title: A higher-than-predicted measurement of iron opacity at solar interior temperatures.
abstract: Nearly a century ago it was recognized that radiation absorption by stellar matter controls the internal temperature profiles within stars. Laboratory opacity measurements, however, have never been performed at stellar interior conditions, introducing uncertainties in stellar models. A particular problem arose when refined photosphere spectral analysis led to reductions of 30-50 per cent in the inferred amounts of carbon, nitrogen and oxygen in the Sun. Standard solar models using the revised element abundances disagree with helioseismic observations that determine the internal solar structure using acoustic oscillations. This could be resolved if the true mean opacity for the solar interior matter were roughly 15 per cent higher than predicted, because increased opacity compensates for the decreased element abundances. Iron accounts for a quarter of the total opacity at the solar radiation/convection zone boundary. Here we report measurements of wavelength-resolved iron opacity at electron temperatures of 1.9-2.3 million kelvin and electron densities of (0.7-4.0) × 10(22) per cubic centimetre, conditions very similar to those in the solar region that affects the discrepancy the most: the radiation/convection zone boundary. The measured wavelength-dependent opacity is 30-400 per cent higher than predicted. This represents roughly half the change in the mean opacity needed to resolve the solar discrepancy, even though iron is only one of many elements that contribute to opacity.
authors.affiliation: Sandia National Laboratories, 1515 Eubank SE, Albuquerque, New Mexico 87185-1196, USA.
authors.forename: J E
authors.initials: JE
authors.lastname: Bailey
authors.affiliation: Sandia National Laboratories, 1515 Eubank SE, Albuquerque, New Mexico 87185-1196, USA.
authors.forename: T
authors.initials: T
authors.lastname: Nagayama
authors.affiliation: Sandia National Laboratories, 1515 Eubank SE, Albuquerque, New Mexico 87185-1196, USA.
authors.forename: G P
authors.initials: GP
authors.lastname: Loisel
authors.affiliation: Sandia National Laboratories, 1515 Eubank SE, Albuquerque, New Mexico 87185-1196, USA.
authors.forename: G A
authors.initials: GA
authors.lastname: Rochau
authors.affiliation: Commissariat à l'Énergie Atomique (CEA) et aux Énergies Alternatives, F-91297 Arpajon, France.
authors.forename: C
authors.initials: C
authors.lastname: Blancard
authors.affiliation: Los Alamos National Laboratory, Bikini Atoll Road, Los Alamos, New Mexico 87545, USA.
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authors.affiliation: Commissariat à l'Énergie Atomique (CEA) et aux Énergies Alternatives, F-91297 Arpajon, France.
authors.forename: Ph
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authors.lastname: Cosse
authors.affiliation: Commissariat à l'Énergie Atomique (CEA) et aux Énergies Alternatives, F-91297 Arpajon, France.
authors.forename: G
authors.initials: G
authors.lastname: Faussurier
authors.affiliation: Los Alamos National Laboratory, Bikini Atoll Road, Los Alamos, New Mexico 87545, USA.
authors.forename: C J
authors.initials: CJ
authors.lastname: Fontes
authors.affiliation: Commissariat à l'Énergie Atomique (CEA) et aux Énergies Alternatives, F-91297 Arpajon, France.
authors.forename: F
authors.initials: F
authors.lastname: Gilleron
authors.affiliation: Prism Computational Sciences, 455 Science Drive, Suite 140, Madison, Wisconsin 53711, USA.
authors.forename: I
authors.initials: I
authors.lastname: Golovkin
authors.affiliation: Sandia National Laboratories, 1515 Eubank SE, Albuquerque, New Mexico 87185-1196, USA.
authors.forename: S B
authors.initials: SB
authors.lastname: Hansen
authors.affiliation: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550-9234, USA.
authors.forename: C A
authors.initials: CA
authors.lastname: Iglesias
authors.affiliation: Los Alamos National Laboratory, Bikini Atoll Road, Los Alamos, New Mexico 87545, USA.
authors.forename: D P
authors.initials: DP
authors.lastname: Kilcrease
authors.affiliation: Prism Computational Sciences, 455 Science Drive, Suite 140, Madison, Wisconsin 53711, USA.
authors.forename: J J
authors.initials: JJ
authors.lastname: MacFarlane
authors.affiliation: University of Nevada, 1664 North Virginia Street, Reno, Nevada 89557, USA.
authors.forename: R C
authors.initials: RC
authors.lastname: Mancini
authors.affiliation: Ohio State University, 140 West 18th Avenue, Columbus, Ohio 43210, USA.
authors.forename: S N
authors.initials: SN
authors.lastname: Nahar
authors.affiliation: Ohio State University, 140 West 18th Avenue, Columbus, Ohio 43210, USA.
authors.forename: C
authors.initials: C
authors.lastname: Orban
authors.affiliation: Commissariat à l'Énergie Atomique (CEA) et aux Énergies Alternatives, F-91297 Arpajon, France.
authors.forename: J-C
authors.initials: JC
authors.lastname: Pain
authors.affiliation: Ohio State University, 140 West 18th Avenue, Columbus, Ohio 43210, USA.
authors.forename: A K
authors.initials: AK
authors.lastname: Pradhan
authors.affiliation: Los Alamos National Laboratory, Bikini Atoll Road, Los Alamos, New Mexico 87545, USA.
authors.forename: M
authors.initials: M
authors.lastname: Sherrill
authors.affiliation: Lawrence Livermore National Laboratory, 7000 East Avenue, Livermore, California 94550-9234, USA.
authors.forename: B G
authors.initials: BG
authors.lastname: Wilson