In a progressive breakthrough for global astrophysics, scientists at the Indian Institute of Astrophysics, Bengaluru, have discovered surprising information about the evolution of the Blue Straggler Star. This discovery was made possible through the observations conducted by the Ultraviolet Imaging Telescope (UVIT) of Astrosat, the first-ever space science observatory launched by India.
Back in September 2021, these Indian researchers proposed a hypothesis for the evolution of blue straggler stars, marking the commencement of the first comprehensive analysis of these celestial entities.
The Unconventional Evolution of Blue Stragglers
Blue Straggler Stars are unique celestial bodies characterized by their hot, blue color and massive size. Notably, unlike other stars, Blue Stragglers seem to defy the traditional trajectory of evolution. Contrary to the expectation that stars expand in size and cool down over time, Blue Stragglers grow brighter and hotter, thereby standing out from the cooler red stars in their surroundings. Because they appear to “lag” behind in their evolutionary journey compared to other stars, these entities have been denoted as stragglers.
The discovery of Blue Stragglers can be traced back to the early 1950s, with astronomer Allan Sandage stumbling upon them in the globular cluster M3. These stars are estimated to be at least 12 billion years old and are situated several thousand light-years away from the sun.
Exploring the Peculiarities of Blue Stragglers
Several hypotheses have been proposed to explain the unusual behaviour of Blue Stragglers. One theory suggests that these stars might not belong to the original star family in the cluster, thereby explaining their different properties. Another hypothesis posits that if Blue Stragglers are indeed part of the group, their peculiarities could be attributed to these stars gaining mass from a binary companion. Here, the straggler draws matter from the companion star, leading to an increase in mass and a shift towards hotter and bluer hues. Concurrently, the red giant evolves into a regular or smaller white dwarf. Recent research has confirmed the presence of white dwarf companions to blue stragglers. Another theory proposes the existence of a third star assisting in the transfer of matter between the straggler and its companion.
Studying Star Age and Evolution
To investigate the behavior and evolutionary journey of a star, scientists often resort to plotting a graph known as the Hertzsprung-Russell diagram. This graph, which charts the star’s color against its magnitude, provides insights into the star’s surface temperature and the total energy it emits. As an example, our Sun—a main sequence star—will, after converting all hydrogen into helium, eventually expand into a red giant before shrinking into a white dwarf at the end of its life.
About Indian Institute of Astrophysics
The Indian Institute of Astrophysics (IIA) is a self-governing research institute situated in Bengaluru and funded entirely by the Department of Science and Technology, Government of India. Established in 1971, the IIA primarily concentrates on research in astronomy, astrophysics, and related fields.