 20-22. As it strikes our atmosphere and begins to fall to Earth, the cometary debris vaporizes, leaving bright streaks across a dark night sky known to us as meteors or shooting stars. Thus, every year at this time, as Earth passes through debris left behind by Comet Halley, we on Earth see the Orionid meteor shower.
In 2012, this shower peaks on the morning of Sunday, October 21. It should be pretty good this year as the waxing crescent moon should be set by midnight. Go have a look tonight, the comet itself will not be back until 2061.