The full moon of May, called the Flower Moon, will occur in the eastern U.S. during the evening hours of May 12. Two days later, the just-past-full moon will occult the star Antares.
Moons are full when they are on the opposite side of Earth from the sun, and fully illuminated (from the point of view of Earth). They happen every 29.5 days, but this is actually slightly longer than the time it takes the moon to complete one revolution around our planet, which is 27.3 days. The reason is the movement of Earth around the sun; in the time it takes the moon to circle around Earth, our planet has moved a short distance along its orbit (a bit less than one twelfth of the way), so the moon has to go a little further to get to the opposite side of Earth from the sun.
