How the Iron in Our Sun is Key to Energy Transmission

After working with temperatures as hot as the interior of the sun, researchers have managed to find out iron's role in inhibiting energy transmission from the sun to the near edge of its radiative band.

Scientists have modeled the reactions that occur within the sun before. Yet a gap between this model and observations appeared in 2000 when analysis of spectra emerging from the sun forced scientists to lower their estimates of energy-absorbing elements such as oxygen, nitrogen and carbon by 30 to 50 percent. These decreased abundances meant that the model then predicted that energy would arrive at the sun's radiative edge more readily than before. This, in turn, created a discrepancy between the sun's theoretical structure and its measured structure. In other words, something didn't add up.

"The inside of a star is one of the most mysterious places in the universe," said Jim Bailey, one of the researchers, in a news release. "It's too opaque for distant instruments to see inside and analyze reactions within it, and too hot to send a probe into it." He continues by saying, "Fortunately, in our Z experiments, we can create temperature and density conditions nearly the same as the region inside the sun that affects the discrepancy most-the edge of the zone where radiative energy transport dominates-in a sample that's big enough, lasts long enough, and is uniform enough to test."

In order to get to the bottom of this problem, the researchers needed a way to balance the decreased resistance to radiation transport caused by the lowered amounts of elements. That's why they conducted experiments spanning a 10-year period. In the end, they discovered that the widely used astrophysical estimate of the wavelength-dependent opacity of iron should be increased between 30 to 400 percent. This difference didn't represent a large uncertainty, but rather how much iron's opacity varied with the wavelength of the radiation.

The findings reveal a bit more about the processes that occur within the interior of our sun. This, in turn, can tell researchers about other stars in other solar systems.

The findings are published in the journal Nature.

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