2021’s first supermoon, the ‘Pink Moon,’ will rise on Tuesday. It won’t be pink.

The firstsupermoon of 2021 is happening on Tuesday.
April’s full moon is named the “Pink Moon,” and will be among the brightest and biggest of the year.
It won’t necessarily be pink.
Supermoons are full moons that happen when the moon’s orbit brings it closest to Earth.

The first supermoon of the year will happen Tuesday, appearing up to 30% brighter and 14% bigger than a typical full moon.

It’s the first of two supermoons in 2021: Another is coming down the pike in May. The two moons are “virtually tied” in terms of size and brightness, according to NASA.

April’s full moon is known as the “Pink Moon,” though that doesn’t necessarily mean it will shine pink in the sky. The nickname comes from a pink spring flower found in North America, according to The Old Farmer’s Almanac.

Supermoons happen when the moon’s orbit brings it closest to Earth
Astronomers don’t love the moniker “supermoon,” and tend to squabble over which full moons qualify as supermoons. An astrologer coined the term in 1979.

Generally, a supermoon refers to a full moon that occurs when the moon is within 90% of its perigee – the point of the moon’s orbit that brings it closest to Earth. According to NASA, supermoons happen a few times a year at most.

The moon’s 27-day orbit around the Earth looks like an ellipse, rather than a circle, due to gravity from the sun and Earth pushing and pulling on the moon as it travels through space. So there are points along its orbital path that bring the moon closer or farther away from our planet. (Think of a rubber band around a ball: If you pull both ends, it makes an oval, so two sides get closer to the ball, while the ends get farther away.)

When the moon hits perigee, it gets within 360,000 kilometres of Earth. (Usually, it’s 380,000 kilometres away.) That difference in distance will make a supermoon appear brighter and bigger than a usual full moon, though the change is difficult to detect with the naked eye.

To best see the supermoon, experts recommend heading outside either just after moonrise, when the moon is low, or as the moon is setting. Full moons that are higher up in the sky look dimmer and smaller than moons close to the horizon.

If you miss this supermoon, though, don’t worry – the next one is 26 May. NASA said the May supermoon, known as the Flower Moon, will be 160 kilometres closer to Earth than the pink supermoon.

The Pink Moon probably won’t look pink
April’s Pink Moon is named after the pink creeping phlox plant common in the Eastern US. It has also been called the Sprouting Grass Moon, the Egg Moon, and the Fish Moon, according to NASA.

But the nickname is misleading: The moon is always the same colour, and likely won’t look pink when it rises Monday.

Sometimes, the moon can appear pink as it’s rising due to oxygen and nitrogen particles in Earth’s atmosphere.

Oxygen and nitrogen are better at scattering colours made by certain kinds of light – colours with shorter wavelengths, like blue or violet – while colours with longer wavelengths like red, orange, or yellow are left behind. So when the moon sits low on the horizon, where the atmosphere is thickest, those longer wavelength colours dominate what you see, sometimes giving the moon a pinkish hue.