Red Supergiant Star Betelgeuse | 21 Jun 2023

Why in News?

The bright red star Betelgeuse, known as 'Thiruvathirai' or 'Ardra' in Indian astronomy, captivates observers with its prominent position in the constellation Orion.

• Recent research conducted by Japanese and Swiss researchers has shed light on the star's pulsation patterns.

What is Betelgeuse's Pulsation?

• About Betelguese:
  • Betelgeuse is a red supergiant star that is nearing the end of its life. It is the second-brightest star in the constellation of Orion, after Rigel.
    • Scientists noticed that Betelgeuse was mysteriously dimming in late 2019 following a traumatic outburst caused by the star blowing off a large portion of its visible surface.
  • Betelgeuse varies in brightness because of two main factors: changes in its surface temperature and changes in its size.
    • As a red supergiant, Betelgeuse has a very unstable outer layer that is prone to convection and pulsation.
• The Pulsating Mechanism:
  • The pulsation of Betelgeuse refers to the periodic contraction and expansion of the star.
    • Researchers have compared the observed pulsation of Betelgeuse to theoretical estimates, indicating that the star is in its late carbon-burning stage.
    • Pulsation periods provide valuable insights into the star's radius, luminosity, and mass, affirming its current phase of core carbon-burning.
  • Similar to a pot's lid lifting to release steam, red giant stars expand and contract due to heating and cooling of hydrogen in their outermost layers.
    • The star's outermost envelope contains cooler neutral hydrogen, which absorbs heat from the interior, causing the star to expand.
  • As the temperature rises, hydrogen becomes ionised and can absorb more heat, leading to a forceful expansion and ejection of the outermost shell.
  • The cyclic nature of this process results in periodic dimming and brightening of the star, observable from a distance.
• Stages of Evolution:
  • Stars like Betelgeuse fuse hydrogen into helium during their initial stages, which helps maintain a balance between gravity and energy release.
  • Massive stars like Betelgeuse run out of hydrogen fuel in a few crore years, when they switch to using helium to make carbon. Helium runs out in about 10 lakh years.
    • As each stage progresses, the burning of elements becomes faster, with carbon burning in a few hundred years and silicon burning in about a day.
      • Afterwards red giants briskly consume one by one the elements of the periodic table, until finally their core brims with iron.
    • Once the core is rich in iron, the temperature and pressure within the star drop. With nothing to stop it, gravity compresses the core and turns it into a neutron star or a black hole.
  • Betelgeuse's late-carbon stage signifies the terminal phase before the star's imminent collapse.

Source: TH