Concept in Definition ABC

In its movement of rotation around the Earth there is a moment each month in which the Moon is at the distance closest possible to the center of the Earth. That moment is known as perigee. When the lunar perigee coincides with the full Moon phase, the phenomenon known as Supermoon occurs, in which the Moon appears even larger.

The Supermoon is an optical phenomenon, since an observer perceives it with a larger than real size. Consequently, the appearance of a Supermoon has two reasons: one physical and the other related to the visual perception. From the point of view of movement, the Moon rotates on itself and at the same time around the Earth in a displacement It has an elliptical orbit shape. However, the center of this orbit is not equal to the center of the Earth and, consequently, the distance from the Moon and the Earth is not constant. This aspect of the lunar movement determines our perception optics at the time when the perigee and the full moon coincide.

Supermoons occur periodically, since they occur between three and five times a year (in a year there are between 12 and 13 times when there is a full Moon).

The visual perception of the supermoon

The brightness of the moon is significantly higher when there is a supermoon, since the perception of brightness changes when the Moon is at a distance less than usual. This optical effect conveys a sensation peculiar, because it seems as if the Moon could almost touch. Astronomers have indicated that this optical phenomenon is most intense when the Moon is observed over the horizon. In this way, the ideal time to observe the supermoon would be a little before dawn, when it is closest to the horizon line.

The Moon in language

The Moon holds a fascination for lovers, poets and astronomers. The influence of the Moon also appears in the language. Lovers who get married celebrate their union on a honeymoon. When someone experiences a moment of fulfillment and happiness he can say that he has touched the moon with his fingers. If someone is not focused on what they are doing, it is because they are on the moon. Weird people are sometimes called lunatics. This influence of the moon on the language everyday life has an explanation: our satelite natural transmits ideas and feelings which are then translated into words.

Photos: iStock - jvazquezm / Songquan Deng