Blue Moon, a rare astronomical phenomenon wherein a second full moon appers in a particular month, can be witnessed across several parts of the world on Friday.

The American continent will witness this lunar event for the first time since August 2012, as a full moon rises for the second time in July. According to experts the blue moon -- which is not necessarily blue in colour -- will have risen just after sunset on Thursday, but will be visible in all its splendour only at 6.43 am.

The rare occurrence, which explains the etymology of the phrase "once in a blue moon", will happen next in 2018. Though the blue moon wll not have a bluish shade -- being just the second full moon in a calendar month -- there have been instances when the moon did look blue, but that was only due to smoke and dust.

The most recent truly blue moon was witnessed in September 1950 in Edinburgh, Scotland. The researchers had found that the bluish hue in Scotland was caused by the smoke and ash from a forest fire in Canada, according to CNN.

According to, the term Blue Moon was coined in 1946 in an article published by Sky & Telescope, who defined a blue Moon as the second full moon in a calender month. Today, this definition is widely accepted.

By this definition, the next Blue Moon will take place roughly 2.7 years later, that is on 31 January, 2018.

Chicago's Adler Planetarium Astronomer Larry Ciupik told NBC that despite the fact that the Blue Moon on 31 July does not look any different from a usual full moon, there is a general mystery around the celestial occurrence with people claiming to have seen faces in the orb or experience strange events during the lunar event.

"It's also a kind of romantic thing," Ciupik added.

The Blue Moon 2015 will occur at exactly 6:43 am EDT (1043 GMT). Those who can't get out of their homes early can also watch live streaming of the Blue Moon 2015 from the comfort of their homes as Slooh Space Camera will live-stream the event.

The online live streaming from Canary Islands will be available from 8:30 pm EDT.  Online live streams also will be available on Periscope. [Watch Here]

Also watch for free online on Youtube.