Soho uses instraments that take reading at certain wavelengths that would pick up the difference chemical compounds in the Suns makeup. Metal objects would, in principal, would show up as weak signals as they would be reflecting the energy, not causing energy at those wavelengths.<br /><br />But not being a certified scientist, I could have read this off a bubble gum package.. <img border="0" title="" alt="[Smile]" src="images/icons/default/smile.gif" />