How does the composition of a star affect the temperature? In 1925 a young woman solved this puzzle in her doctoral thesis. Her analysis was a great breakthroughs in astrophysics. Otto Struve described it as “the most brilliant Ph.D. thesis ever written in astronomy.”

The objects in the Messier catalog that are the farthest south are two star clusters. M6 is also called the Butterfly Cluster and M7 is also known Ptolemy's Cluster. They're splendid objects seen in their glory in the southern skies, but if you live in the far north you can't see them at all.

Chamaeleons lived in lands exotic to 16th-century Europeans. Yet although color-changing lizards are fascinating, Chamaeleon the constellation is a small, dim southern sky constellation with no associated mythology. Why does it even exist? Is there anything of interest there?

What sort of tie would you give a cosmic father? What would you feed him? Where might he find challenging mountaineering, make an astounding golf shot or get up an interstellar soccer game? How can you send a special man a genuinely galactic greeting? Here's how.

Each day for six months after the winter solstice, the Sun rises a bit higher in the sky. It reaches the maximum height at the summer solstice, the longest day. Evidence of rituals and festivals at the times of the solstices goes back thousands of years.

It's the place where time begins: The Royal Observatory, Greenwich, England. Here you can stand on the Prime Meridian of the world with one foot in the western hemisphere and the other in the eastern hemisphere. It represents over three hundred years of astronomical and maritime history.