EarthSky

July 25th, 2009 - Moon Phases

A waxing gibbous moon appears high in the east at sunset. It’s more than half-lighted, but less than full.

This moon phase comes between one and two weeks after new moon.

The moon has moved in its orbit so that it’s now relatively far from the sun in our sky. A waxing gibbous moon rises during the hours between noon and sunset. It sets in the wee hours after midnight.

People sometimes see a waxing gibbous moon in the afternoon, shortly after moonrise, while it’s ascending in the east as the sun is descending in the west. It’s easy to see a waxing gibbous moon in the daytime because, at this phase of the moon, a large fraction of the moon’s day side is facing our way. Thus a waxing gibbous moon is more noticeable in the sky than a crescent moon, with only a slim fraction of the lunar day side visible. Also, a waxing gibbous moon is far from the sun on the sky’s dome, so the sun’s glare isn’t hiding it from view.

Any moon that appears more than half lighted but less than full is called a gibbous moon. The word gibbous comes from a root word that means hump-backed. You can see the hump-backed shape of the waxing gibbous moon.

As the moon orbits Earth, it changes phase in an orderly way. Follow these links to understand the various phases of the moon.

Waxing Crescent
First Quarter
Waxing Gibbous
Full Moon
Waning Gibbous
Last Quarter
Waning Crescent
New Moon