Sighting in Saint-Michel-sur-Orge, August 10, 2015

Between 1 and 2 a.m., on the night of Sunday to Monday, two people noticed a coloured light in the sky that intrigued them. One of the two witnesses took photographs. Only one account was collected by GEIPAN. The point of light moved slowly for about an hour. The witness saw the phenomenon again on the following days, sometimes looking different and showing fewer colours.

Investigators noted that such a long observation of a slowly moving point of light suggested a celestial body. At the time, the star Arcturus was at an azimuth of 283° and an elevation of 13°, fairly close to the horizon. The witness had given an azimuth of 282° and an estimated elevation of 15°, at the intersection of the N104 and the A10, so the two directions matched. The weather that evening was unsettled, with changes in pressure and wind. Stars twinkle strongly at low elevation, especially in a disturbed atmosphere, and a slow multicoloured flicker is often seen through binoculars on stars or planets near the horizon. The witness did not mention any star in their field of view, although Arcturus must have been visible in that direction. The photographs were blurred by camera movement and too dim to add much information.

GEIPAN classified the case as A: the observation of the star Arcturus.