The term simply comes from a rare event. This full moon is called a blue moon because we typically see three full moons in any given season. Another “blue moon” concept is the second full moon in a calendar month; that won’t happen again until January 31, 2018.
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This full moon can be considered a blue moon because it adheres to an older definition, according to EarthSky.org: The third of four full moons in one season. This year, however, it gets another name – Blue Moon. About every three years there is a 13th full moon. When this happens, the third full moon of the season is the blue moon.
If a blue moon is normally white, why is it called blue?
Below the moon and Mars you’ll see another prominent bright planet. Therefore, it’s inevitable that 7 out of 19 years will feature two full moons in one calendar month.
The dust and smoke particles that are released into the air during such events are usually the ideal size for blue light to pass through the atmosphere. “Stargazers will be treated to a celestial double whammy this weekend with a Blue Moon on Saturday and Mars opposition on Sunday”. That’s because Mars will shine bigger and brighter than any other time in the past two years as the Red Planet approaches the closest point in its orbit to Earth.
How often do blue moons occur?
Also Saturday, Saturn will be 8 degrees below the moon toward the horizon. But now they appear a little bit more often, because the definition of this astronomical event has changed over the past several decades.
In addition to the moon, you’ll get a cameo appearance from the planet Mars. Both will be visible in the eastern sky if the clouds can clear Saturday evening.
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The world is about to witness another rare celestial phenomenon after the transit of Mercury or the passing of the planet across the Sun that happened a few weeks ago.
