Just before daybreak on May 5th, experienced sky watchers in Northern Ireland were surprised by a sudden apparition of noctilucent clouds (NLCs). "I was outdoors looking for eta Aquarid meteors when I spotted an eerie glow between my neigbour's houses." reports Martin McKenna of Maghera, Co. Derry. "The strong blue color was unmistakable--it was an NLC."
Noctilucent clouds are mainly a summertime phenomenon and it is very unusual for them to appear so early in May. "In my long years of observing NLCs, this is the earliest I have ever seen them."
These sightings only add to the mystery of NLCs. High-latitude "night-shining clouds" were first reported in the 19th century after the eruption of super-volcano Krakatoa. At the time, the clouds were widely thought to be associated with the volcano. Long after the ash settled, however, NLCs persisted. In recent years they have intensified and spread with sightings as far south as Utah and Colorado. What causes the phenomenon? A NASA spacecraft named AIM is orbiting Earth on a mission to find out.
Readers, browse our 2007 NLC Photo Gallery for observing tips.