As Saturn slowly makes it retreat into the glare of the Sun in the western sky, Jupiter begins to move toward center stage. Saturn continues to remain visible for an hour or two following sundown. But by the end of July, it will be too low to give a steady view.

Rising before midnight, Jupiter is already a dazzling beacon in the eastern sky. By the end of the month, Jupiter will rise in evening twilight as it nears opposition with Earth on August 14. The solar system's two largest planets serve as celestial bookends for the brilliant white star Spica in the constellation Virgo and the super red giant star Antares in Scorpius.

A binocular view of Jupiter will often reveal its four largest moons —Io, Europa, Ganymede and Callisto. Also known as the Galilean moons, these bright points of light gave Galileo the evidence that ultimately unseated Earth as the center of celestial motion.

To further his exploration of the starry deep, Galileo sought the patronage of the powerful and wealthy Medici family. In 1609, when his former student, Cosimo Medici became Grand Duke of Tuscany, Galileo seized the opportunity by sending a letter to the Duke announcing his discovery. He wrote that "since it is up to me, the first discoverer, to name these new planets, I wish, in imitation of the great sages who placed the most excellent heroes of that age among the stars, to inscribe these with the name of the Most Serene Grand Duke."

Ever diplomatic, Galileo sought the opinion of the Grand Duke's secretary to help choose which name to use for his discovery. Galileo proposed two names — Cosmica Sidera (the Cosmian stars) and Medicea Sidera (the Medician stars.)

The duke's secretary suggested he use the name Medicea Sidera to honor all four brothers of the Medici family. Galileo made the names public in his March 1610 issue of Sidereus Nuncius (The Starry Messenger).

The names we use today are attributed to German astronomer Simon Marius who claimed to have discovered the moons at the same time as Galileo. Marius named the moons after mythological lovers of Zeus. Galileo never recognized Marius' names preferring instead to use a number for each moon in his observation log.

• Tonight, I will offer a presentation at the Vista Grande Public Library 14 Avenida de Torreon in Eldorado. I will share practical stargazing tips to help you find your way around the night sky. The program begins at 8 p.m. Admission is free. For more information, call 466-7323.

• Also, mark your calendar for July 18 and make plans to join members of the Capital City Astronomy Club and the Santa Fe Conservation Trust for "Trails and Telescopes at the Galisteo Basin Preserve". The event runs from 4:30 to 10 p.m. and includes hiking and mountain biking opportunities in the afternoon followed by a BBQ dinner catered by the Cowgirl Hall of Fame and stargazing in the evening. Costs are $22 for adults and $12 for kids (12 and under). Advance purchase required. For more information and to register, visit the Web site at www.sfct.org or call 989-7019.

Peter Lipscomb shares the wonder of the night sky as lead guide for Astronomy Adventures and works to promote sensible and energy efficient lighting practices. Contact him at pslipscomb@gmail.com.