What Causes the Sun to Glow?

Like other stars, the sun is made of hot gases, such as hydrogen and helium, and plasma, which is considered the fourth state of matter. The sun has a dense core, where the temperature is 27 million degrees Fahrenheit, sufficient to merge the nuclei of atoms. This process is called thermonuclear fusion and produces a great quantity of energy in the form of radiation. The sun glows because it releases this radiation into the space. In addition to the core, the sun has five outer regions: the radiative zone, the convective zone, the photosphere, the chromosphere and the corona, which is the outermost region.
  1. Thermonuclear Fusion

    • At the sun's core, the high pressure and temperature cause atoms that would repel each other to overcome what is called "electrostatic repulsion," to merge their nuclei. The energy produced in the core through thermonuclear fusion takes 170,000 years to move from the core to the convective zone. These thermonuclear fusion reactions make the sun a giant power house, able to provide light and warmth to the Earth, which is 92.96 million miles away.

    Radiative and Convective Zones

    • The radiative zone is a dense intermediate layer between the core and the convective zone. It is called radiative because the energy travels to the outer layer in the form of radiation. The temperatures range from 14 million to about 3.5 million degrees Fahrenheit, in the outer areas. In the convective zone, temperature is lower than 3.5 million degrees Fahrenheit and large bubbles of plasma move towards the surface. Although the convective zone makes up more than 60 percent of the volume of the sun, it represents only 2 percent of the sun's mass.

    The Outermost Zones

    • With temperatures of 10,000 degrees Fahrenheit, the photosphere is the outer layer from where the sun's radiation escapes. After it leaves the sun, it takes eight minutes for the radiation to arrive to the Earth, in the form of sunlight. The chromosphere and the corona are located above the photosphere. In these outer layers, temperature increases with altitude, and can reach 3.5 million degrees Fahrenheit. During an eclipse, the chromosphere is detected as a red rim around the sun. The corona appears as an outer white crown.

    Coronal Mass Ejections and Solar Winds

    • Coronal mass ejections are constantly occurring in the corona. Coronal mass ejections are bursts of solar wind or radiation, that rises above the corona, and have roughly the energy of one billion hydrogen bombs. Solar winds travel across the solar system, and they have eroded the atmospheres of close planets, such as Mercury. The northern lights observed near the Arctic are the result of the interaction between solar winds and the Earth's atmosphere and magnetic field.

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