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updated: 2/1/2011 2:12 PM

Sun still has a few billion years left to shine

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  • This sundial at the Adler Planetarium in Chicago can chart the sun's position in the sky. The sun is about 5 billion years old.

    This sundial at the Adler Planetarium in Chicago can chart the sun's position in the sky. The sun is about 5 billion years old.
    Courtesy Adler Planetarium


Students in Katherine Crawford's fifth-grade classroom at West Oak Middle School in Mundelein asked: "Will the sun burn out?"

The sun was formed about 5 billion years ago, and the sun will burn out in about another 5 billion years, according to Geza Gyuk, director of the Adler Planetarium.

"We have plenty of time still," Gyuk said.

The process of the birth of the sun took a few million years. It all began when a cloud of gas and dust was somehow disturbed, causing the cloud to collapse under its own weight.

"As it collapsed, the center grew denser and hotter. Eventually, it grew so hot and dense that nuclear fusion ignited as hydrogen atoms slammed together hard enough and frequently enough that helium was produced. This process stopped the collapse of the sun's core, and after a few million years, things settled down," Gyuk said.

The sun is the primary source of heat and energy for Earth. It also influences changes in Earth's atmosphere. Those and other factors helped Earth's plant and animal life to develop.

The nuclear reactions have continued, causing helium ash to settle in the sun's core. "Eventually, enough helium will accumulate that it will start to fuse to carbon. At that point the sun will have two sources of energy and will start to expand. Eventually it will form a Red Giant, ballooning to 100 times larger in radius," Gyuk said.

Some Red Giants you may have heard of are Betelgeuse and Antares, two of the brightest stars in the skies.

Without the sun, Earth would be in total darkness, lose most of its heat, and most plant life and animal life would become extinct. Gyuk points out that we may not have to worry about the negative effects of the sun's final years.

"It is quite possible that it will swallow up the earth as it grows. In any event, it will sterilize the earth with its heat and light."

What will happen to the sun once it completes its full cycle?

Gyuk explained: "All that will be left is the core of carbon weighing about half as much as the sun does today. This core will be a white dwarf. It will slowly cool over billions of years, and as it does, its surface will crystallize. Crystallized carbon is a diamond, so it is not completely wrong to think of the sun ending up as a planet-sized, super dense diamond."

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