For nearly a decade, radio astronomers have recorded the telltale signals emitted by a streamer of hydrogen clouds off the far edge of the Milky Way. Most scientists have believed that the source of the signals is somewhere in the giant galaxy of some 200 billion stars that includes the sun and its planets. But a University of Maryland astronomer has a different idea. S. Christian Simonson III concludes in Astrophysical Journal Letters that the source is a separate pint-size galaxythe Milky Way's closest cosmic companion.
Most galaxies have been discovered by conventional optical...
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