A gibbous moon is more than a quarter lit, but not fully so. As the Moon goes from new to full, we say it is 'waxing' (waxing means growing).
What is a waxing gibbous moon? The waxing gibbous moon, is defined to occur when the Moon appears to be more than one-half but not fully illuminated by direct sunlight. Because the fraction of the Moon’s disk that is illuminated is increasing, we consider the Moon to be “waxing.” Each new lunar cycle is measured beginning at each new moon and the waxing crescent moon occurs when the Moon is more than one-quarter but less than one-half of the way around the sky (i.e., along its orbit) from new moon.
Waxing Gibbous Moon Dates / Next Waxing Gibbous Moon
When is the next waxing gibbous moon? A waxing gibbous moon is seen one to two weeks after a new moon. The average calendrical month, which is 1/12 of a year, is about 30.44 days, while the Moon’s phase (synodic) cycle repeats on average every 29.53 days. Therefore the timing of the Moon’s phases shifts by an average of almost one day for each successive month. To find out the waxing gibbous moon dates, please see the waxing gibbous moon calendar below.
Waxing Gibbous Moon and The Moon Phases
The waxing gibbous moon happens when the moon is between a 45 and 90 degree angle with respect to the Earth and Sun. So we are seeing more than half of the moon illuminated and less than half in shadow. The word gibbous refers to phases where the moon is more than half illuminated. “Waxing” essentially means growing or increasing in illumination. Each evening, as the moon’s orbital motion carries it towards the Earth-sun line, we see more of the moon’s day side.
Each lunar cycle begins with a new moon. As the Moon moves eastward away from the Sun in the sky, we see a bit more of the sunlit side of the Moon each night. We call this waxing. After the new moon, the sunlit portion is increasing, but less than half illuminated, so it is a waxing crescent moon. When half of the Moon’s disc is illuminated, we call it the first quarter moon. As the sunlit portion continues to increase, now more than half illuminated, it becomes waxing gibbous moon. When the Moon reaches maximum illumination, a full moon, the Moon has completed one half of the lunar month.
During the second half of the lunar month, the Moon grows thinner each night. We call this waning. The waning gibbous moon phase occurs first, followed by the last quarter moon when half of the Moon’s disc is illuminated. Next is the waning crescent moon, which wanes until the illumination is completely gone; a new moon.