A star seems to have been dimming for years, possibly because of a cloud of material obscuring it from view.

Benjamin Montet at the California Institute of Technology and Joshua Simon at the Carnegie Observatories, both in Pasadena, used instruments on NASA's Kepler spacecraft to study a star in the constellation Cygnus called KIC 8462852, which is brighter and larger than the Sun. Four years of observations revealed that the star dimmed slowly at first, by around 0.9% in total, then faded more rapidly by 2% in only six months. A few other stars nearby also became dimmer, but not to the same extent.

The authors speculate that the star's dimming could be explained by the collision or break-up of a planet or comets in the star's system, creating a cloud of spreading debris.

Astrophys. J. Lett. in the press; preprint at https://arxiv.org/abs/1608.01316 (2016)