www.whyville.net Mar 26, 2006 Weekly Issue

Guest Writer

Up, Up and Away

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Outer space surrounds us with it's dark blackness. But it's actually not as dark as it seems . . .

We couldn't live without the sun. The sun and stars are very important in our nightly and daily life. So let me tell you about stars . . . A star is actually an enormous glowing ball of gas, not a little yellow five-pointed shape as some of us seem to think. Our sun is a medium-sized star. That's right. Not big, or small, just right.

Stars can live for billions of years! That's older than my grampa! A star is made when a cloud of hydrogen gas collapses until it is hot enough to burn nuclear fuel! In about 5 billion years, the nuclear fuel runs out and while the star expands, the core contracts, becoming a gigantic star which eventually will explode. It will then turn into a dim object; either a black dwarf, a neutron star, or a black hole. The biggest stars have the longest life span. All groups of stars are held together by gravitational forces.

Most stars occur in groups of two or more. About half of all stars are in a binary star system which is when two stars are locked into an orbit around the center of their mass (which is called the barycenter).

Clusters of stars, which are larger groups of stars are unorganized. An open cluster is a cluster of up to 1,000 stars. The Pleiads and Hyades are open clusters.

A galaxy is a huge group of stars, dust and gas bound together by gravity. Our very own solar system is located in a galaxy; The Milky Way. The Milky Way is a spiral galaxy. A spiral galaxy is a galaxy with a dense central area and spiraling arms. There are many different types of galaxies: spiral, elliptical, irregular, lenticular, active, and clusters of galaxies.

Here are some questions you may have had about stars:
Q. What is the closest star?
A. The closest star is the sun. After that comes the Proxima Centauri, also known as Alpha Centauri C. Proxima Centauri is 4.3 light-years away from the sun.

Q. Why do stars twinkle?
A. The scientific name for twinkling of stars is stellar scintillation. Stars twinkle when we view them from Earth's surface because we are looking at them through dense layers of turbulent air.

And now I'm off to do some star-gazing. You should too.


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