If you want to see the blue moon, you should hurry up and witness it this weekend during Easter. This astronomical event, also called the Sap moon, will be the last of its kind until 2020, during the Halloween night. Therefore, if you miss the chance during this weekend, you’ll have to wait for two and a half years to do it.
What is a blue moon?
A blue moon is actually the second full moon of a month. On average, full moons occur once every 29 days, so at least one such event occurs every month. Given the average period of 29 days between the events, it can happen that two full moons occur during the same month. However, this only takes place once every three years.
Therefore, the term of blue moon doesn’t come from its color. They look just like a regular moon, so their color remains that recognizable bright grey. However, on some really special occasions, the moon might really turn blue. After volcanic eruptions, the ash particles in the atmosphere allow blue light to pass through the clouds and change the color of the moon.
Two blue moons and two definitions
There are actually two types of blue moons, and they have two different definitions. There is the seasonal one, which represents the third full moon of an astronomical season. These are the same as our seasons, only they start at a different date. The astronomical spring and autumn start with the equinox, while the astronomical summer and winter start with the solstice.
The monthly one represents the second full moon of a month. In 2018, March was such a month, as well as January, when we could witness a blue moon during a lunar eclipse. If you want to watch this month’s astronomical event, you can do it on March 31st, during early morning.
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