No. 13: Winter 1981
On March 5, 1979, a colossal burst of gamma rays swept through the solar system, triggering radiation detectors on nine different spacecraft. By comparing the times of arrival of the burst, the direction of the source was narrowed down to a "box" a couple of arc minutes across. Gamma-ray bursts have never before been correlated with visible sources, but this time the box contained the remnants of a supernova in the Large Magellanic Cloud, a satellite galaxy of our own Milky Way.
The anomaly that arises involves the immense distance of the supposed source and the strength of the burst when it reached the solar system. The power level of the supernova remnant gamma flash would have had to be about 1037 watts -- a stupendous figure. If the supernova remnant is a neutron star, as current theories suggest, the neutron star would have to be 10 to 100 times the size of the usual neutron stars.
(Anonymous; "Gamma-Ray Burst Comes from Outside the Galaxy," New Scientist, 87:776, 1980.)