What Is a Blue Moon?

A “Blue Moon” is a fairly infrequent phenomenon involving the appearance of an additional full moon within a given period. But which period? It turns out there are two definitions of the term, and one was borne out of a …

Hale-Bopp: The Bright and Tragic Comet

Hale-Bopp was an unusually bright comet that flew by Earth, reaching its closest approach to the planet in 1997. It was most spectacular in the Northern Hemisphere and visible to the naked eye for about 18 months.

Hale-Bopp was probably