Large, brilliant lunar spectacles will bookend the month of August as the moon approaches its nearest point to Earth. This month will feature twin rare supermoons, which occur when the moon reaches this point in its orbit while also appearing full.
According to calculations by retired NASA astronomer Fred Espenak, the first of the supermoons will peak at 2:32 p.m. ET on Tuesday. This means that lunar gazers in Europe, the United Kingdom, Africa, and the Middle East will be able to see the moon at its brightest in the night sky at a distance of approximately 222,158 miles (357,530 kilometers) from Earth. Observers in the United States can rest assured that the moon will appear round on August 1 evening. Due to their proximity, supermoons appear brighter and larger than other full moons, though this is not always visible to the unaided eye.
According to The Old Farmer’s Almanac, the full moon this week is also known as the “sturgeon moon” because it occurs around the time of year when the large freshwater fish were historically abundant in the Great Lakes. Tuesday evening, after sunset, the sturgeon supermoon will be most visible in the United States when viewed from the southeast.
Then, on August 30, a full moon will appear at the closest point to our planet this year — approximately 222,043 miles (357,000 kilometers) away — creating a rare super blue moon.
The term “blue moon” refers to the rare occurrence of a second full moon within the same calendar month, which occurs approximately once every two and a half years. For example, the most recent blue moon occurred in October 2020.
The apex of the super blue moon on August 30 will occur at 9:36 p.m. ET, according to the almanac. The celestial orb will also be visible on the evening of August 31, barring any adverse local weather conditions.
However, it will not appear blue despite its appellation. According to the Encyclopaedia Britannica, the term originates from a 16th-century expression in which a blue moon referred to something that never — and later infrequently — occurred.
What Are Supermoon, Blue Moon, And Full Moon?
When the near side of the moon is entirely illuminated by the sun in the night sky, a full moon occurs. This typically occurs once per month.
Supermoons are less frequent.
These lunar phenomena occur because the moon does not orbit the Earth in a precise circle. Rather, the moon’s orbit is elliptical in shape, bringing it closer to Earth at certain locations along its voyage. According to NASA, the precise distance between Earth and the moon can vary by approximately 26,222 miles (42,200 kilometers).
Supermoons occur when the moon is near or at its closest position to Earth (also known as its perigee) and appears full.
According to the United Kingdom’s National Space Centre, this is a “perigean full moon,” which is up to 30 percent brighter and 14 percent larger than full moons that occur at the farthest point from Earth.
Some argue that the term “supermoon” is overused because it can refer to full moons that do not occur at the exact closest point to Earth, and because they do not always appear significantly larger than a typical full moon to the human eye.
NASA explains that although “supermoon” is not an official astronomical term, “it’s used to describe a full Moon that comes within at least 90 percent of perigee.” And these lunar occurrences are not rare: Typically, three or four supermoons occur each year.
In actuality, the moon appears greatest in the sky when it is near the horizon, producing an optical illusion, according to Adam Block, an operations specialist at the Steward Observatory of the University of Arizona in Tucson. This phenomenon has no bearing on whether or not the moon is in supermoon territory.
Supermoons are neither uncommon nor visually distinctive, but they do have an effect on Earth. NASA observes that the physical proximity of the moon can cause increased tides in Earth’s oceans.
However, blue moons are more uncommon. While the term originally referred to an additional full moon occurring within the same tropical year — the interval between two equinoxes — it is now commonly used to describe two full moons occurring within the same calendar month.
Not all blue moons are supermoons, making the full moon on August 30 even more extraordinary. According to Espenak’s data, the next time two supermoons will occur in the same month is January 2037.
On January 31, 2018, for example, the last full moon of the month was not only a blue moon and a supermoon, but also a blood moon, or a total lunar eclipse. This created a genuinely extraordinary sky-watching experience. These phenomena occur when Earth’s shadow imparts a ruddy hue to the full moon.