Nature: Iron opacity of the Sun higher than predicted

[MargaritaMc]

I thought I'd post this here, rather on a new thread, although it's only tangentially related. But it interested me.

Nature letters: A higher-than-predicted measurement of iron opacity at solar interior temperatures
J. E. Bailey, T. Nagayama et al
Nature 517, 56–59 (01 January 2015) doi:10.1038/nature14048
Received 17 September 2014 Accepted 03 November 2014 Published online 31 December 2014

Editor's summary
Internal temperature profiles of the Sun and other stars are controlled in large part by the rate at which radiation is absorbed by stellar matter. Until now it has not been possible to determine the opacity of matter in star-like conditions in the laboratory, but James Bailey et al. have now achieved that feat using the Sandia National Laboratories' Z facility, the world's most powerful X-ray generator. The experiments reveal a wavelength-resolved iron opacity that is 30 to 400 times greater than predicted in conditions very similar to those at the radiation/convection zone boundary in the Sun. Previous measurements of stellar interiors have been based on observations of surface waves, and there were serious discrepancies between theoretical predictions and observations. The new measurements account for about half of adjustment in opacity figures required to restore agreement between standard solar models and observations.

Although the actual letter is behind a £22 paywall, the authors' abstract at this link is both informative and concise.

M

[bystander]

'Iron Sun' is not a Rock Band, but a Key to how Stars Transmit Energy
Sandia National Laboratories | DOE | NNSA | 2015 Jan 06

Working at temperatures matching the interior of the sun, researchers at Sandia National Laboratories’ Z machine have been able to determine experimentally, for the first time in history, iron’s role in inhibiting energy transmission from the center of the sun to near the edge of its radiative band — the section of the solar interior between the sun’s core and outer convection zone.

Because that role is much greater than formerly surmised, the new, experimentally derived amount of iron’s opacity — essentially, its capacity for hindering the transport of radiative energy originating in nuclear fusion reactions deep in the sun’s interior — helps close a theoretical gap in the Standard Solar Model, widely used by astrophysicists as a foundation to model the behavior of stars.

“Our data, when inserted into the theoretical model, bring its predictions more closely into alignment with physical observations,” said Sandia lead investigator Jim Bailey. His team’s work appeared Jan. 1 in the journal Nature. ...

A higher-than-predicted measurement of iron opacity at solar interior temperatures - J. E. Bailey et al

• Nature 517(7532) 56 (2015 Jan 01) DOI: 10.1038/nature14048