It's interesting how heavy stars turn into supernovae, black holes, and neutron stars, whereas average stars like the sun end life as a white dwarf surrounded by a disappearing planetary nebula.
Stars undergo a natural cycle of transformation, much like any living being. This cycle begins with birth, expands through a lifespan characterized by growth and change, ultimately leading to its death. Every star, however, follows roughly the same basic seven-stage life cycle, starting as a gas cloud and ending as a star remnant. Let us discuss the life cycle of stars and their different stages.
A Giant Gas Cloud
A star begins life as a large cloud of gas. The temperature inside the cloud is low enough for the synthesis of molecules. Some of the molecules, like hydrogen, light up and allow astronomers to see them in space. The Orion Cloud Complex in the Orion system serves as a nearby example of a star in this stage of life.
Protostar
When the gas particles in the molecular cloud run into each other, heat energy is produced. This results in the formation of a warm clump of molecules called the Protostar. The creation of Protostars can be seen through infrared vision as the Protostars are warmer than other materials in the molecular cloud.
T-Tauri Phase
In the T-Tauri stage, a young star begins to produce strong winds, which pushes away the surrounding molecules and gas. This enables the forming star to become visible for the first time. Scientists can spot a star in the T-Tauri stage without the help of infrared or radio waves.
Main Sequence
The main sequence phase is the stage in development where the core temperature reaches the point for the fusion to commence. In this process, the protons of hydrogen are converted into atoms of helium. This exothermic reaction gives off more heat than it requires and so the core of a main-sequence star releases a tremendous amount of energy.
Red Giant
A star converts hydrogen atoms into helium over its course of life. Eventually, the hydrogen fuel runs out, and the internal reaction stops. Without the reactions occurring at the core, a star contracts inward through gravity causing it to expand. As it expands, the star first becomes a subgiant star and then a red giant with cooler surfaces than the main-sequence star, and owing to this, they appear red and not yellow.
Fusion of Heavier Elements
Helium molecules fuse at the core, as the star expands. The energy of this reaction prevents the core from collapsing. The core shrinks and begins fusing carbon, once the helium fusion ends. This process repeats until iron appears at the core and it absorbs energy, which causes the core to collapse. This implosion transforms massive stars into a supernova while smaller stars like the sun contract into white dwarfs.
Supernovae and Planetary Nebulae
Most of the star material is blasted away into space, but the core implodes into a neutron star or a singularity known as the black hole. Less massive stars don’t explode, their cores contract instead into a tiny, hot star known as the white dwarf while the outer material drifts away. Stars tinier than the sun, don’t have enough mass to burn with anything but a red glow during their main sequence.
Whether small or big, old or young, stars are one of the most beautiful and lyrical objects in all of creation.
