Early this week, we will be able to see the first of two supermoons occurring in 2021, known as the “Pink Supermoon”. At this time, the full moon will appear 14 percent larger and 30 percent brighter than usual.
The Moon doesn’t orbit the Earth in a perfect circle, rather an ellipse. This means that during its 27-day orbit, it reaches its furthest and closest points relative to our planet. The closest point is called perigee, and the furthest point is called apogee. When perigee is reached at 11:22 EDT on April 27, 2021, the Moon and Earth will be 357,378 kilometers (222,064 miles) apart rather than the average 384,400 kilometers (240,000 miles). This is what leads to the Moon appearing larger, and the sunlight reflected off it appearing brighter.
The term “supermoon” was created by astrologer Richard Nolle in 1979, referring to a new or full moon occurring within 90 percent of perigee. “Supermoon” is not actually an official astronomical term – the more scientific term for this occurrence is “perigee syzygy”. The word syzygy, derived from the Ancient Greek for “yoked together”, refers to the alignment of three or more celestial bodies in a straight line. During a new or full moon, the Earth, Moon, and Sun are aligned in syzygy.
Unfortunately, the Moon does not actually appear pink during the Pink Moon. This name comes from a list of moon names published in The Old Farmer’s Almanac, which they say “come from Native American, Colonial American, or other traditional North American sources passed down through generations.” The name “Pink Moon” refers to the blooming of the flowering plant "moss pink" or ground phlox (Phlox subulata), one of the first spring flowers. According to NASA, the next full moon on May 26 – known as the Flower Moon – will actually be closer to Earth by 157 kilometers (98 miles).