This month, during the morning hours of the 19th, skywatchers can see a waning gibbous Moon pass in front of the first-magnitude star Aldebaran. This event-called an occultation (from the Latin for "hiding")-is the seventeenth in a series that started in August 1996 and will end on February 14, 2000. During the late evening hours of the 18th, note how quickly the Moon (three days past full) approaches the orange star: about a full Moon's width per hour. To witness the actual occultation you'll need binoculars, as the Moon's glare will overwhelm Aldebaran for naked-eye viewers. Aldebaran disappears behind the bright (forward) edge of the Moon and, about an hour later, emerges from behind the unlighted (and unseen) part of our satellite. As though a switch were turned on, the star reappears.
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