Io and its shadow transit Jupiter overnight this evening, with different stages of the event visible across the U.S. Io and its shadow transit overnight on May 7/8; the pair can be seen crossing Jupiter together shortly after midnight in the Central time zone. Outside this field of view, Callisto lies west of the planet, and Ganymede and Europa are to the east. Credit: Alison Klesman (via TheSkyX) Looking for a sky event this week? Check out our full  Sky This Week  column.  May 6: The Eta Aquariid meteor shower peaks Io, the most volcanic body in the solar system, transits its parent planet Jupiter this evening, beginning just before midnight EDT tonight. Its shadow follows, offering an intriguing sight for telescopic observers.  Jupiter starts the evening in the west, the brightest point of light in the constellation Gemini the Twins, above brighter Venus in Taurus. Because Jupiter sets less than an hour after local midnight, different parts of the U.S.…