  Recent improvements in the modeling of solar convection and line formation
led to downward revisions of the solar photospheric abundances of the lighter
elements, which in turn led to changes in the radiative opacity of the solar
interior and hence to conflicts with the solar convection zone depth as
inferred from helioseismic oscillation frequencies. An increase of the solar
Ne/O abundance to values as observed for nearby stars has been proposed as a
solution. Because of the absence of strong neon lines in the optical, neon
abundances are difficult to measure and the correct solar and stellar Ne/O
abundances are currently hotly debated. Based on X-ray spectra obtained with
XMM-Newton, we determine a reference value of Ne/O for the inactive, solar-like
star alpha Cen (primarily alpha Cen B, which is the dominant component in
X-rays), with three independent, line-based methods, using differential
emission measure reconstruction and an emission measure-independent method. Our
results indicate a value of approx. 0.28 for Ne/O in alpha Cen, approximately
twice the value measured for the Sun, but still below the average value
obtained for other stars. The low Ne/O abundance of the Sun is peculiar when
compared to alpha Cen and other stars; our results emphasize the necessity to
obtain more and accurate Ne/O abundance measurements of low activity stars.
