Page 45 - Reading Success B6

The Sun is at the center of the Solar System. The planets and other heavenly
objects in the Solar System are bound to it by gravity. These objects, including the
Earth, orbit the Sun. The Sun is a medium-sized star. It burns very brightly, and its

energy is responsible for all life on Earth.The Sun’s surface has a temperature of
around 5,800 Kelvin, or around 5,500 degrees Centigrade. Because of its very
high temperature, the Sun appears to be white in color. The Sun’s surface is
mostly made up of hydrogen and helium. Hydrogen makes up around 74 percent
of its mass. Helium is responsible for about 24 percent. There are other elements

found on the Sun’s surface. Some of these elements are: oxygen, carbon, iron,
sulfur, calcium, and magnesium.
Stars follow a certain life cycle. The Sun is said to be around 4.59 billion years

old. Approximately five billion years from now, it will become a red giant. If the Sun
had more mass, it will explode as a supernova. Being a red giant, the Sun will
expand beyond the Earth’s orbit. It will grow into a red giant as the hydrogen fuel
in its core is burned, and the core heats up. At present, the core of the Sun has a
temperature of approximately 13.6 million Kelvin. The Sun produces great energy

and heat. All the heat and energy come from the Sun’s core. In its core, energy is
produced by nuclear fusion. Nuclear fusion is the process of converting
hydrogen into helium. The heat that is produced in the Sun’s core through nuclear

fusion escapes the surface of the Sun as sunlight or kinetic energy.
The Sun is very bright, so looking directly at the Sun can hurt the naked eye. It
can not only cause pain to the person looking directly at the Sun, but it can cause
serious damage to the eye as well. When a person looks directly at the Sun, the
Sun’s light can heat up the retina. This can cause damage to the eye that cannot

respond properly to the brightness of the Sun’s light. Looking directly at the Sun
for long periods can eventually burn the retina. Extreme exposure to ultraviolet
rays may also take part in causing blindness.

Main Idea

What is the main idea of this story?

a. how the sun can contribute to blindness
b. what the sun is made up of
c. what nuclear fusion is

d. some characteristics of the sun

48_Reading Success B 6