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.

What is the Constellation Orion?

• Constellation:
  • A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.
    • They are useful in assisting astronomers and navigators to locate certain stars
  • Officially, there are 88 recognized constellations in the night sky. These constellations were defined and established by the International Astronomical Union (IAU).
    • IAU was founded in 1919, headquartered in Paris, France.
• Constellation Orion:
  • It is a prominent constellation that can be seen throughout the world.
    • It is located on the celestial equator and is best visible in the evening sky from January to April in the Northern Hemisphere, and from November to February in the Southern Hemisphere.

Source: TH