[scentoni]

Only a small percentage of the plutonium's mass gets converted to energy during fission.

[jcims]

Indeed, this site says it's about 46g per megaton: http://www.jick.net/hr/skept/EMC2/node4.html

Still, 1kg has a field strength that's 5 orders of magnitude greater than a solar mass a billion light years away...10mg would be in the neighborhood.

If i didn't screw up the math, that's ridiculous.