Jupiter and its four largest moons always make for a stunning sight, whether 400 years ago or today. This composite image is not to scale, but shows the moons in their relative positions (from top to bottom: Io, Europa, Ganymede, and Callisto).
NASA/JPL
Thin white clouds crisscrossed the deep-blue sky late in the afternoon of Friday, January 8. As the Sun dipped below the southwestern horizon, I had the eerie feeling that comes from repeating a nearly 50-year-old observing session.
