Sighting in Villejust, August 29, 2017

One evening, several witnesses noticed a section of green light beam in a cloudy sky. It would vanish and then come back a few moments later, always in the same spot. One of the witnesses took photographs. The sighting lasted about an hour, after which the witnesses went to bed. Looking at the pictures afterwards, the witness found white or blue "balls" on them. Only one account was collected, even though three people had been present.

The GEIPAN rated the case as having low strangeness and good consistency. The investigation concluded that the witnesses had seen the beam of the IPRAL laser at the SIRTA observatory, which belongs to the École Polytechnique, along with some stars. The green colour and the vertical orientation of the beam strongly suggested this laser, and the direction in which the witness was looking matched that of the observatory. When contacted, the observatory confirmed that the laser was operating at the time of the sighting. The "balls" seen on the photos were most likely stars, since their relative positions did not change between images taken several minutes apart. The double points of light may have been caused by camera movement during the exposure. The case was classified A.