Red Giant Star Betelgeuse UPSC NOTE

 Red giant star Betelgeuse

  • Betelgeuse is a red supergiant star of spectral type M1-2 and one of the largest visible to the naked eye.

  • It is usually the tenth-brightest star in the night sky.

  • After Rigel, the second-brightest in the constellation of Orion.

  • It is a distinctly reddish, semiregular variable star.

  • Its apparent magnitude, varying between +0.0 and +1.6, has the widest range displayed by any first-magnitude star.

  • It is also called ‘Thiruvathirai’ or ‘Ardra’ in Indian astronomy.

  • In 1920, Betelgeuse became the first extrasolar star whose photosphere's angular size was measured.

How star ‘dies’ and collapses into a supernova?

  • A star is born from a dense cloud of gas and dust called a nebula.

  • Most stars, including the Sun, through nuclear fusion, fuse the simplest element in the universe, hydrogen — to produce helium and some energy as a byproduct. 

  • This energy’s outward push balances gravity’s inward pull, and keeps the star from collapsing.

  • As the star exhausts its hydrogen fuel, it expands and becomes a red giant.

  • In this phase, it fuses helium into heavier elements like carbon and oxygen.

  • While smaller stars, like Sun, eventually shed their outer layers and form a white dwarf.

  • Larger stars undergo a supernova explosion.

  • In supernova explosion their cores collapse and release an immense amount of energy. 

  • This explosion disperses heavy elements into space and may result in the formation of a neutron star or a black hole.

Stage of Betelgeuse

  • Massive stars like Betelgeuse run out of hydrogen fuel in only a few crore years, after which they switch to using helium to make carbon. 

  • The energy released in the fusion of helium is less than that of hydrogen, so the star burns more helium to stay stable and not collapse. 

  • The helium runs out in about ten lakh years. 

  • At this time, red giants like Betelgeuse burn carbon, then silicon, and briskly consume one by one the elements of the periodic table, until finally their core brims with iron — whose fusion requires more energy than it releases — and some cobalt and nickel.

  • Each of these stages is shorter than the predecessor. 

    • In a star like Betelgeuse, carbon burns in a few hundred years.

    • Silicon lasts about a day. 

  • Therefore, the late-carbon stage is the terminal phase of Betelgeuse.

  • Once the core is rich in iron, the temperature and pressure within the star drops. 

  • With nothing to stop it, gravity compresses the core and turns it into a neutron star or a black hole. 

  • The shock wave resulting from the collapse blasts the surrounding layers into interstellar space and the star explodes in a celestial firework display.



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Learnerz IAS | Concept oriented UPSC Classes in Malayalam: Red Giant Star Betelgeuse UPSC NOTE
Red Giant Star Betelgeuse UPSC NOTE
Learnerz IAS | Concept oriented UPSC Classes in Malayalam
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