JOIN USOur Moon’s many hues
Often, headlines about ‘once in many years’ phases of the moon intrigue everyone. Are these based in science or are they spun out of fancy folklore? Here’s a look.
Full moon and new moon
As the moon reflects sunlight and goes around the Earth, our view of the illuminated part changes every night. In a lunar cycle, we see a completely illuminated ‘full moon’ that progresses to a waning crooked-ball-like gibbous moon, then a half-bright ‘half moon’, followed by a thin crescent of light from the ‘crescent moon’ and then to a dark, invisible ‘new moon’. After this stage, the moon’s phases repeat in the opposite order until we again see the full moon after 29 days from the start. These are the recognised lunar phases.
Supermoon and micro moon
Sometimes, a full moon occurs when the moon is closest to the Earth in its orbit, with the moon appearing bigger and brighter in the sky than an average full moon. Although scientifically called perigee, colloquially it’s known as the ‘supermoon’.
On the other hand, when a full moon occurs with the moon being farthest from the Earth, it is called apogee, or micro moon, and the moon appears smaller and dimmer. Each year, around three to four supermoons occur. Although the supermoon’s proximity slightly affects the ocean tides, it does not cause earthquakes or volcanic eruptions as some believe.
Blood moon
Have you noticed a reddish moon during a total lunar eclipse? That’s a ‘blood moon’ seen when direct sunlight is blocked by the Earth and the only light reaching the moon is the sunlight refracted from the Earth’s atmosphere. However, ‘blood moon’ is not a scientifically-recognised term but is just used in popular articles. A ‘blood moon’ is seen during every total lunar eclipse, which occurs twice a year. Sometimes, due to wildfire smoke up in the atmosphere, the moon appears to be a hue of red or orange, and that is not a blood moon.
Blue moon
This term often implies something that is rare because having four full moons in a three-month period (between a solstice and an equinox) is rare. The ‘blue moon’, however, is the third full moon in a set of four. Of course, there’s no blue tinge on the moon, nor does it have a unique appearance! Typically, blue moons occur once every two or three years.
Black moon
A term coined in 2016, and not used in astronomy, refers to a few new moons in a year, like a second new moon in the same month, or a third new moon in a period between a solstice and an equinox (like the blue moon). The absence of a new moon in February once every 19 years is also considered a black moon event. The next such black moon event will occur in February 2033 and February 2037.
A palette of moon colours
From space, the moon always appears to be brown-tinged grey in colour, but sometimes, due to particles in the atmosphere and how they reflect light, the moon can appear in any of the above colours as documented by an astrophotographer over 10 years from different locations across Italy. When the moon is near the horizon, it appears red or yellow in colour. Fine dust in the atmosphere makes the moon appear blue because of the scattering of light. The purple moon, as captured here, is still a mystery to scientists and they believe a combination of factors could have resulted in that unique colour.