The most recent measurements of the temperature and low-multipole polarization anisotropies of the Cosmic Microwave Background ( CMB ) from the Planck satellite , when combined with galaxy clustering data from the Baryon Oscillation Spectroscopic Survey ( BOSS ) in the form of the full shape of the power spectrum , and with Baryon Acoustic Oscillation measurements , provide a 95 \% confidence level ( CL ) upper bound on the sum of the three active neutrinos \sum m _ { \nu } < 0.183 eV , among the tightest neutrino mass bounds in the literature , to date , when the same datasets are taken into account .
This very same data combination is able to set , at \sim 70 \% CL , an upper limit on \sum m _ { \nu } of 0.0968 eV , a value that approximately corresponds to the minimal mass expected in the inverted neutrino mass hierarchy scenario .
If high-multipole polarization data from Planck is also considered , the 95 \% CL upper bound is tightened to \sum m _ { \nu } < 0.176 eV .
Further improvements are obtained by considering recent measurements of the Hubble parameter .
These limits are obtained assuming a specific non-degenerate neutrino mass spectrum ; they slightly worsen when considering other degenerate neutrino mass schemes .
Current cosmological data , therefore , start to be mildly sensitive to the neutrino mass ordering .
Low-redshift quantities , such as the Hubble constant or the reionization optical depth , play a very important role when setting the neutrino mass constraints .
We also comment on the eventual shifts in the cosmological bounds on \sum m _ { \nu } when possible variations in the former two quantities are addressed .