We present the high-resolution RGS X-ray spectrum of the stellar binary Cap
ella observed by the XMM-Newton satellite. A multi-thermal approach has fir
st been applied to fit the data and derive elemental abundances. Using the
latter, the emission measure distribution has been reconstructed using a Ch
ebychev polynomial fit. Its shape is found to display a sharp peak around 7
MK, consistent with previous EUVE and ASCA results. A smaller but signific
ant amount of emission measure is required around 1.8 MK in order to explai
n the O VII He-like triplet and the C VI Ly alpha line. We have applied the
temperature diagnostics of dielectronic recombination satellite lines to t
he He-like O VII triplet to constrain the cool plasma temperature, and have
obtained a lower limit consistent with the global reconstruction of the em
ission measure distribution. We have used line ratios from the forbidden, i
ntercombination, and resonance lines of the O VII triplet to derive an aver
age density for the cool coronal plasma (n(e) < 1 10(10) cm(-3)). implicati
ons for the coronal structure of Capella are discussed.