Recently found super dense planets about the size of the Earth but denser than iron could the remnants of Neptune like ice giants that migrated too close to their home stars. Theories about planet formation do not adequately explain these super dense planets..

 

http://www.scientificamerican.com/article.cfm?id=puzzling-super-dense-space-objects-could-be-a-new-type-of-planet&WT.mc_id=SA_DD_20130314

That is really cool. I guess we found supermans home planet

Edited March 18, 201312 yr by The Peon

Reminds me a science fiction novel where the protagonists were mining the surface of a previously Jupiter class planet in orbit around a star that had gone super nova, the outer layers had been blown away and super heavy elements had been deposited on the surface of the remnant of the planet...