The Pink Moon is one of the most recognizable names given to a specific full moon, adopted globally. This annual event refers to the full moon that appears in the spring, marking a moment in the lunar calendar with historical and cultural significance.
Visual Appearance of the Pink Moon
Despite its enchanting name, the moon does not actually turn a vibrant rose color during this time. The full moon in question will typically display the same hues as any other full moon, appearing as a bright white or silvery disk when it is high overhead. Its color remains consistent with the lunar surface’s natural albedo, or reflectivity.
Any reddish, orange, or yellow tint observed is not unique to the Pink Moon but is instead caused by Earth’s atmosphere. When the moon is near the horizon, its light must travel through a greater amount of the atmosphere to reach an observer’s eye. This phenomenon, known as Rayleigh scattering, causes shorter wavelengths of light, like blue and violet, to be scattered away.
The remaining light that passes through the dense atmosphere consists of longer wavelengths, which fall on the red and orange end of the visible spectrum. This explains why the moon often appears a warm, golden color at moonrise or moonset. The visual spectacle is therefore one of atmospheric optics, not a change in the moon’s inherent color.
Why Is It Called the Pink Moon
The origin of the name “Pink Moon” is rooted in traditional North American Indigenous and Colonial American culture. Full moon names historically served as a calendar for tracking seasons and activities, based on a terrestrial event that coincides with the moon’s appearance.
Specifically, the designation comes from the common name for the Phlox subulata, or creeping phlox, a species of wildflower native to the eastern United States. This plant is one of the earliest to bloom in the spring, covering the ground with blankets of vibrant, mossy pink flowers. The timing of this bloom aligns closely with the arrival of the full moon in spring.
Various Eastern Native American tribes, including the Algonquin, used this natural sign of spring’s return to name the full moon. While the Pink Moon is the most widely recognized name today, the same full moon has also been known by names like the Sprouting Grass Moon or the Egg Moon in other traditions.
When to See the April Full Moon
Astronomically, the Pink Moon is the full moon that occurs during April. A full moon is defined as the precise moment when the Moon is positioned exactly 180 degrees opposite the Sun in celestial longitude. For observers on Earth, the moon appears fully illuminated for approximately a day before and after this exact moment.
For the best viewing experience, observers should look toward the eastern horizon immediately after sunset. At this time, the moon is just rising, which is when the atmospheric effects make it appear largest due to the Moon illusion and give it a golden hue. Similarly, the moon will appear large and colorful just before it sets in the west before sunrise.
The lunar cycle dictates that the full phase occurs roughly every 29.5 days, meaning the April full moon will appear on a slightly different date each year. Locating the exact moonrise time for a specific location is the most effective way to ensure a clear view of the entire, brightly illuminated disk.