CAMBRIDGE, Oct. 15 -- A radio shape once mistaken for a pulsar appears to be the afterglow of a black hole's old outburst, revived by a collision between two galaxy clusters hidden behind the Milky Way.

The object, catalogued as VLSS J0318.9+5755 and nicknamed the Treble Clef for its resemblance to the musical symbol, was described by a team led by Andrea Botteon of Italy's National Institute for Astrophysics, NASA's Chandra X-ray Observatory said on Wednesday. The resemblance is pareidolia, NASA noted, with no scientific link to music.

The source sits almost directly behind the Milky Way's plane, where stars, gas and dust block much of the view, and at such low Galactic latitude it was first classified as a pulsar candidate. Chandra an...