Blue moons are not so recurrent but occur once every two to three years.
From time to time, a news item may appear about the appearance of a Blue Moon in the sky, and immediately confusion arises as to what exactly this term refers to. You might even wonder where this strange denomination originated from. Everything has an explanation and besides, there are upcoming dates to admire this beautiful astronomical phenomenon.
When it is said that there will be a Blue Moon, it does not refer exactly to the color of the Earth’s natural satellite, but to the periodicity with which it will appear on the calendar. While it is true that observing a bluish moon can be very tempting, the truth is that this phenomenon has little to do with the hue. In fact, the hue of our moon is a bit complex to explain, as it depends largely on the conditions of the Earth’s atmosphere and how the Sun’s rays interact with it, although that is another matter.
There are two types of blue moons
According to NASA, there are two types of blue moons: monthly and seasonal. And both are related to the periodicity of the occurrence of full moons in the calendar.
The monthly blue moon refers to the second full moon of the same month. Each month has its own full moon, so we have a lunar calendar in which there are 12 full moons per year. This was well known by the ancient cultures and also by the traditional North American peoples, who were in charge of giving a name to each full moon according to their cosmovision.
But as we know, the lunar cycle is shorter than the duration of a full month, so every so often in the same month, we can experience two full moons. This second full moon is called a Blue Moon.
The seasonal Blue Moon refers to the third full moon of an astronomical season of four full moons. In astronomy, the period between a solstice and an equinox, and vice versa, is called a ‘season.’ The year has four astronomical seasons, which we also call seasons, each divided into three months, so they must experience three full moons. But there are times when in the same astronomical season four full moons appear in the sky. When this happens, the third full moon is called a Blue Moon.
When will the next Blue Moon be?
Blue moons are not so recurrent but occur once every two to three years, which is why when they appear in the sky, observers of the satellite are filled with glory even though they know that a blue hue will not appear on the lunar surface.
The next monthly Blue Moon will be on August 31, 2023. While to admire seasonal blue moons we will have to wait until 2024, these are the dates for the next seasonal blue moons:
- August 19, 2024
- May 20, 2027
- August 24, 2029
- August 21, 2032
- May 22, 2035
Story originally published in Spanish in EcoosferaPodría interesarte