Q&A: X-ray Astronomy

Q:
I quote from http://chandra.harvard.edu/photo/2000/0170/index.html: "The Roman numerals refer to how many electrons have been stripped from the atoms. e.g. OVIII is an ion that has lost 7 electrons from its atomic shell, NeX has lost 9 electrons, etc." This does not make sense. Do you mean OVIII has lost eight electrons and NeX has lost ten?

A:
Blame it on the Romans for not inventing zero. The neutral atoms, with zero electrons removed are labeled with I. For example HI for a neutral hydrogen atom, OI for a neutral oxygen atom, etc.