A recent article [http://www.newscientist.com/article/mg21328465.400-did-star-cluster-death-ray…] suggests that a blast of radiation from a nearby star cluster, specifically gamma rays, could be the cause of mass extinctions.

Gamma-Ray Bursts (GRBs) occur when a massive star explodes (supernova) or when 2 neutron stars merge. If a GRB occurred in a star cluster we can trace its position and speed to deduce whether it coincides with past extinction events [the European Space Agency’s Gaia star-mapper (2013) will determine the position and speed of star clusters].

The author calculated that at least 1 GRB has occurred within striking distance of the Earth in the last billion years.

Paper: arxiv.org/abs/1112.1792