Astronomers have, for the first time, spotted a planet that is considered to be in the "Goldilocks zone," meaning that its environment is just right to sustain life: not too hot, not too cold. Scientists approximate that...

This site describes soft gamma repeaters. The author, Robert C. Duncan of the University of Texas at Austin, explains how these strange, physically-extreme stars form, and why they emit steadily pulsating X-rays with...

In honor of the 50th anniversary of Apollo 11 this July, the BBC World Service has produced this in-depth podcast series detailing "the dramatic, definitive story ... about the men and women who reached for the moon." 13...

This NASA Image of the Day is the first image of the Earth and moon in a single photograph. The image was captured 7.25 million miles from Earth by Voyager 1 in 1977. More information about the photograph and a link to...

This resource covers Seyfert galaxies, radio galaxies, BL Lacertae (BL Lac) objects, quasars, supermassive black holes, determining masses in galactic centers using the virial theorem, and a model for active galactic...