Visible in Mexico, Turkey and China, the supermoon seen on the night of August 19-20 is the first in a series of four this year. In September, it will coincide with a partial lunar eclipse.

The term "supermoon" is not an astronomical term and has no precise definition. It was coined in 1979 by Richard Nolle, an astrologer, and has since been used regularly in the English-language press to designate the moment when the Moon's perigee passage (its closest point of approach to the Earth) coincides with the full moon.