The Stars
The Composition of Stars:
Astronomers have determined, with the use of special instruments, such as the
spectroscope, that all stars have the same basic chemical make up.
The most common and abundant element is hydrogen. It makes up from 60-80% of
the total mass of a star. Helium is the second most abundant element. The
combination of helium and hydrogen accounts for 96-99% of the star's total mass.
The rest of the star's mass is made up of other elements such as oxygen, neon,
carbon, and nitrogen.
How and Why Stars Shine:
Within the core of a star, gravity works in pulling together the atoms of
hydrogen gas so tightly that they become fused together. This process is known
as Nuclear Fusion. During nuclear fusion, hydrogen atoms are fused
together to form helium atoms. Our Sun changes about 600 billion kg of helium
into 595.8 billion kg of helium, every second. It seems that 4.2 billion kg of
matter is lost every second. What is actually happening is that this missing
matter is being changed into energy in the form of heat and light. It is this
light that also gives off infrared rays, ultraviolet rays, radio waves, as well
as radio waves.
The
Life and Death of Stars: (an E.T. true story)
Stars
change over time. These changes however may take anywhere from a few million
years to a few billion years. Based on astronomical evidence coupled with
various theories, scientists believe that stars are born out of gases from a
nebula. Over time, the hydrogen gas becomes clumped together by the forces of
gravity. Over millions of years or more, more and more hydrogen gas is pulled
together to form a spinning cloud of gas. Collisions between the hydrogen atoms
become more frequent, causing the cloud to heat up. When the temperature within
this cloud reaches about 15 000 000 C, nuclear fusion begins. The heat given off by this process results in a
new star being formed. The star is now known as a Protostar.
The
main factor that determines the life, death, and eventual size of a star is the
amount of matter that it started off with.
