IIA study estimates abundance of helium in the sun

Researchers from the Indian Institute of Astrophysics (IIA) in a new study have been able to accurately estimate the abundance of helium in the sun for the first time. This finding could be a major step in assessing the opacity of the sun’s photosphere.

According to the Department of Science and Technology, astronomers have traditionally assumed the abundance of helium in the photosphere of sun-like stars to be one tenth of that of hydrogen by extrapolating from hotter stars, or from the outer atmosphere of the sun (solar corona, solar wind), or from seismology studies of the interior of the sun. “None of these methods are based on direct observations of the photosphere due to the absence of helium spectral lines,” it said,

It added that an accurate and reliable measurement of the abundance of the element helium in the photosphere of the sun remains a challenge for astronomers to this day.

“The abundance of various elements in our sun, or in any other star, is estimated from their absorption spectral lines. Since helium does not produce any observable spectral lines from the visible surface, or the photosphere of the sun, its abundance has usually been estimated through indirect means,” the department said.

Now, the IIA researchers have used a new method to estimate helium abundance in the sun. Using magnesium and carbon features in the observed high-resolution spectrum of the sun they have accurately calculated the abundance of the element.

“Using a novel and consistent technique, whereby the spectral lines of neutral magnesium and carbon atoms in conjunction with the lines from the hydrogenated molecules of these two elements are carefully modelled, we are able to constrain the relative abundance of helium in the sun’s photosphere now,” said Satyajeet Moharana, the first author of the published study and currently a PhD scholar at KASI, South Korea.

The other two authors of the study published in Astrophysical Journal are B.P. Hema and Gajendra Pandey.