Rare 'Supermoon Blue Moon' begins Monday; 1st of 4 upcoming supermoons

Aug. 17 (UPI) -- Sky gazers across the United States and the rest of the world have a treat in store next week when a rare "Supermoon Blue Moon" will come into view, one of four on tap in the coming months.

The upcoming supermoon event begins at 2:26 p.m. EDT on Monday and will last for three days, according to NASA.

A supermoon is defined as a new or full Moon that occurs when the Moon is within 90% of its closest approach to Earth. Full supermoons tend to be spectacular sights because they are the biggest and brightest full Moons of the year.

Next week's Supermoon Blue Moon event will be the first of four consecutive supermoons during the remainder of this year, along with upcoming full moons on Sept. 17, Oct. 17 and Nov. 15.

The Moon will be closest to Earth during the "Hunter's Moon" supermoon event on Oct. 17.

Despite its name, Monday's supermoon will not actually appear to be blue. Rather, it is called a "Blue Moon" because since the 1940s the term has been officially used to describe the second full moon in a month that has two such events.