Your eyes may not be playing tricks on you: You might be staring at a supermoon!

A supermoon was defined by astrologer Richard Nolle in 1979 as "a new or full moon which occurs with the Moon within 90 per cent of its closest approach to Earth."

The moon does not orbit Earth in a perfect circle; it's more of an ellipse. So, during each of its roughly 27-day orbits, the moon will reach both a farthest distance and a closest distance to planet Earth.

When it's at the farthest point, apogee, it is also called a 'micromoon.' When it makes its closest approach to Earth, at perigee, the moon can appear up to 14 per cent larger in diametre.

While that size difference isn't easy to notice, what is more noticeable is that it can appear up to 30 per cent brighter than a micromoon.

Now, when that occurs and it coincides with the cycle of the moon we call a 'full moon,' that's is when we get a supermoon, and they can happen 2 to 5 times a year.

According to NASA, the Moon's overall average distance is the equivalent of about 30 Earths, lined up, side by side.