A waxing gibbous moon is an intermediate phase of the lunar cycle that starts right after the first quarter moon (half-moon) and lasts until it becomes a full moon.
Fourth phase of the lunar cycle
A waxing gibbous moon is the fourth phase of the lunar cycle, as it comes after a new moon, a waxing crescent moon and a first quarter moon.
The meaning of a waxing gibbous moon
A waxing gibbous moon consists of two terms: waxing and gibbous.
“Waxing” means increasing or growing. After a first quarter moon, the illuminated area of the moon increases day by day until it becomes a full moon. That’s why it’s called a waxing moon.
The illuminated area of a waxing gibbous moon increases from 50% to 100%.
“Gibbous” comes from a Latin word “gibbosus” that means “hump-backed”. The moon looks like a hump-back or convex shape between a first quarter moon and a full moon. That’s why it’s called a gibbous moon.
So a waxing gibbous moon indicates the shape of the moon.
Rise and set time of a waxing gibbous moon
A waxing gibbous moon rises in the afternoon (between noon and sunset), reaches its highest point in the sky (overhead point) in the evening, and sets after midnight (between midnight and sunrise).
Please remember, a waxing gibbous moon does not rise and set at the same time every day. On consecutive days, a waxing gibbous moon rises and sets about 50 minutes later.
A waxing gibbous moon is visible in the daytime
Like a first quarter moon, a waxing gibbous moon is also visible in the afternoon because the sunlight reflected from a waxing gibbous moon is bright enough to be seen against the daytime blue sky.
The duration of a waxing gibbous moon
The moon takes about 29.5 days to complete a lunar cycle.
Now, a lunar cycle has eight phases in total. These are the new moon, waxing crescent moon, first quarter moon, waxing gibbous moon, full moon, waning gibbous moon, third quarter moon, and waning crescent moon.
Four primary phases (new moon, first quarter, full moon, and third quarter) have no duration as they occur at a specific moment in time.
So the duration of four intermediate phases (waxing crescent, waxing gibbous, waning gibbous, and waning crescent) is 29.5 days in total.
So the duration of a waxing gibbous moon is about 29.5/4 = 7.3 days.
Looks opposite in opposite hemispheres
A waxing gibbous moon appears as a hump-back or convex shape in the sky from anywhere in the world. Its percentage of illumination is also the same. However, it looks opposite in opposite hemispheres.
In the northern hemisphere, more than the right half of the moon is visible, and in the southern hemisphere, more than the left half of the moon is visible.
People living in the southern hemisphere (south of the equator) observe the same waxing gibbous moon from opposite angles than the people living in the northern hemisphere (north of the equator). As a result, a waxing gibbous moon looks upside down.
The appearance of the Golden Handle
The Golden Handle (a bright arc) is an optical feature on the lunar surface, visible through a pair of binoculars or a telescope about 10 days after the new moon, when the moon is in its waxing gibbous phase.
The Golden Handle is visible on the lunar terminator (lunar day-night boundary) when the yellowish sunlight reflects from the peak of Montes Jura (a mountain range), while Sinus Iridum (Bay of Rainbows) is still in darkness.
Read about all eight phases of the moon:
New moon
Waxing crescent moon
First quarter moon
Waxing gibbous moon
Full moon
Waning gibbous moon
Third quarter moon
Waning crescent moon
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