With reference to Blue Straggler Stars, consider the following statements -
- They are typically found in young, sparse stellar systems such as open clusters.
- They appear bluer, hotter, and brighter than the main-sequence turn-off stars in their cluster.
- One proposed mechanism for their unusual behaviour is mass transfer from a giant companion star.
Which of the statements given above is/are correct?
Explanation - Blue Straggler Stars are hot, blue, massive stars seem to have a different trajectory of evolution from the norm. These are a class of star observed in old, dense stellar systems such as globular clusters. They lie on an extension of the main sequence star and are bluer and brighter than the main-sequence turn-off stars. These objects are found in star clusters, dwarf galaxies, and in the field. How are they Different? There are a few stars, 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 the evolution, they are called stragglers, more specifically, blue stragglers, because of their hot, blue colour. Why they Behave Differently? Possibility 1: They do not belong to the family of stars in the cluster, and hence not expected to have the group properties. Possibility 2: 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. Possibility 3: The straggler draws matter from a companion star, but that there is a third star that facilitates this process.
Explanation - Blue Straggler Stars are hot, blue, massive stars seem to have a different trajectory of evolution from the norm. These are a class of star observed in old, dense stellar systems such as globular clusters. They lie on an extension of the main sequence star and are bluer and brighter than the main-sequence turn-off stars. These objects are found in star clusters, dwarf galaxies, and in the field. How are they Different? There are a few stars, 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 the evolution, they are called stragglers, more specifically, blue stragglers, because of their hot, blue colour. Why they Behave Differently? Possibility 1: They do not belong to the family of stars in the cluster, and hence not expected to have the group properties. Possibility 2: 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. Possibility 3: The straggler draws matter from a companion star, but that there is a third star that facilitates this process.
