In a 1984 book co-written with Ann Druyan, Carl Sagan suggested that Earth is at the heart of over a trillion of these objects.
In a 1984 book co-written with Ann Druyan, Carl Sagan suggested that Earth is at the heart of over a trillion of these objects. Freeman Dyson's whacky proposal to terraform these things involves growing giant trees inside of them. "Lost" examples of these things include one named for Wilhelm von Biela. The fragmentation of one of these objects was observed by Eugene (*)  Shoemaker and David Levy. One of these things named for the satellite Encke gives its name to a class of them with an incredibly short period. So-called "long-period" ones may originate from the Oort Cloud. These objects typically consist of a central nucleus and a surrounding "coma" or tail. For 10 points, name these astronomical objects, one of which is named for Edmund Halley.
In a 1984 book co-written with Ann Druyan, Carl Sagan suggested that Earth is at the heart of over a trillion of these objects.
comets