Spoiler alert: Tonight's moon won't be blue in colour, it is just a name given to it due to it's time of occurrence!
A blue moon is called so because it is the second full moon in a calendar month. Every month has one full moon, but as the lunar cycle and our calendar is not in perfect sync, we get to see two full moons in one month at every three years' gap.
This year, July’s first full moon was on the 2nd and now the second full moon is today, July 31, Friday at IST 7 pm.
You will witness a similar phenomenon next in 2018.
When the phrase "once in a blue moon" was coined, it meant something so rare you'd be lucky (or unlucky) to see in your lifetime, according to NASA's National Space Science Data Center.
So, don't get confused next time you hear there is a blue moon waiting for you in the skies, as it's just a name. In fact, all the full moons have names.
Although many Native American Tribes gave distinct names to the full moon. The names given by the Algonquin tribes have passed the test of time as they still exist will a few variations. Aligned to the month they fall in, there names are:
January: the Wolf Moon, February: the Snow Moon, March: the Worm Moon, April: the Pink Moon, May: the Flower Moon, June: the Strawberry Moon, July: the Buck Moon, August: the Sturgeon Moon, September: the Harvest Moon, October: the Hunter’s Moon, November: the Beaver Moon, December: the Cold Moon. And finally the Blue moon.