Direct observations of the supposedly universal primordial deuterium abundance imply a relatively large baryon density \Omega _ { B } = ( 0.019 - 0.030 ) h ^ { -2 } ( 95 % C.L . ) .
On the other hand , concordance between the previously accepted ^ { 4 } He and ^ { 7 } Li abundances and standard Big Bang Nucleosynthesis requires the thrice smaller value \Omega _ { B } = ( 0.005 - 0.010 ) h ^ { -2 } ( 95 % C.L . ) .
For each \Omega _ { B } , we use X-ray and Sunyaev-Zeldovich observations of the baryon fraction f _ { B } in rich clusters of galaxies , in order to obtain limits on the total mass density \Omega _ { cl } in clusters of galaxies .
The higher- \Omega _ { B } values are consistent with clusters being a fair sample of the Universe , and then imply \Omega _ { m } = ( 0.3 - 0.9 ) , a medium or critical density Universe .
Said otherwise , the observed limits f _ { B } > 0.1 ,~ { } \Omega _ { m } > 0.3 imply \Omega _ { B } > 0.03 .
If the newer ^ { 4 } He abundance observations are accepted , this is consistent with standard BBN .