Why in News:

• Indian Institute of Astrophysics, Bengaluru, researchers have found support for one way to understand the aberrant behaviour of Blue Straggler stars.
• For this, the researchers also made use of the observations by the UVIT instrument (UltraViolet Imaging Telescope) of ASTROSAT, India’s first science observatory in space.

To read about ASTROSAT: https://officerspulse.com/astrosat/

What are they?

• Blue stragglers are a particular type of star seen in clusters and also, sometimes, alone.
• These classes of stars are  observed in old, dense stellar systems such as globular clusters. They stand out because old stellar populations are expected to be devoid of blue (high-mass) stars which possess very short lifespans.
• The blue stragglers in an old stellar population must therefore have formed long after the system as a whole.
• But, Blue stragglers, a class of stars on open or globular clusters, stand out as they are bigger and bluer than the rest of the stars.· 
• These are a few stars that, just at the stage of their lives, when they are expected to start expanding in size and cooling down, do just the opposite. They grow brighter and hotter as indicated by their blue colour, thus standing out from the cooler red stars in their vicinity in the colour-magnitude diagram.
• Since they lag behind their peers in evolution, they are called stragglers, more specifically, blue stragglers, because of their hot, blue colour.
• Omega Centauri is the most luminous and massive globular star cluster in the Milky Way. 

Related Information

Comparison to sun

• Sun, for example, is what is called a main sequence star, and, given its mass and age, it is expected that once it has converted all its hydrogen into helium, its core will get denser, while outer layers expand.
• So, it will bloat into a red giant. 
• After this phase, its fuel spent, it will shrink, becoming a smaller, cooling star called a white dwarf star at the end of its life. 
  • The Sun would need to be about 20 times more massive to end its life as a black hole. In some 6 billion years it will end up as a white dwarf — a small, dense remnant of a star that glows from leftover heat. The process will start about 5 billion years from now when the Sun begins to run out of fuel.
  • The Sun will start to run out of hydrogen in its core to fuse, and it will begin to collapse. This will let the Sun start to fuse heavier elements in the core, along with fusing hydrogen in a shell wrapped around the core. When this happens, the Sun’s temperature will increase, and the outer layers of the Sun’s atmosphere will expand so far out into space that they’ll engulf Earth.
  • Subrahmanyan Chandrasekhar, an eminent Indian scientist  proved that there was an upper limit to the mass of a white dwarf. This limit, known as the Chandra limit, showed that stars more massive than the Sun would explode or form black holes as they died.
  • In 1983, Subrahmanyan Chandrasekhar was awarded the Nobel Prize in Physics for his work on the physical processes involved in the structure and evolution of stars.

References:

1. https://dst.gov.in/blue-straggler-bigger-and-bluer-star-formed-when-one-star-eats-another
2. https://astronomy.swin.edu.au/cosmos/b/blue+stragglers
3. https://www.thehindu.com/sci-tech/science/what-makes-blue-straggler-stars-tick/article65344766.ece