Stars


Comparison of various celestial bodies. VY Canis Majoris is the largest star in the universe.

1. Mercury < Mars < Venus < Earth

2. Earth < Neptune < Uranus < Saturn < Jupiter

3. Jupiter < Wolf 359 < Sun < Sirius

4. Sirius < Pollux < Arcturus < Aldebaren

5. Aldebaren < Rigel < Antares < Betelgeuse

6. Betelgeuse < Mu Cephei < VV Cephe < VY Canis Majoris

A star is a huge, massive ball of fire lit up due to “fuels” like hydrogen, helium or any other element held together by gravity. Due to the “holding together by gravity”, stars have a massive gravitation pull, like how the Sun holds Earth and the other planets, preventing them from floating away.

A star is formed through a nebula, a “cloud” found in galaxies. Whenever we see a nebula, we know that a star is about to be formed. A star is very hot at its young age, but gradually over time, it begins cooling down. An example of a nebula is the Orion nebula.

 

The Orion Nebula

However, in main sequence stars (i.e stars that have a medium size like the sun), it is found that the heat and the luminosity is increasing ,but at a slow pace. Also in the future, if this continues, then a star will grow into a red giant, which is 1000 times its original size, which forms into a planetary nebula over time, and then turns into a white dwarf. It then cools down to form a black dwarf.

In massive stars, they go out with a big bang known as the Supernova. Massive stars have a smaller life compared to main sequence stars, due to the huge amount of fuel needed to charge up the core of the star. They too form red giants in the course of time but explodes into a supernova, as said. Even after the explosion, the core of the star remains, thereby deciding the fate of the core of the star, changing either into a neutron star or a black hole.

Life cycle of a star

Characteristics

1. Age :- Most stars have an age between 1 billion and 10 billion years old. Some stars have even reached an age of 13 billion years old, which is the age of the universe! The oldest star discovered is HE 1523-0901, which is estimated to be 13.2 billion years old. As said, the more massive the star, the shorter it’s lifespan due to the pressure exerted in the core.

2. Chemical composition:- Mostly, stars in the universe is said to have two elements, hydrogen and helium. However, in some stars they are said to also have presence of iron, chromium and rare earth elements.

3. Size :- Although most of the stars are much bigger than the Sun they appear to be shiny dots in the sky due to the distance between Earth and the star. Since the sun is much closer to Earth, the Sun appears to bigger than other stars. In reality, Betelgeuse is 650 times larger than the Sun.

4. Temperature :- Main sequence stars generally have a lower temperature compared to massive stars. Massive stars have an average temperature of 50,000 K while main sequence stars have an average temperature of a few thousand K.

HE 1523-0901( The oldest star)

Sirius A and B

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By melvina06

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