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Blue moon - Wikipedia

en.wikipedia.org/wiki/Blue_moon

A blue moon is an additional full moon that appears in a subdivision of a year: either the third of ... In modern use, when 13 full moons occur in a year, usually one calendar month has two full moo...

Once in a Blue Moon - Obliquity

www.obliquity.com/astro/bluemoon.html

Once in a Blue Moon: what does it mean and how often does it happen?

When is the next Blue Moon? | Astronomy Essentials | EarthSky

earthsky.org/astronomy-essentials/when-is-the-next-blue-moon

Jan 31, 2017 ... But folklore has defined 2 other Blue Moons, too, which are more commonly ... How often does a "blue moon" occur that is one by both of the ...

Blue Moons Explained (Infographic) - Space.com

www.space.com/16776-blue-moon-explained-infographic.html

Aug 31, 2012 ... Traditionally, a Blue Moon is an extra full moon in the span of three months. ... a Blue Moon is an extra new moon that occurs due to a quirk of the calendar. ... The second full moon is also often called a Blue Moon, but this is ...

Blue Moons: myths, facts, history, and dates - Infoplease

www.infoplease.com/spot/bluemoon1.html

How Often Does a Blue Moon Occur? Over the next 20 years there will be about 15 blue moons, with an almost equal number of both types of blue moons ...

How often does a blue moon occur? | Reference.com

www.reference.com/science/blue-moon-occur-2c0e817449138e0e

A blue moon is the second full moon in a calendar month and occurs roughly once every 2.7 years, according to Space.com. The term is used in the English ...

What Is a Blue Moon? - Time and Date

www.timeanddate.com/astronomy/moon/blue-moon.html

There are two definitions of a Blue Moon in astronomy; both are a type of Full Moon. ... Astronomical Blue Moons happen either once every 2 to 3 years or so, ...

What is a blue moon?? Everyday Mysteries: Fun Science Facts from ...

www.loc.gov/rr/scitech/mysteries/bluemoon.html

Have you ever heard the expression “once in a blue moon?” It means 'not very often,' or 'very rarely,' but exactly how often does a so-called blue moon occur?

Blue Moon Calendar - Moongiant

www.moongiant.com/Blue_Moon_Calendar.php

A Full Moon occurs roughly every 29.5 days and on the rare occasions when the Full Moon falls at the very beginning of a ... According to this definition the next Blue Moon will occur on January 31, 2018. ... This is a very rare event but it does happen. ... Neither of these definitions or the term Dark Moon is used very often.

Blue Moons - NASA

nssdc.gsfc.nasa.gov/planetary/lunar/blue_moon.html

Nov 8, 2016 ... A "Blue Moon" is the name given to the second full moon in a ... A double Blue Moon most commonly occurs in January/March but is also ...