Space: Mystery from Way Out

One of those far-out fantasies that have long been a staple of science fiction is now a serious subject for scientific discussion—with the Russians taking it to new extremes. Two unusual radio "stars," wrote Astronomer Nikolai S. Kardashev in the Astronomical Journal of the Soviet Academy of Sciences, may be "supercivilizations" deep in space, calling attention to themselves by transmitting vast amounts of energy on peculiar, and therefore conspicuous, radio frequencies.

The two radio sources, catalogued as CTA-21 and CTA-102, were first detected by radio astronomers in 1960. Both are pinpoints in the sky, which means that they are either...

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