Stephen P. Maranworked at NASA for more than 35 years, on projects including the Hubble Space Telescope. He is the author of more than 10 books, includingThe Astronomy and Astrophysics Encyclopediaand Astronomy for Dummies, and is the press officer for the American Astronomical Society. He has an asteroid named for him and has been awarded the NASA Medal for Exceptional Achievement, the George Van Biesbroeck Prize of the American Astronomical Society, and the Astronomical Society of the Pacific's Klumpke-Roberts Award. He lives in Chevy Chase, Maryland.Laurence A. Marschallis the W. K.

T. Sahm Professor of Physics at Gettysburg College and the author ofThe Supernova Story. He is a regular columnist forNatural History, a contributing editor ofSmithsonian Air and Space, andan astronomy contributor forThe World Book Encyclopedia. He is the deputy press officer of the American Astronomical Society and has been published in numerous publications, includingAstronomy,Discover,Harper's,Newsday, andThe New York Times Book Review. He lives in Gettysburg, Pennsylvania.