If your sky is clear - and your horizon unobstructed - start looking toward the west as soon as the sun sets on these May 2013 evenings. You'll find the two brightest planets there: Venus and Jupiter. Then mark your calendar for late May, when the innermost planet Mercury will join the twilight scene. Some are calling the late May event a triple conjunction, and there's a basis for using that name. Another, perhaps more fitting, name for this gathering is planetary trio. Jupiter, Venus and Mercury will form a

planetary trio, meaning they'll fit within a circle whose diameter is less than 5 degrees wide on the sky's dome, on May 25, 26 and 27. May 26 is the closest grouping of these three planets until the year 2021.