MSV-2035 Astronomy Document - Inside Design - FINAL - FINAL

Astronomy & Astrophysics 44 4.1.5 StellarClusters Globular clusters (GCs) are densely packed collections of ancient stars. Roughly spherical in shape, these contain hundreds of thousands, and sometimes millions, of stars. Studying them helps astronomers estimate the age of the Universe or figure out where the center of a galaxy lies. RR Lyrae stars are low-mass, typically metal poor, Population II stars that are located within the so-called classical instability strip. Their apparent large-amplitude brightness changes are due to oscillation in the radial modes: radial fundamental mode (RRab stars) or radial first overtone mode (RRc stars) or simultaneous pulsation in these two radial modes (RRd stars) makes them as excellent distance indicators. Identification of new RR Lyrae stars belonging to GCs, study of the nature of oscillations and determination of physical parameters have been some of the key topics of research in the study of GCs. Another class of intriguing stars are the blue straggler stars (BSS). These are stars that are more luminous and hotter (bluer) than the stars at the main sequence turnoff in clusters, i.e. they appear to be younger than the other stars in the cluster. One explanation is that these are stars that have been formed through merger of stars within the cluster. However, in the case of less dense star clusters and in outer regions of the clusters, there still could be some BSSs formed via mass transfer. Using the far-UV capabilities of the AstroSat, Indian astronomers detected far UV bright BSSs in star clusters, measured their basic parameters and showed some of them to bemass transfer systems. Open clusters (OCs) are collections of stars that share similar ages, chemical compositions, and are at similar distances from us. These qualities make open clusters important cosmic laboratories for studies of fundamental astrophysics such as: the formation of stars, stellar evolution, dynamical interactions between stars, and the chemical and dynamical evolution and structure of the disc of the Milky Way. The study of open clusters of the stars is a traditional field with astronomers in the country. The findings of their studies include determining the cluster membership, stellar population and age of the cluster, study of variable stars in the cluster, and the structure of the Galactic disc. 4.1.6 StellarAbundances andChemodynamics of theGalaxy The study of stellar abundances and Galactic kinematic and chemical evolution have been the main forte research of several astronomers in the country. Detailed abundance analysis of metal-poor stars through targeted surveys have led to new understanding of these objects. For instance, the observed abundance patterns of some of the carbon enhanced metal poor (CEMP) stars showed that abundance pattern in these objects are well reproduced with the i-process model predictions.Analysis based on different elemental abundance ratios confirmed low-mass formerAGB companions for these objects. A detailed study of abundances in the globular cluster Omega Centauri led to the discovery of helium rich stars in the cluster. This discovery is of importance as it indicates multiple populations in the globular cluster contrary to the general belief of these objects having a single population. Indian astronomers have also made important contributions to measuring the abundance pattern in metal poor gas in the early Universe that are compared withGalacticmetal poor stars to understand the early chemical history. In a recent study led by Indian astronomers, robust observational evidence was provided which indicated that Li MEGA SCIENCE VISION-2035 asteroids that seem to be like rubble piles. Simulation based work on instabilities in the ISM that eventually lead to formation of stars has been done by several groups. These detailed calculations useMHD simulations in a multi-phase ISM.