Did you know that tonight is a blue moon? Neither did we. Until, Josh, our resident astrology expert filled us in on all-things-blue-moon.

Defined as the second full moon in a single month, those looking up tonight will be treated to a view of what’s commonly known as a blue moon. But blue moons of this sort aren’t really blue and don’t actually have anything to do with color. (Certain natural occurrences, like volcanic eruptions or wildfires can cause the moon to appear red, orange, or blue, as pictured above.)

Though the expression, “once in a blue moon” is used to describe extremely rare events, blue moons aren’t all that unusual. The monthly calendar was built on the lunar cycle (29.5 days), so there is usually only one full moon per month. But once every 2 1/2 years or so, those extra half days add up to two full moons in a month. It is, however, relatively rare for a blue moon to fall on New Year’s Eve (this won’t happen again until 2028). And it is even rarer for it to fall on New Year’s Eve of a new decade.

This year has been designated International Year of Astronomy , as the world celebrated the 400th anniversary of Galileo’s use of a telescope to study the skies. Tonight’s blue moon is a perfect conclusion to the year’s astronomical festivities.

People tend to be more emotionally expressive during a full moon because of the change in the electromagnetic energy that affects them mentally and neurologically. Be prepared to see some drastic changes to your energy field and your choices.