Blue Straggler Stars

In News

• Recently, Scientists at Indian Institute of Astrophysics, Bengaluru, have found support for one way to understand peculiarity about Blue Straggler Star.
  • The researchers also made use of the observations by the UVIT instrument (UltraViolet Imaging Telescope) of ASTROSAT(India’s first science observatory in space).

About Blue Straggler Stars

• They are a class of stars on open or globular clusters that stand out as they are bigger and bluer than the rest of the stars.
  • They have intrigued scientists who have for long probed their origin.
• It is found in old star clusters and appears to be lagging behind most of the other stars in the cluster in its evolution toward a cooler, reddish state. 
  • Blue stragglers tend to be strongly concentrated toward the centre of the cluster. 
• Formation:
  • A bunch of stars born at the same time from the same cloud form a star cluster.
  • As time passes, each star evolves differently depending on its mass. 
  • The most massive and bright stars evolve and move off the main sequence creating a bend in their track, known as the turnoff. 
  • Stars above this bend or brighter and hotter stars are not expected in a cluster, as they leave the main sequence to become red giants. 
  • But in 1953, Allan Sandage found that some stars seem to be hotter than the turnoff of the parent cluster. 
  • Initially, these blue stars still straggling above the turnoff were not part of these clusters. 
  • However, later studies confirmed that these stars are indeed cluster members, and they were termed “Blue Stragglers”. 

About the Study

• They do not belong to the family of stars in the cluster, and hence are not expected to have the group properties.
  • But if they actually belong to the group, the evasive behaviour is due to these stars gaining mass from a binary companion.
• The straggler draws matter from the giant companion star and grows more massive, hot and blue, and the red giant to end up as a normal or smaller white dwarf. 
• The straggler draws matter from a companion star, but there is a third star that facilitates this process.
• The IIAP researchers have shown evidence that supports the second of the hypotheses listed above.

Relevance of the study 

• The study will help improve understanding of these stellar systems to uncover exciting results in studies of large stellar populations, including galaxies.

Source:TH