A New Method to Estimate Helium Abundance in the Sun

Syllabus: GS3/ Science and Technology

Context

• A recent study by the Indian Institute of Astrophysics (IIA) has accurately estimated the abundance of helium in the Sun’s photosphere. 

Background

• Helium is the second most abundant element in the Sun after hydrogen, playing a vital role in its structure and energy dynamics. 
• To accurately measure its abundance in the Sun’s photosphere has been a long-standing challenge due to the lack of helium spectral lines in the visible range.
• Traditional methods relied on indirect data from hotter stars, the solar corona and wind, and helioseismology (study of the Sun’s internal oscillations).

The new methodology

• Researchers analyzed high-resolution solar spectra to study both atomic and molecular spectral lines. 
• They focused on neutral magnesium (Mg) and magnesium hydride (MgH), as well as neutral carbon (C) and its molecular forms CH and C₂.

How does the method work? 

• The spectral lines of both atomic and molecular forms of magnesium and carbon are dependent on the abundance of hydrogen in the Sun’s photosphere. 
• Any variation in the helium content directly affects the abundance of hydrogen.
• If the helium abundance increases, the relative abundance of hydrogen decreases.
  • This reduction in hydrogen availability impacts the formation of molecules like MgH and CH, and also lowers the opacity of the Sun’s photosphere.

Source: PIB