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SPIRAL GALAXY BARS MAY PREVENT NEW STARS

Focus: GS-III Science and Technology

Introduction

  • Stars are fundamental building blocks of galaxies and the seeds of these stars are clouds of cosmic dust and gas.
  • Stars are scattered all around the galaxies, and the galaxies themselves are of different types: star-forming spiral galaxies and non-star-forming lenticular and elliptical galaxies.
  • In some spiral galaxies, the stars move in elongated orbits near the centre so that, from far, this portion appears like an illuminated bar.
  • Nearly two-thirds of the disc galaxies in the local universe are found to have this bar structure.

Role of bars

  • The Milky Way is a barred spiral galaxy. Since not all spiral galaxies have bars, the role of bars – why they exist, what triggers their formation and whether they foster star formation are interesting questions.
  • Some barred galaxies have shown a higher concentration of newly formed stars, suggesting that the bar nurtures star formation.
  • The present work studies four such barred galaxies out of which three, in fact, appear to prevent stars from forming at their central region covered by the length of the bar.
  • Using data from multiple telescopes, including the Very Large Array, New Mexico, in the US, the IRAM 30 metre telescope, Sierra Nevada, Spain, Sloan Digital Sky Survey etc, the authors study the gas content and star formation along the bar region of four barred spiral galaxies.
  • In three of the four observed galaxies, they find that the region covered by the length of the bar does not have enough gas (Hydrogen in the atomic form and molecular hydrogen, which is believed to condense and form stars).
  • The researchers do not see the same depletion of gas and stars in the fourth galaxy. The reason, they believe is that this galaxy does not have an old enough bar.

-Source: The Hindu

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December 2022
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