Today the Blue Moon is at its maximum.

Astronomy lovers will be able to admire the supermoon phenomenon, appearing on August 30 and reaching its maximum on the night of August 31, with the Moon at its largest and brightest state in 2023.

August is considered an astronomical "party" when there are two supermoons appearing in the sky. The Blue Moon, the second full moon in August, is only 357,344 km away from Earth. "In Vietnam, the supermoon can look about 7% bigger and brighter than a normal full moon," said Mr. Dang Vu Tuan Son, Chairman of the Vietnam Astronomy and Cosmology Association (VACA).

The supermoon took place at 1:35 a.m. on August 31 (8:35 a.m. Hanoi time). This is not a favorable time to watch the supermoon, because there is still sunlight. However, people in Vietnam can still admire the Moon in its almost full state. Mr. Son explained that the Moon's phase change is continuous because it does not "jump" into steps in its orbit and move continuously, so the full moon is a point, not a day. Therefore, on the evening of August 30 and 31, the Moon is basically the same fullness for observers in Vietnam.

This full moon is called a supermoon because it occurs at the exact moment when it is very close to perigee (the closest point in its orbit to Earth). On nights like this, the Moon appears slightly larger and brighter than usual.

Photo of the nearly full Moon. Photo: Dang Vu Tuan Son. — Photo of the nearly full Moon on August 30. Photo: *Dang Vu Tuan Son.*

Observing this event is exactly the same as for a normal full moon, that is, only needing a few clouds, enough to see the Moon. Observers also do not need to prepare any eye protection when observing. He added that it will not make a significant difference if the observing conditions are not favorable (when the sky is cloudy or the sky is too polluted).

According to the cultural beliefs of some Western countries, the second full moon in the same month is called a Blue Moon. The occurrence of two consecutive full moons in the same month, Mr. Son said, "is not too rare". According to the lunar cycle (the period between two consecutive full moons) is 29.53 days, while the solar month usually has 30 or 31 days, making it possible for two full moons to fall at both the beginning and the end of the solar month.

He emphasized that Blue Moon is actually just a cultural name, the Moon is never blue but is called the Blue Moon of the month. On average, there is one Blue Moon every year according to this calculation. However, to have two Blue Moons in the same year is quite rare. The last time a Blue Moon appeared in the same year was in January and March 2018 and the next will be in January and March 2037.

The 2023 supermoons will occur four times in a row in July, August, and September. On the last supermoon of 2023 on September 28, the Moon will fly 361,552 km from Earth. In 2024, there will be only two supermoons, on September 18 and October 18.

Nhu Quynh

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