Researchers at the Indian Institute of Astrophysics (IIA), an autonomous institute of the Department of Science and Technology (DST), have found a new method to accurately calculate the abundance of helium in the Sun.

This study was published in ‘Astrophysical Journal’.

It could be a major step in assessing the opacity of the Sun’s photosphere.

Significance of this method

• Helium is the second most abundant element in the Sun after Hydrogen.

• Earlier, astronomers 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.

• An accurate and reliable measurement of the abundance of the element helium in the photosphere of the Sun was a major challenge for astronomers. 

• 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 researchers at the Indian Institute of Astrophysics (IIA) used magnesium and carbon features in the observed high-resolution spectrum of the Sun to accurately calculate the abundance of helium in the Sun.

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