A blue supermoon is a rare astronomical event that combines two distinct phenomena:

• Supermoon: This occurs when a full moon coincides with the Moon being at or near its closest point to Earth in its elliptical orbit, called perigee. At this time, the Moon appears up to about 14% larger and brighter than usual

• Blue Moon: This term traditionally refers to either the second full moon occurring within a single calendar month (monthly blue moon) or the third full moon in a season that has four full moons instead of the usual three (seasonal blue moon). Despite the name, the Moon does not actually appear blue in color during these events

When these two events happen simultaneously-a full moon that is both a supermoon and a blue moon-it is called a blue supermoon. This is quite rare, occurring roughly once every decade or so

. To summarize:

• A blue supermoon is a full moon that is both a supermoon (closest to Earth, appearing larger and brighter) and a blue moon (the second full moon in a month or the third full moon in a four-full-moon season).
• The Moon does not literally turn blue during this event.
• Blue supermoons are uncommon, with intervals averaging about 10 years between occurrences