Night sky – January 2018: Once in a Blue Moon

The full Moon on Jan 2 will be the perigee full Moon of 2018. Perigee is the point in an object’s elliptical orbit around the Earth where its distance to our planet is minimised. The Moon experiences perigee once per orbit but not always coinciding with full Moon. When it does, it produces a Moon which is appears slightly larger and brighter than those that proceed or follow it. The popular press uses the term Supermoon to describe such an event, a loose term originating from astrolog