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HE-ENHANCED COOL BRIGHT STARS DISCOVERED

Focus: GS-III Science and Technology

Why in news?

A team of scientists from the Indian Institute of Astrophysics (IIA) studied numerous stars of this cluster and discovered He-enhanced cool bright stars among the metal-rich sample of Omega Centauri.

Details and Significance

  • Though there are estimations of He-enhancement in the H-core burning main-sequence stars (like Sun) of Omega Cen, this is the first-ever spectroscopic determination of He-abundance in Omega Centauri.
  • The study provides a very important clue for the origin of the He-enhanced population establishing that these are the second generation of stars formed from the metal-rich and He-enhanced material from the first generation of stars.

Background

  • Globular clusters are the stellar systems with millions of stars formed from the same gaseous cloud.
  • Hence, usually, the stars formed will be homogeneous in their chemical composition of elemental abundances.
  • But there are clusters which deviate from this norm. One is being Omega Centauri, the brightest and the largest globular cluster in our Galaxy, the Milky Way.
  • The different stars of Omega Centauri do not show the same metal content, a parameter that indicates its age, but a large range in it.
  • Due to the anomalous elemental abundances, the formation scenario may be different from normal.
  • Normally, the abundances are derived using the assumption that He is one-tenth of the H-abundance.
  • While in most stars, H is the most abundant element, if the abundance of H is reduced, correspondingly He abundance increases because the sum of H and He is a constant, and the other heavier elements are in traces.
  • However, they found that the H-atomic spectral lines are very strong in the spectra of stars, and the reliable measurement of abundance was not possible from such lines.
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September 2022
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