A rare combination of celestial events will grace the night sky later this month. NASA says a supermoon lunar eclipse will take place September 27.
A supermoon occurs when a full moon coincides with the moon’s perigree — the point in the lunar orbit when it’s closest to the Earth — making it appear larger and brighter than normal. The supermoon at the end of this month is expected to be the closest one of 2015, a year that will see six supermoons in all.
A lunar eclipse, meanwhile, happens when the moon passes into alignment with the Earth and sun and briefly falls into Earth’s shadow. Space.com explains that during a total lunar eclipse, the moon often turns a reddish color when it’s hit by sunlight bent by the Earth’s atmosphere, resulting in a phenomenon called a “blood moon.”
It’s extremely unusual for a supermoon and total lunar eclipse to happen at the same time, as they will at the end of this month. NASA says it has happened only five times since 1900, most recently in 1982. There won’t be another one until 2033.