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(Photo by Leif Havik, copyright Project Hessdalen)

In the Hessdalen valley in Norway, strange lights have been reported floating through the sky for many years. Though interest in the phenomenon peaked in the 1980s, researchers have noted that written records of the luminous mystery go back to 1811. The lights come in a variety of colours (white, yellow and blue), sometimes remain still and sometimes flash, and can suddenly move at extreme speeds upwards into the atmosphere or down into the ground, or into one of the many lakes in the area. Their size has been estimated in some instances to be up to a few cubic metres across, and sometimes they have been observed for longer than ten minutes at a time.

For the past three decades, small groups of scientists have attempted to document and explain the ‘Hessdalen Lights’, though usually working with few resources and on a shoestring budget. Currently, a collaboration between Norwegian, Italian and French
researchers run 3 different stations at the location, and for a fortnight in September each year they set-up four temporary stations which are manned by up to 100 students and researchers. A couple of recent papers, presented at the 2012 European Geosciences Union General Assembly, suggest that these efforts are starting to make in-roads into the mystery.

In a paper titled “Different states of the transient luminous phenomena in Hessdalen valley, Norway”, researchers noted that the Hessdalen Lights observed so far can be categorised into six different ‘states’ – Doublet, Fireball, Plasma ray, Dust cloud, Flash and Invisible – and that the lights might be caused simply by ionized grains of dust:

The Hessdalen phenomena is not easy to detect, and approximately only 20 observations is done each year. The work done the last 14 years suggests that the phenomenon has different states, at least 6 detected so far. The states are so different that to see a coupling between them is difficult. New work done into dusty plasma physics suggest that the different phenomena’s may be of the same origin, since the ionized grains of dusty plasma can change states from weakly coupled (gaseous) to crystalline, altering shape/formation and leading to different phenomena. Optical spectrometry from 2007 suggested that the luminous phenomena consisted of burning air and dust from the valley. Work done by G.S Paiva and C.A Taft suggests that radon decay from closed mines may be the mechanism that ionizes dust and triggers this phenomena.

The paper notes, however, that further research has indicated that radon is not the energy source, and as such this element of the mystery remains unexplained.

Find out more about Project Hessdalen at the official website, which includes streaming video options if you’d like to keep an eye on the valley yourself.

(via The Examiner, thanks to Jack for the heads-up)