New Delhi: A team of scientists from the Indian Institute of Astrophysics (IIA), an autonomous institute under the Department of Science & Technology (DST), Government of India studied numerous stars of this cluster and discovered He-enhanced cool bright stars among the metal-rich sample of Omega Centauri. This work, a result of the spectroscopic survey conducted of this cluster, determines the He-abundance of these stars for the first time and has been published in ‘The Astrophysical Journal’.
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.
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. And, also that the He-enhanced main-sequence stars evolve to the metal-rich He-enhanced cool bright stars as our program starts.
