Stars: Birth to Death

It does not take an expert eye to discover the magnificence of the night sky. It has so much to offer, in the form of its pitch black darkness adorned by equally bright dazzling dots what we more commonly know as stars. Stars are probably the most amazing celestial creations. They embellish the vast emptiness of the sky with their charming hues and brightness so efficiently that they still remain the centers of attraction to astrologers, scientists and philosophers.

Early philosophers believed that stars are gods, who constantly show up in the night skies to impose their presence by brilliance and to inspire people do good deeds for the next day. This is of course not a valid proposition anymore on scientific grounds. So what actually a star is?

Stars Dominate the Night Sky

Astrophysicists use observations to suggest theories of how stars come into being. Interstellar space is not a perfect vacuum as you might expect. Rather it is a low density mixture of atoms, molecules and microscopic specks of dust. In places these form greater concentrations, which appear as large gas clouds.

Interstellar Gas Clouds

A close look at the night sky with a telescope reveals the existence of the gas clouds along with stars and planets. The most available element in these clouds is hydrogen. The most plausible theory is that stars begin as clouds of hydrogen.

Despite the extreme tenuousness of these clouds, gravitational force is predominant force that acts on the particles of the cloud. This pulls the particles together and they accelerate inwards. They collide increasingly frequently sharing their energy. The temperature of the gas thus rises. Therefore gravitational energy is converted to thermal energy. When the gas cloud collapses sufficiently it becomes hot enough to emit infrared radiation. This causes electrons to be stripped off the hydrogen atoms and the atoms eventually become hydrogen nuclei (i.e. protons). This causes the whole mass of the cloud to be converted into a mixture of positive ions and negative electrons called Plasma. At this stage the gas cloud can be called: a Protostar.

Collisions between particles become increasingly energetic as the gravitational contraction continues. If the mass of the cloud is high enough, eventually an ignition temperature of about 10 million Kelvin is reached, which gives the hydrogen nuclei sufficient energy to overcome electrostatic repulsion and join together to start the process of nuclear fusion. This process releases a large amount of energy owing to decrease in potential energy due to strong nuclear force. This maintains or increases the core temperature of the gas clouds so that fusion reactions continue. At the ignition temperature, the hydrogen nuclei fuse to form stable helium. The overall reaction involves four hydrogen nuclei fusing together to form a single helium.
As soon as the nuclear fusion process initiates, the gas cloud can be termed as a star. The core of a star is a fusion reactor. Iron is the largest nucleus that can release energy on formation in this way. When the helium in the core of the stars is used up to form heavier elements, the star collapses on itself to become a white dwarf star. This can be marked as the death of the star.

A White Dwarf (Left)

Stars continue shocking us as we explore and understand more plausible theories that unveil secrets of their origin, evolution and death. Our knowledge of celestial objects is still at its infancy. Until we get the exact and most accurate information that define the existence of all celestial bodies from black holes, planets to stars correctly, I suppose it is safe to sing-

      “Twinkle twinkle little star;
How I wonder what you are?”

----
By Mahmud Hasan
Aftermath Publications
----
The Aftermath Publications, Issue 2
----