R Coronae Borealis variable
RCB star atmospheres do however lack hydrogen by an abundance of 1 part per 1 , 000 down to 1 part per 1 , 000 , 000 relative to helium and other chemical elements , while the universal abundance of hydrogen is about 3 to 1 relative to helium . 
<triplet> helium <subj> chemical element <obj> instance of