The Entire Life Cycle Of A Star From Birth, Transformations, to Death: A Complete Walk Through

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Stage 1 - Huge gas cloud or Nebula Cloud

All stars, including our Sun, were first just a huge gas cloud in the vastness of space. These gas clouds are called “Nebula Cloud,” they mainly consist of hydrogen and helium. Nebula is either formed from clouds of cold and interstellar dusts and gases or formed after an explosion of another star, a supernova. Just like normal clouds here on earth, Nebulas are always on the move, so they are always churning and revolving around each other. Nebulas can also be extremely hot; a well-known Nebula called the “Orion Nebula” is around 9726’C which is nearly twice as hot as the temperature on the surface on our sun. The lifespan of a Nebula is around 20,000 years to an astonishing 80,000 years. It is believed that there are around 20,000 nebulas in the Milky-Way, our galaxy, alone.

Stage 2, Protostar

After thousands of years of churning the mixing the Nebula creates a magnetic field and a strong gravitational pull, Since the gravitational pull is so immense it collapses in into itself. This is called Accretion. At the centre of the collapsing nebula cloud is a protostar. A protostar is a very young star which is still gathering mass and gas from its Nebula cloud. The protostar still hasn’t got enough energy to star Nuclear Fusion, but it gives our heat and light by gravitational potential energy, which is then converted to heat, and this is what the protostar radiates. This is process can take between 100,000 years or up to 10 million years depending on the mass of the protostar.

Stage 3, T-Tauri

This is the third stage of a star, The T-Tauri stage is when the young star is in between a protostar and becoming into a Main Sequence star. The star is still incredibly young, only being less than 10 million years old. It is still gaining its gaining mass from its Nebula cloud but not as much as it did before. At this stage, the young star will finish or still be creating its proto planetary disc where future planets will form and orbit the sun. this rings on the proto planetary disc are created by very young planets where it is carving out and taking in mass from the disc. With strong Steller winds and radiation most of the Nebular cloud blown away only leaving some behind for the young star.

Stage 4, Main sequence star

A Main Sequence Star is a fully matured and developed star. This stage is when the star has is currently undergoing nuclear fusion. Nuclear Fusion in a Star is when a hydrogen nuclei and other nuclei fuse due to immense pressure and heat creating helium atoms which radiates energy giving of heat and light in the process. This is the Star’s longest stage lasting between anywhere from 10 billion years all the way to 100 billion years depending on the mass of a star. A red dwarf main sequence star with only half the mass or less of our sun can last for 100 billion years in this stage. A grade G star, including our sun, which is a yellow star can last 20 billion years in this stage. A Blue or Red supergiant star can last for only 10 billion years as they are not very energy efficient. A red star is the coldest star and a Blue star the hottest star.

Stage 5, Red/Blue Giant

At this stage the star has no longer have enough hydrogen gas to undergo nuclaer fusion. The out layers of a star will swell and the sun physically gets larger, it can get 100s or 1000s of times larger. Our Sun in 5 billion years will also become a Red giant too, consuming mercury, venus and potentially Earth too meaning only leaving Mars and the other planets left in the solar system. A star will only be a Red or Blue Supergiant for a billion years or less since it is burning its last reserves. This is one of the shortest stages during a Star’s stellar evolution. As the Star becomes a super giant it will loss its mass and its gravitational pull on its planets meaning its gravity gets weaker as it expands.

Stage 6, Supernova

At this stage, the star starts to burn heavier elements such as iron. Reaction with iron in the core requires energy, an endothermic reaction, which causes the Star’s core to collapse. When the core collapse Massive stars like a blue giant will implode under its own gravitational pull and smaller stars like our Sun will contract leaving behind a white dwarf. The explosion is so hot it can reach up to 1 billion degrees, vaporising anything in its path including planets. A Supernovae can forge new heavier elements such as iron, gold, platinum and more. If a star near us, not the sun, turns into a supernova it can light the Earth’s sky for over a week.

Stage 7 (part 1), Black hole

Black holes are a remnant from a supernova. There are two types of black holes, one is Stellar Black holes and the other is Super Massive Blackholes. Stellar black holes are normally 3 or 12 times the mass of our sun and they are scattered all over the Milky Way and other galaxies. Super Massive Blackholes are around 100,000 to a billion masses of our Sun commonly found at the centre of a galaxy like the Milky Way. Black holes are still being studied by many Scientists but still mostly remain as a mystery. The gravitational pull on a black hole is so immense that even light cannot escape it. The disk around the Blackhole is called the horizon. The horizon emits and glows as the objects are orbiting the blackhole gets extremely hot. At the centre of a Blackhole is the singularity where all the matter ends up it. The singularity is very small but has infinite space. The laws of physics as we know cease to function in the singularity of a Blackhole as space and time bends and twists.

Stage 7 (part 2), Neutron Star

Neutron Star is also a remnant of a s supernova explosion but instead of a blackhole, the star’s core survives. The core gets so dense it crushes the electron and protons of every atom into a neutron. Neutron star is one of the densest objects found in the universe. It is so dense that one teaspoon of a Neutron Star can weigh about 10 million tons. Neutron Star does not produce heat, but it cools down very slowly. They are normally around 50,000’C or plus. The atmosphere emits light because the atmosphere is in a state called plasma, but the surface is not plasma so cannot produce heat. At the poles of the star the Neutron star emits ionising electromagnetic waves.

Stage 8, The cycle repeats

Once a Supernova explodes I can sometimes, very rare, leaving a Diffuse Nebula. A Diffuse Nebular contain mostly of heavier elements but some gases such as helium and hydrogen which is enough to make a very small star like a Red dwarf. It is thought that our Star, the Sun, is a 3rd generation star meaning that there was 3 stars in our Sun’s place before it exploded and, in the process, creating our star. Once a supernova explosion has happened it sends out shock waves which can trigger other Nebula Clouds across the galaxy to form new stars.

The end, now you know the full life cycle of a Star. Next time when you think about the Sun just imagine how complex and beautiful our Star really is. Thank you.

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