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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