ISRO Missions and Discoveries

Detection of Fluorine in hot Extreme Helium (EHe) Stars


From UPSC perspective, the following things are important :

Prelims level: Extreme Helium (EHe) Stars

Mains level: NA

A study by the Indian Institute of Astrophysics (IIA) has detected the presence of singly ionized fluorine for the first time in the atmospheres of hot Extreme Helium Stars.

UPSC may ask a simple statement-based question considering the following points:

If there is the presence of hydrogen, their abundance in universe and how it is different from neutron stars etc.

What are EHe stars?

  • An extreme helium star or EHe is a low-mass supergiant that is almost devoid of hydrogen, the most common chemical element of the universe.
  • There are 21 of them detected so far in our galaxy.
  • The origin and evolution of these Hydrogen deficient objects have been shrouded in mystery.
  • Their severe chemical peculiarities challenge the theory of well-accepted stellar evolution as the observed chemical composition of these stars do not match with that predicted for low mass evolved stars.

Why is the study significant?

  • Clues to the evolution of extreme helium stars require accurate determinations of their chemical composition, and the peculiarities, if any, become very important.
  • Fluorine plays a very crucial role in this regard to determine the actual evolutionary sequence of these hydrogen deficient objects.
  • The scientists explored the relationship of hot EHes with the cooler EHes, based on their fluorine abundance and spotted it in the former, thus establishing an evolutionary connection across a wide range of effective temperature.
  • This makes a strong case that the main form of these objects involves a merger of a carbon-oxygen (CO) and a Helium (He) white dwarf.
  • The detection of enhanced fluorine abundances in the atmospheres of hot EHes solves a decade-old mystery about their formation.

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