A telescope has detected a mysterious millisecond burst of radio waves that seems to be coming from outside the Milky Way.

Laura Spitler at the Max Planck Institute for Radio Astronomy in Bonn, Germany, and her colleagues found the burst using the Arecibo radio telescope in Puerto Rico. The Parkes telescope in New South Wales, Australia, had previously picked up similar pulses — matching in brightness and duration — but a lack of comparable findings from other instruments at the time led astronomers to speculate that the signals were caused by instrument error or by radio interference from human sources.

Possible origins of the pulses include evaporating black holes, mergers of neutron stars or flares from magnetically active stars, say the authors.

Astrophys. J. 790, 101–109 (2014)