A maelstrom is basically described as "a powerful whirlpool." While Khan's reference is relatively vague, it would appear to describe some sort of large swirling spatial anomaly found associated with the Antares system. On the other hand, as the original quotation spoke of the "Norway maelstrom," the allusion might have contained hyperbole on the part of Khan.
I'll chase him 'round the moons of speculation, 'round the Antares conjecture, and 'round perdition's supposition! -Angry Future Romulan 16:51, June 1, 2010 (UTC)