This popular magazine article indicates that modern science (as of 2019) is uncertain whether iron stars will form, and their formation is dependent on how certain unknown physics constants work out a very long time into the future from now. Given the uncertainty over the physics, I'm happy to say "handwave it, it sounds fun for my DF game".
As regards extraction, then, it seems that a magical heat guard for a local tool is fine, and then the heat-guarded tool is pushed through the gate and retrieves a certain amount of meteoric iron in a potentially very hot and/or exotic state... which is then brought down to somewhat more conventional temperatures and physical states in the DF side of the portal.