Find out the latest thinking about our universe.
-
MargaritaMc
- Look to the Evenstar
- Posts: 1836
- Joined: Wed Jan 09, 2013 10:14 pm
- Location: 28°16'7"N 16°36'20"W
Post
by MargaritaMc » Wed Dec 31, 2014 12:55 pm
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
Last edited by
bystander on Thu Jan 08, 2015 3:57 pm, edited 1 time in total.
Reason: Split from JPL: Sun Sizzles in High-Energy X-Rays
"In those rare moments of total quiet with a dark sky, I again feel the awe that struck me as a child. The feeling is utterly overwhelming as my mind races out across the stars. I feel peaceful and serene."
— Dr Debra M. Elmegreen, Fellow of the AAAS
-
bystander
- Apathetic Retiree
- Posts: 21588
- Joined: Mon Aug 28, 2006 2:06 pm
- Location: Oklahoma
Post
by bystander » Wed Jan 07, 2015 6:43 pm
'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
Know the quiet place within your heart and touch the rainbow of possibility; be
alive to the gentle breeze of communication, and please stop being such a jerk. — Garrison Keillor