Friday's night sky to feature rare 2nd blue moon of year

Friday night will feature the second blue moon of 2018, the first time that a blue moon has fallen in both January and March since 1999.

A blue moon is the second full moon in a calendar month and typically only occurs once every two or three years. The length of time between occurrences is how the term "once in a blue moon" was derived.

However, this weekend will mark the first time that two blue moons occurred so close to each other in nearly 20 years.

"The last time we've seen two blue moons within three months was in 1999," AccuWeather Astronomy Blogger Dave Samuhel said.

The unusually close proximity of the two blue moons is due to the combination of the short month of February and the period of time between full moons.

Since February is comprised of only 28 days and a full moon occurs approximately once every 29.5 days, some years the entire month of February can pass in between full moons.

This was the case this year with a full moon falling on Jan. 31, 2018, then again on March 1, 2018. As a result, both January and March have two full moons, the second of which taking the nickname of a blue moon.

This happens about once every 19 years with 2037 being the next time that there is a blue moon in both January and March.

Contrary to its name, Friday night's full moon will not appear blue.

"The term ‘blue moon' actually has nothing to do with the color of the moon," Samuhel said. "Blue moons are usually the same gray and white color of a regular [full] moon."

However, the moon may appear red or orange in color when it is near the horizon, similar to how the sky turns red and orange around sunrise and sunset.

People hoping to see this phenomenon should look to the east just as the moon rises or to the west just as the moon is about to set.

Friday night's blue moon will be different from the one at the end of January that was also a supermoon and occurred during a total lunar eclipse.

If the weather does not cooperate for onlookers on Friday night, people can look for the moon again on Saturday night as the moon will still appear to be full.

Sunday night will also be a good chance for stargazers to look for the nearly full moon as it will be sitting in the sky right next to Jupiter, making the planet easy to spot.

Friday night's blue moon will be the last time that there are two full moons in a calendar month until October 2020 when a blue moon will occur on Halloween.

Questions or comments? Email Brian Lada at Brian.Lada@accuweather.com and be sure to follow him on Twitter!
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