Why in the News?

Researchers at the Indian Institute of Astrophysics (IIA) have successfully estimated the abundance of Helium in the Sun’s photosphere with precision for the first time.

About Helium in the Sun’s Photosphere:

• Helium is the second most abundant element in the Sun after Hydrogen and plays a key role in understanding solar composition, opacity, and energy transport.
• However, measuring its precise abundance in the Sun’s photosphere has been challenging due to the absence of observable Helium spectral lines in visible light.
• Traditionally, Helium abundance was estimated using indirect methods like extrapolating data from hotter stars, solar wind observations, and seismological studies of the Sun’s interior.
• These methods lacked direct photospheric observations, making the estimates less accurate.
• Accurate measurements of Helium are essential for modelling the Sun’s opacity and energy transport. This also has broader implications for understanding the composition of other stars.

Novel Method Recently Discovered:

• Researchers from the IIA introduced a novel method to directly estimate Helium abundance in the Sun’s photosphere.
• This technique uses spectral features from Magnesium (Mg) and Carbon (C), overcoming the challenge of no direct Helium spectral lines.
• Spectral lines from Mg, C, and hydrogenated molecules (MgH, CH, C2) were used to infer Helium abundance.
• Equivalent Width analyses and spectrum synthesis techniques helped model the behavior of these elements in varying Helium-to-Hydrogen ratios.
• The Helium-to-Hydrogen ratio in the Sun’s photosphere was found to be 0.1, consistent with previous studies. This confirms the validity of the new method.

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