STARRY NIGHTS
by Gary Boyle
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June 18, 2003
OUR DAYTIME STAR
The Sun - our closest star, is a monsterous ball of flaming gas. It plays an essential part of our everyday life. We are dependent on its energy to grow crops, provide light and give us warmth. Sunlight is an important source of vitamin D and without it the human body could develop osteomalacia, resulting in muscular weakness in addition to weak bones. Trees and plants rely on solar rays for photosynthesis. Forests are vital in transforming carbon dioxide to oxygen.
Located at an average distance of one hundred and fifty million kilometers from us, the Sun’s width measures 1.4 million kilometers at its equator, in fact you can line up 109 earths side by side across this zone. Astronomers refer to this Sun / Earth distance as an astronomical unit (au). This cosmic yardstick is only used for planetary distances. Any reference outside our neighborhood of planets are ticked off in light years (ly).
If the Sun were hollow, one million Earths would fit inside. Although its width is enormous, the Sun is an average star and only one of the estimated 100 billion stars that inhabit our galaxy which we call the Milky Way. In the early days of antiquity the Greeks referred to the Sun as Helios and the Romans called it Sol.
All nine planets, of our solar system, as well as comets and asteroids were created from the left over material, which formed the Sun. Some five billion years ago in the icy depths of space, a gigantic gas cloud called the solar nebula containing interstellar dust and hydrogen gas began to collapse upon itself. This motion was possibly set off by the shockwave of a nearby exploding star called a supernova a few light years away.
For the next 100,000 years the gas cloud continues to collapse creating gravity and unimaginable heat. The intense heat caused part of the dust to vaporize. Most of the remaining gas fell onto the star thus adding to its ever growing mass. The rest formed an accretion disk around the star something like Saturn’s ring system, but a lot wider and fluffier. In this disk some gas is transformed back into dust particles which began colliding with each other until they grew to the planets we see today.
At 5 billion years old our Sun is midway through its expected 10 billion-year life span. As technology improves and with the aid of satellites in Earth orbit, astronomers are beginning to understand more and more about Sol. The closest star to our Sun is Proxima Centarus and lies 4.3 light years from us. A spacecraft using today’s technology would take about 25,000 years to reach it. Stars are like people; they develop and are eventually born, live longer or shorter lives, burn at different temperatures and portray various characteristics. With this said, if we did break the light travel barrier, we could study different types of stars other than our Sun. However for now we are content in studying and carefully scrutinizing its solar secrets.
The Sun has three layers the first of which is called the photosphere and is only 100 km thick. This layer registers 5,800° C and is home to sunspots. These dark blemishes as seen with a telescope with a safe solar filter are cooler magnetic regions (4,600° C) and measures thousands of times the strength of Earth’s magnetism. Resembling a sunflower on Earth, the inside black area called the umbra has a high magnetic field. The outer petal like feature – the penumbra is lower in magnetism.
The next layer above the photosphere is called the chromosphere with temperatures rising up to 15,000° C. Appearing like the hair on your arm, spicules rises to approximately 3,000 miles or 5,000 km above the photosphere and lasts only a few minutes. This is where solar flares and prominces emanate from. These flares occur when built up magnetic energy in the solar atmosphere is suddenly released like the snapping of a rubber band. Large flares can emit energy as much as ten million times greater than the energy released from an exploding volcano.
If a flare containing charged particles should hit the Earth, we could witness a beautiful display of northern lights – the aurora borealis. An aurora occurs when the solar particles react with our planet’s magnetic field at the poles and begin to glow, much like a neon light. The Sun is presently at the active portion of its 11-year solar cycle called solar max. For the next year the sun will be extremely active producing many giant flares and thus a greater chance on seeing an aurora.
The third and final layer is not near the surface but circling the solar disk. Only seen during a total solar eclipse, the corona appears as a halo and is slowly being understood by astronomers. The most puzzling aspect of it is the blistering one to two million-degree temperature.
Tapping the Sun’s output is an economical power alternative. Solar cells are gaining in popularity as they are used in calculators and even heating water for homes and buildings. It has been estimated that if we were to harness the energy of the entire Sun for only one second, it would satisfy the entire power requirements of North America for over 3 million years. Nuclear fusion on the solar surface produces about 386 billion megawatts of power per second.
Alas though, the Sun will use up its fuel supply and die out. It will not explode but expand like a balloon to red giant status. Growing from the present 1.4 million kilometers to half a billion kilometers in size, it will vaporize Mercury, Venus, Earth and Mars. The latter stages of its death the Sun will become a planetary nebula, casting off its outer shell of gas in a beautiful halo around a faint cooler Sun.
