How rare is it? That depends on who you ask. But it's safe to say, Monday's full moon will be special.

 A super blue moon is a rare combination of two lunar events: a supermoon and a blue moon.

 A supermoon occurs when the moon is closest to Earth during a full moon, making it appear larger and brighter.

There are two types of blue moons: seasonal and monthly. The one on Monday is a seasonal blue moon.

 The alignment of a supermoon and a blue moon is a truly rare celestial event.

 According to NASA, the combination of a supermoon and a blue moon is a special occurrence.

Astronomers have different definitions for supermoons and blue moons, adding to the confusion.

Supermoons appear about 30% brighter and 14% larger than regular full moons.

 A seasonal blue moon is the third full moon in a season with four full moons.

The lunar cycles don't always align perfectly, making blue moons and supermoons, especially together, uncommon.