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Bruce Murray Space Image Library

Twenty full moons

Twenty full moons
Twenty full moons Visit Laurent Laveder's website for the full-resolution version. This animation is composed of 20 photographs of all of the full Moons from May 2005 to December 2006. The Moon appears to shrink and enlarge and wobble back and forth because its orbit around Earth is inclined and elliptical. The Moon appears smaller when it is farther from the Earth (at apoapsis) and larger when it is closer (at periapsis). The wobbling -- known as libration -- results from the fact that the Moon travels slower near apoapsis than periapsis, while its rotation rate is constant. The wobbling permits Earthly viewers to peek over the eastern and western limbs over the course of a month. The orbit's inclination gives us views over the north and south poles, depending on how high the Moon rises in the sky. The Moon's libration means that a total of 59 percent of the lunar surface is visible from Earth over the course of each month. Laurent Laveder, http://www.photoastronomique.net